UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K



(X)		Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for the fiscal year ended December 31, 2012.

		OR

( )		Transition report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 for the transition period from to .



Commission File Number	Exact name of registrant as specified in its charter; State of Incorporation; Address and Telephone Number	IRS Employer Identification No.

1-14756	Ameren Corporation	43-1723446
	(Missouri Corporation)
	1901 Chouteau Avenue
	St. Louis, Missouri 63103
	(314) 621-3222

1-2967	Union Electric Company	43-0559760
	(Missouri Corporation)
	1901 Chouteau Avenue
	St. Louis, Missouri 63103
	(314) 621-3222

1-3672	Ameren Illinois Company	37-0211380
	(Illinois Corporation)
	6 Executive Drive
	Collinsville, Illinois 62234
	(618) 343-8039

Securities Registered Pursuant to Section 12(b) of the Act:

The following security is registered pursuant to Section 12(b) of the Securities Exchange Act of 1934 and is listed on the New York Stock Exchange:



Registrant		Title of each class
Ameren Corporation		Common Stock, $0.01 par value per share

Securities Registered Pursuant to Section 12(g) of the Act:



Registrant		Title of each class
Union Electric Company		Preferred Stock, cumulative, no par value, stated value $100 per share
Ameren Illinois Company		Preferred Stock, cumulative, $100 par value per share Depository Shares, each representing one-fourth of a share of 6.625% Preferred Stock, cumulative, $100 par value per share

Indicate by checkmark if each registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.



Ameren Corporation	Yes	(X)	No	( )
Union Electric Company	Yes	( )	No	(X)
Ameren Illinois Company	Yes	( )	No	(X)

Indicate by checkmark if each registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act.



Ameren Corporation	Yes	( )	No	(X)
Union Electric Company	Yes	( )	No	(X)
Ameren Illinois Company	Yes	( )	No	(X)

Indicate by checkmark whether the registrants: (1) have filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) have been subject to such filing requirements for the past 90 days.



Ameren Corporation	Yes	(X)	No	( )
Union Electric Company	Yes	(X)	No	( )
Ameren Illinois Company	Yes	(X)	No	( )

Indicate by checkmark whether each registrant has submitted electronically and posted on its corporate website, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).



Ameren Corporation	Yes	(X)	No	( )
Union Electric Company	Yes	(X)	No	( )
Ameren Illinois Company	Yes	(X)	No	( )

Indicate by checkmark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§ 229.405 of this chapter) is not contained herein, and will not be contained, to the best of each registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.



Ameren Corporation		(X)
Union Electric Company		(X)
Ameren Illinois Company		(X)

Indicate by checkmark whether each registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer or a smaller reporting company. See definitions of “large accelerated filer,” “accelerated filer,” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.



	Large Accelerated Filer	Accelerated Filer	Non-accelerated Filer	Smaller Reporting Company
Ameren Corporation	(X)	( )	( )	( )
Union Electric Company	( )	( )	(X)	( )
Ameren Illinois Company	( )	( )	(X)	( )

Indicate by checkmark whether each registrant is a shell company (as defined in Rule 12b-2 of the Act).



Ameren Corporation	Yes	( )	No	(X)
Union Electric Company	Yes	( )	No	(X)
Ameren Illinois Company	Yes	( )	No	(X)

As of June 29, 2012, Ameren Corporation had 242,634,671 shares of its $0.01 par value common stock outstanding. The aggregate market value of these shares of common stock (based upon the closing price of the common stock on the New York Stock Exchange on June 29, 2012) held by nonaffiliates was $8,137,966,865. The shares of common stock of the other registrants were held by Ameren Corporation as of June 29, 2012.

The number of shares outstanding of each registrant’s classes of common stock as of January 31, 2013, was as follows:



Ameren Corporation	Common stock, $0.01 par value per share: 242,634,671

Union Electric Company	Common stock, $5 par value per share, held by Ameren Corporation (parent company of the registrant): 102,123,834

Ameren Illinois Company	Common stock, no par value, held by Ameren Corporation (parent company of the registrant): 25,452,373

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the definitive proxy statement of Ameren Corporation and portions of the definitive information statements of Union Electric Company and Ameren Illinois Company for the 2013 annual meetings of shareholders are incorporated by reference into Part III of this Form 10-K.

This combined Form 10-K is separately filed by Ameren Corporation, Union Electric Company, and Ameren Illinois Company. Each registrant hereto is filing on its own behalf all of the information contained in this annual report that relates to such registrant. Each registrant hereto is not filing any information that does not relate to such registrant, and therefore makes no representation as to any such information.

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TABLE OF CONTENTS



		Page
GLOSSARY OF TERMS AND ABBREVIATIONS		1
Forward-looking Statements		3
PART I
Item 1.	Business	5
	General	5
	Business Segments	5
	Rates and Regulation	5
	Transmission and Supply of Electric Power	10
	Power Generation	11
	Natural Gas Supply for Distribution	14
	Industry Issues	14
	Operating Statistics	16
	Available Information	18
Item 1A.	Risk Factors	18
Item 1B.	Unresolved Staff Comments	26
Item 2.	Properties	27
Item 3.	Legal Proceedings	28
Item 4.	Mine Safety Disclosures	29
Executive Officers of the Registrants (Item 401(b) of Regulation S-K)		29

PART II
Item 5.	Market for Registrants’ Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities	31
Item 6.	Selected Financial Data	33
Item 7.	Management’s Discussion and Analysis of Financial Condition and Results of Operations	34
	Overview	34
	Results of Operations	35
	Liquidity and Capital Resources	54
	Outlook	69
	Regulatory Matters	74
	Accounting Matters	75
	Effects of Inflation and Changing Prices	77
Item 7A.	Quantitative and Qualitative Disclosures About Market Risk	78
Item 8.	Financial Statements and Supplementary Data	83
	Selected Quarterly Information	173
Item 9.	Changes in and Disagreements with Accountants on Accounting and Financial Disclosure	173
Item 9A.	Controls and Procedures	173
Item 9B.	Other Information	174

PART III
Item 10.	Directors, Executive Officers and Corporate Governance	174
Item 11.	Executive Compensation	175
Item 12.	Security Ownership of Certain Beneficial Owners and Management and Related Stockholder Matters	175
Item 13.	Certain Relationships and Related Transactions and Director Independence	175
Item 14.	Principal Accounting Fees and Services	176

PART IV
Item 15.	Exhibits and Financial Statement Schedules	176
SIGNATURES		181
EXHIBIT INDEX		184

This report contains “forward-looking” statements within the meaning of Section 21E of the Securities Exchange Act of 1934, as amended. Forward-looking statements should be read with the cautionary statements and important factors included on pages 4 and 5 of this report under the heading “Forward-looking Statements.” Forward-looking statements are all statements other than statements of historical fact, including those statements that are identified by the use of the words “anticipates,” “estimates,” “expects,” “intends,” “plans,” “predicts,” “projects,” and similar expressions.

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GLOSSARY OF TERMS AND ABBREVIATIONS

We use the words “our,” “we” or “us” with respect to certain information that relates to all Ameren Companies, as defined below. When appropriate, subsidiaries of Ameren are named specifically as we discuss their various business activities.

2007 Illinois Electric Settlement Agreement - A comprehensive settlement of issues in Illinois arising out of the end of ten years of frozen electric rates. The settlement, which became effective in 2007, was designed to avoid rate rollback and freeze legislation and legislation that would have imposed a tax on electric generation in Illinois. The settlement addressed the issue of power procurement.

2010 Credit Agreements - The 2010 Genco Credit Agreement, the 2010 Illinois Credit Agreement, and the 2010 Missouri Credit Agreement, collectively, which terminated on November 14, 2012.

2010 Genco Credit Agreement - Ameren’s and Genco’s $500 million multiyear senior unsecured credit agreement, which was terminated on November 14, 2012.

2010 Illinois Credit Agreement - Ameren’s and Ameren Illinois’ $800 million multiyear senior unsecured credit agreement, which was terminated on November 14, 2012.

2010 Missouri Credit Agreement - Ameren’s and Ameren Missouri’s $800 million multiyear senior unsecured credit agreement, which was terminated on November 14, 2012.

2012 Credit Agreements - The 2012 Illinois Credit Agreement and the 2012 Missouri Credit Agreement, collectively.

2012 Illinois Credit Agreement - Ameren's and Ameren Illinois' $1.1 billion multiyear senior unsecured credit agreement, which expires on November 14, 2017.

2012 Missouri Credit Agreement - Ameren's and Ameren Missouri's $1 billion multiyear senior unsecured credit agreement, which expires on November 14, 2017.

AER - AmerenEnergy Resources Company, LLC, an Ameren Corporation subsidiary that consists of non-rate-regulated operations, including Genco, AERG, Marketing Company and Medina Valley. The Medina Valley energy center was sold in February 2012. On October 1, 2010, AERG stock was distributed to Ameren, which then contributed it to AER, thereby making AERG a subsidiary of AER.

AERG - Ameren Energy Resources Generating Company, a CILCO subsidiary until October 1, 2010, that operates a merchant electric generation business in Illinois. On October 1, 2010, AERG stock was distributed to Ameren and subsequently contributed by Ameren to AER, which resulted in AERG becoming a subsidiary of AER.

AFS - Ameren Energy Fuels and Services Company, an AER subsidiary that procured fuel and natural gas and managed the related risks for the Ameren Companies prior to January 1, 2011. Effective January 1, 2011, the functions previously performed by AFS were assumed by the Ameren Missouri, Ameren Illinois and Merchant Generation business segments.

Ameren - Ameren Corporation and its subsidiaries on a consolidated basis. In references to financing activities, acquisition activities, or liquidity arrangements, Ameren is defined as Ameren Corporation, the parent.

Ameren Companies - Ameren Corporation, Ameren Missouri, and Ameren Illinois, collectively, which are individual registrants within the Ameren consolidated group.

Ameren Illinois or AIC - Ameren Illinois Company, an Ameren Corporation subsidiary that operates a rate-regulated electric and natural gas transmission and distribution business in Illinois, doing business as Ameren Illinois. This business consists of the combined rate-regulated electric and natural gas transmission and distribution businesses operated by CIPS, CILCO and IP before the Ameren Illinois Merger. References to Ameren Illinois prior to the Ameren Illinois Merger refer collectively to the rate-regulated electric and natural gas transmission and distribution businesses of CIPS, CILCO and IP. Immediately after the Ameren Illinois Merger, Ameren Illinois distributed the common stock of AERG to Ameren Corporation. AERG’s operating results and cash flows prior to October 1, 2010, were presented as discontinued operations in Ameren Illinois’ financial statements. Ameren Illinois is also defined as a financial reporting segment beginning after 2010.

Ameren Illinois Merger - On October 1, 2010, CILCO and IP merged with and into CIPS, with the surviving corporation renamed Ameren Illinois Company.

Ameren Illinois Segment - A financial reporting segment consisting of Ameren Illinois’ rate-regulated businesses.

Ameren Missouri or AMO - Union Electric Company, an Ameren Corporation subsidiary that operates a rate-regulated electric generation, transmission and distribution business, and a rate-regulated natural gas transmission and distribution business in Missouri, doing business as Ameren Missouri. Ameren Missouri is also defined as a financial reporting segment.

Ameren Services - Ameren Services Company, an Ameren Corporation subsidiary that provides support services to Ameren and its subsidiaries.

AMIL - The MISO balancing authority area operated by Ameren, which includes the load of Ameren Illinois and the Merchant Generation energy centers (excluding EEI and Elgin CT energy centers).

AMMO - The MISO balancing authority area operated by Ameren, which includes the load and generation energy centers of Ameren Missouri.

ARO - Asset retirement obligations.

ATXI - Ameren Transmission Company of Illinois, an Ameren Corporation subsidiary that is engaged in the construction and operation of electric transmission assets.

Baseload - The minimum amount of electric power delivered or required over a given period of time at a steady rate.

Btu - British thermal unit, a standard unit for measuring the quantity of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit.

CAIR - Clean Air Interstate Rule.

Capacity factor - A percentage measure that indicates how much of an energy center's capacity was used during a specific period.

CCR - Coal combustion residuals.

CILCO - Central Illinois Light Company, a former Ameren Corporation subsidiary that operated a rate-regulated electric transmission and distribution business, a merchant electric

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generation business through AERG, and a rate-regulated natural gas transmission and distribution business, all in Illinois, before the Ameren Illinois Merger. CILCO owned all of the common stock of AERG and included AERG within its consolidated financial statements. Immediately after the Ameren Illinois Merger in 2010, Ameren Illinois distributed the common stock of AERG to Ameren Corporation. AERG's operating results and cash flows prior to October 1, 2010, were presented as discontinued operations in Ameren Illinois’ financial statements.

CILCORP - CILCORP Inc., a former Ameren Corporation subsidiary that operated as a holding company for CILCO and its merchant generation subsidiary. On March 4, 2010, CILCORP merged with and into Ameren.

CIPS - Central Illinois Public Service Company, an Ameren Corporation subsidiary, renamed Ameren Illinois Company at the effective date of the Ameren Illinois Merger, which operates a rate-regulated electric and natural gas transmission and distribution business, all in Illinois.

CO₂ - Carbon dioxide.

COL - Nuclear energy center combined construction and operating license.

Cole County Circuit Court - Circuit Court of Cole County, Missouri.

Cooling degree-days - The summation of positive differences between the mean daily temperature and a 65-degree Fahrenheit base. This statistic is useful as an indicator of electricity demand by residential and commercial customers for summer cooling.

CSAPR - Cross-State Air Pollution Rule.

CT - Combustion turbine electric energy center used primarily for peaking capacity.

DOE - Department of Energy, a United States government agency.

DRPlus - Ameren Corporation’s dividend reinvestment and direct stock purchase plan.

Dekatherm - One million Btus of natural gas.

EEI - Electric Energy, Inc., an 80%-owned Genco subsidiary that operates merchant electric generation energy centers and FERC-regulated transmission facilities in Illinois. The remaining 20% ownership interest is owned by Kentucky Utilities Company, a nonaffiliated entity.

Entergy - Entergy Arkansas, Inc.

EPA - Environmental Protection Agency, a United States government agency.

Equivalent availability factor - A measure that indicates the percentage of time an energy center was available for service during a period.

ERISA - Employee Retirement Income Security Act of 1974, as amended.

Exchange Act - Securities Exchange Act of 1934, as amended.

FAC - A fuel and purchased power cost recovery mechanism that allows Ameren Missouri to recover, through customer rates, 95% of changes in fuel (coal, coal transportation, natural gas for generation, and nuclear), certain fuel additives, emission allowances, purchased power costs, transmission costs and MISO costs and revenues, net of off-system revenues, greater or less than the amount set in base rates without a traditional rate proceeding, subject to MoPSC prudency reviews. The MoPSC's December 2012 electric rate order changed the FAC to include activated carbon, limestone and urea costs, along with

transmission revenues, starting in 2013.

FASB - Financial Accounting Standards Board, a rulemaking organization that establishes financial accounting and reporting standards in the United States.

FERC - Federal Energy Regulatory Commission, a United States government agency.

Fitch - Fitch Ratings, a credit rating agency.

FTRs - Financial transmission rights, financial instruments that entitle the holder to pay or receive compensation for certain congestion-related transmission charges between two designated points.

Fuelco - Fuelco LLC, a limited liability company that provides nuclear fuel management and services to its members. The members are Ameren Missouri, Luminant, and Pacific Gas and Electric Company.

GAAP - Generally accepted accounting principles in the United States of America.

Genco - Ameren Energy Generating Company, an AER subsidiary that operates a merchant electric generation business in Illinois and holds an 80% ownership interest in EEI.

Heating degree-days - The summation of negative differences between the mean daily temperature and a 65-degree Fahrenheit base. This statistic is useful as an indicator of demand for electricity and natural gas for winter space heating by residential and commercial customers.

IBEW - International Brotherhood of Electrical Workers, a labor union.

ICC - Illinois Commerce Commission, a state agency that regulates Illinois utility businesses, including Ameren Illinois and ATXI.

IEIMA - Illinois Energy Infrastructure Modernization Act, an Illinois law that established a performance-based formula process for determining electric delivery service rates. Ameren Illinois elected to participate in this regulatory framework in 2012, which will require it to make incremental capital expenditures to modernize its electric distribution system over a ten-year period, to meet performance standards, and to create jobs in Illinois, among other things.

Illinois Customer Choice Law - Illinois Electric Service Customer Choice and Rate Relief Law of 1997, which was designed to introduce competition into the retail supply of electric energy in Illinois.

IP - Illinois Power Company, a former Ameren Corporation subsidiary that operated a rate-regulated electric and natural gas transmission and distribution business, all in Illinois, before the Ameren Illinois Merger.

IPA - Illinois Power Agency, a state government agency that has broad authority to assist in the procurement of electric power for residential and small commercial customers.

ISRS - Infrastructure system replacement surcharge, which is a cost recovery mechanism that allows Ameren Missouri to recover natural gas infrastructure replacement costs from utility customers without a traditional rate proceeding.

IUOE - International Union of Operating Engineers, a labor union.

Kilowatthour - A measure of electricity consumption equivalent to the use of 1,000 watts of power over one hour.

LIUNA - Laborers’ International Union of North America, a labor union.

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Marketing Company - Ameren Energy Marketing Company, an AER subsidiary that markets power for Genco, AERG, and EEI.

MATS - Mercury and Air Toxics Standards.

Medina Valley - Ameren Energy Medina Valley Cogen LLC, an AER subsidiary, which owned a 40-megawatt natural gas-fired electric energy center. This energy center was sold in February 2012.

MEEIA -- Missouri Energy Efficiency Investment Act, a Missouri law that allows electric utilities to recover costs related to MoPSC-approved energy efficiency programs.

Megawatthour or MWh - One thousand kilowatthours.

Merchant Generation - A financial reporting segment consisting primarily of the operations of AER, including Genco, AERG, Medina Valley and Marketing Company.

MGP - Manufactured gas plant.

MIEC - Missouri Industrial Energy Consumers.

MISO - Midwest Independent Transmission System Operator, Inc., an RTO.

MISO Energy and Operating Reserves Market - A market that uses market-based pricing, which takes into account transmission congestion and line losses, to compensate market participants for power and ancillary services.

Missouri Environmental Authority - Environmental Improvement and Energy Resources Authority of the state of Missouri, a governmental body authorized to finance environmental projects by issuing tax-exempt bonds and notes.

Mmbtu - One million Btus.

Money pool - Borrowing agreements among Ameren and its subsidiaries to coordinate and provide for certain short-term cash and working capital requirements. Separate money pools maintained for rate-regulated and non-rate-regulated businesses are referred to as the utility money pool and the non-state-regulated subsidiary money pool, respectively.

Moody’s - Moody’s Investors Service Inc., a credit rating agency.

MoOPC - Missouri Office of Public Counsel.

MoPSC - Missouri Public Service Commission, a state agency that regulates Missouri utility businesses including Ameren Missouri.

MPS - Multi-Pollutant Standard, a compliance alternative within Illinois law covering reductions in emissions of SO_2,NO_x, and mercury, which Genco, EEI, and AERG elected in 2006.

MTM - Mark-to-market.

MW - Megawatt.

Native load - End-use retail customers whom we are obligated to serve by statute, franchise, contract, or other regulatory requirement.

NERC - North American Electric Reliability Corporation.

NO₂ - Nitrogen dioxide.

NO_x - Nitrogen oxide.

Noranda - Noranda Aluminum, Inc.

NPNS - Normal purchases and normal sales.

NRC - Nuclear Regulatory Commission, a United States government agency.

NSPS - New Source Performance Standards, a provision under the Clean Air Act.

NSR - New Source Review provisions of the Clean Air Act, which include Nonattainment New Source Review and Prevention of Significant Deterioration regulations.

NWPA - Nuclear Waste Policy Act of 1982, as amended.

NYMEX - New York Mercantile Exchange.

NYSE - New York Stock Exchange, Inc.

OATT - Open Access Transmission Tariff.

OCI - Other comprehensive income (loss) as defined by GAAP.

Off-system revenues - Revenues from other than native load sales, including wholesale sales beginning with the effective date of the MoPSC’s 2011 electric rate order.

OTC - Over-the-counter.

PGA - Purchased Gas Adjustment tariffs, which permit prudently incurred natural gas costs to be recovered directly from utility customers without a traditional rate proceeding.

PJM - PJM Interconnection LLC.

PUHCA 2005 - The Public Utility Holding Company Act of 2005.

Regulatory lag - The effect of adjustments to retail electric and natural gas rates being based on historic cost and revenue levels. Rate increase requests can take up to 11 months to be acted upon by the MoPSC and the ICC. As a result, revenue increases authorized by regulators will lag behind changing costs and revenues when based on historical periods.

Revenue requirement - The cost of providing utility service to customers, which is calculated as the sum of a utility's recoverable operating and maintenance expenses, depreciation and amortization expense, taxes and an allowed return on investment.

RFP - Request for proposal.

RTO - Regional Transmission Organization.

S&P - Standard & Poor’s Ratings Services, a credit rating agency.

SEC - Securities and Exchange Commission, a United States government agency.

SERC - SERC Reliability Corporation, one of the regional electric reliability councils organized for coordinating the planning and operation of the nation’s bulk power supply.

SO₂_- Sulfur dioxide.

Stoddard County Circuit Court - Circuit Court of Stoddard County, Missouri.

UA - United Association of Plumbers and Pipefitters, a labor union.

Westinghouse - Westinghouse Electric Company.

FORWARD-LOOKING STATEMENTS

Statements in this report not based on historical facts are considered “forward-looking” and, accordingly, involve risks and uncertainties that could cause actual results to differ materially from those discussed. Although such forward-looking statements have been made in good faith and are based on reasonable assumptions, there is no assurance that the expected results will be achieved. These statements include (without limitation) statements as to future expectations, beliefs, plans, strategies, objectives, events, conditions, and financial performance. In connection with the “safe harbor” provisions of the Private Securities Litigation Reform Act of 1995, we are providing this cautionary statement to identify important factors that could cause actual results to differ materially from those anticipated.

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The following factors, in addition to those discussed under Risk Factors and elsewhere in this report and in our other filings with the SEC, could cause actual results to differ materially from management expectations suggested in such forward-looking statements:

•

regulatory, judicial, or legislative actions, including changes in regulatory policies and ratemaking determinations, such as the outcome of Ameren Illinois' natural gas rate case filed in 2013; the court appeals of Ameren Missouri's and Ameren Illinois' electric rate orders issued in 2012; Ameren Missouri's FAC prudence review and the related request for an accounting authority order; Ameren Illinois' request for rehearing of a July 2012 FERC order regarding the inclusion of acquisition premiums in Ameren Illinois transmission rates; and future regulatory, judicial, or legislative actions that seek to change regulatory recovery mechanisms;


•	the effect of Ameren Illinois participating in a performance-based formula ratemaking process under the IEIMA, the related financial commitments required by the IEIMA, and the resulting uncertain impact on the financial condition, results of operations and liquidity of Ameren Illinois;


•	Ameren's eventual exit from the Merchant Generation business could result in impairments of long-lived assets, disposal-related losses, contingencies, reduction of existing deferred tax assets, or could have other adverse impacts on the financial condition, results of operations and liquidity of Ameren;


•	the effects of, or changes to, the Illinois power procurement process;


•	changes in laws and other governmental actions, including monetary, fiscal, and tax policies;


•	changes in laws or regulations that adversely affect the ability of electric distribution companies and other purchasers of wholesale electricity to pay their suppliers, including Ameren Missouri and Marketing Company;


•	the effects of increased competition in the future due to, among other things, deregulation of certain aspects of our business at both the state and federal levels, and the implementation of deregulation;


•	the effects on demand for our services resulting from technological advances, including advances in energy efficiency and distributed generation sources, which generate electricity at the site of consumption;


•	increasing capital expenditure and operating expense requirements and our ability to recover these costs;


•	the cost and availability of fuel such as coal, natural gas, and enriched uranium used to produce electricity; the cost and availability of purchased power and natural gas for distribution; and the level and volatility of future market prices for such commodities, including the ability to recover the costs for such commodities;


•	the effectiveness of our risk management strategies and the use of financial and derivative instruments;


•	the level and volatility of future prices for power in the Midwest, which may have a significant effect on the financial condition of Ameren's Merchant Generation segment;


•	the development of a multiyear capacity market within MISO and the outcomes of MISO's inaugural annual capacity

auction in 2013;


•	business and economic conditions, including their impact on interest rates, bad debt expense, and demand for our products;


•	disruptions of the capital markets, deterioration in credit metrics of the Ameren Companies, or other events that make the Ameren Companies' access to necessary capital, including short-term credit and liquidity, impossible, more difficult, or more costly;


•	our assessment of our liquidity, including liquidity concerns for Ameren's Merchant Generation business, and specifically for Genco, which has limited access to third-party financing sources;


•	the impact of the adoption of new accounting guidance and the application of appropriate technical accounting rules and guidance;


•	actions of credit rating agencies and the effects of such actions;


•	the impact of weather conditions and other natural phenomena on us and our customers, including the impacts of droughts, which may cause lower river levels and could limit our energy centers' ability to generate power;


•	the impact of system outages;


•	generation, transmission, and distribution asset construction, installation, performance, and cost recovery;


•	the effects of our increasing investment in electric transmission projects and uncertainty as to whether we will achieve our expected returns in a timely fashion, if at all;


•	the extent to which Ameren Missouri prevails in its claims against insurers in connection with its Taum Sauk pumped-storage hydroelectric energy center incident;


•	the extent to which Ameren Missouri is permitted by its regulators to recover in rates the investments it made in connection with additional nuclear generation at its Callaway energy center;


•	operation of Ameren Missouri's Callaway energy center, including planned and unplanned outages, and decommissioning costs;


•	the effects of strategic initiatives, including mergers, acquisitions and divestitures, and any related tax implications;

•

the impact of current environmental regulations on utilities and power generating companies and new, more stringent or changing requirements, including those related to greenhouse gases, other emissions, cooling water intake structures, CCR, and energy efficiency, that are enacted over time and that could limit or terminate the operation of certain of our energy centers, increase our costs, result in an impairment of our assets, reduce our customers' demand for electricity or natural gas, or otherwise have a negative financial effect;


•	the impact of complying with renewable energy portfolio requirements in Missouri;


•	labor disputes, workforce reductions, future wage and employee benefits costs, including changes in discount rates and returns on benefit plan assets;


•	the inability of our counterparties and affiliates to meet their obligations with respect to contracts, credit agreements, and financial instruments;

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•	the cost and availability of transmission capacity for the energy generated by Ameren's and Ameren Missouri's energy centers or required to satisfy energy sales made by Ameren or Ameren Missouri;


•	legal and administrative proceedings; and


•	acts of sabotage, war, terrorism, cybersecurity attacks or intentionally disruptive acts.

Given these uncertainties, undue reliance should not be placed on these forward-looking statements. Except to the extent required by the federal securities laws, we undertake no obligation to update or revise publicly any forward-looking statements to reflect new information or future events.

PART I


ITEM 1.	BUSINESS

GENERAL

Ameren, headquartered in St. Louis, Missouri, is a public utility holding company under PUHCA 2005, administered by FERC. Ameren was formed in 1997 by the merger of Ameren Missouri and CIPSCO Inc. Ameren acquired CILCORP in 2003 and IP in 2004. Ameren’s primary assets are its equity interests in its subsidiaries, including Ameren Missouri, Ameren Illinois and AER. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. These subsidiaries operate, as the case may be, rate-regulated electric generation, transmission, and distribution businesses, rate-regulated natural gas transmission and distribution businesses, and merchant generation businesses in Missouri and Illinois. Dividends on Ameren’s common stock and the payment of other expenses by Ameren depend on distributions made to it by its subsidiaries. In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business's long-lived assets. This determination resulted from Ameren’s analysis of the current and projected future financial condition of its Merchant Generation business segment, including the need to fund Genco debt maturities beginning in 2018 and its conclusion that this business segment is no longer a core component of its future business strategy. In consideration of this determination, Ameren has begun planning to reduce, and ultimately eliminate, the Merchant Generation segment's reliance on Ameren's financial support and shared services support. Ameren intends to allocate its capital resources to those business opportunities, including electric and natural gas transmission, which offer the most attractive risk-adjusted return potential.

Below is a summary description of Ameren Missouri, Ameren Illinois and AER. A more detailed description can be found in Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of this report.


•	Ameren Missouri operates a rate-regulated electric generation, transmission and distribution business, and a rate-regulated natural gas transmission and distribution business in Missouri.


•	Ameren Illinois operates a rate-regulated electric and natural gas transmission and distribution business in Illinois.


•	AER consists of non-rate-regulated operations, including Genco, AERG, Marketing Company, and, through Genco, an 80% ownership interest in EEI, which Ameren consolidates for financial reporting purposes.

The following table presents our total employees at December 31, 2012:



Ameren^(a)	9,097
Ameren Missouri	3,997
Ameren Illinois	2,994
AER	713
Ameren Services	1,393


(a)	Total for Ameren includes Ameren registrant and nonregistrant subsidiaries.

As of January 1, 2013, the IBEW, the IUOE, the LIUNA, and the UA labor unions collectively represented about 57% of Ameren’s total employees. They represented 64% of the employees at Ameren Missouri and 63% at Ameren Illinois. The collective bargaining agreements have three- to five-year terms, and expire between 2013 and 2016. Several collective bargaining agreements between Ameren subsidiaries and the IBEW, IUOE, the LIUNA and the UA labor unions, covering approximately 2,900 employees expire during 2013.

For additional information about the development of our businesses, our business operations, and factors affecting our operations and financial position, see Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report and Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of this report.

BUSINESS SEGMENTS

Ameren has three reporting segments: Ameren Missouri, Ameren Illinois, and Merchant Generation. See Note 18 – Segment Information under Part II, Item 8, of this report for additional information on reporting segments.

RATES AND REGULATION

Rates

The rates that Ameren Missouri and Ameren Illinois are

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allowed to charge for their utility services significantly influence the results of operations, financial position, and liquidity of these companies and Ameren. The electric and natural gas utility industry is highly regulated. The utility rates charged to Ameren Missouri and Ameren Illinois customers are determined, in large part, by governmental entities, including the MoPSC, the ICC, and FERC. Decisions by these entities are influenced by many factors, including the cost of providing service, the prudency of expenditures, the quality of service, regulatory staff knowledge and experience, economic conditions, public policy, and social and political views. Decisions made by these governmental entities regarding rates are largely outside of Ameren Missouri’s and Ameren Illinois’ control. These decisions, as well as the regulatory lag involved in filing and getting new rates approved, could have a material impact on the results of operations, financial position, and liquidity of Ameren, Ameren Missouri and Ameren Illinois. Rate orders are also subject to appeal, which creates additional uncertainty as to the rates Ameren Missouri and Ameren Illinois are ultimately allowed to charge for their services. The effect of regulatory lag on Ameren Illinois’ electric distribution business is mitigated to some extent through the use of the formula ratemaking regulatory framework established under the IEIMA. Beginning in 2013, regulatory lag on Ameren Illinois' and ATXI's electric transmission business will be mitigated to some extent through the use of the FERC revenue requirement reconciliation. To mitigate regulatory lag on Ameren Illinois' natural gas distribution business, recent rate requests have been filed with the ICC using a future test year.

The ICC regulates rates and other matters for Ameren Illinois and ATXI. The MoPSC regulates rates and other matters for Ameren Missouri. The FERC regulates Ameren Missouri, Ameren Illinois, ATXI, Genco, EEI, and AERG as to their ability to charge market-based rates for the sale and transmission of energy in interstate commerce and various other matters discussed below under General Regulatory Matters.

About 53% of Ameren’s electric and 15% of its natural gas operating revenues were subject to regulation by the MoPSC in the year ended December 31, 2012. About 29% of Ameren’s electric and 85% of its natural gas operating revenues were subject to regulation by the ICC in the year ended December 31, 2012. Wholesale revenues for Ameren Missouri, Ameren Illinois, Genco, Marketing Company and AERG are subject to FERC regulation, but not subject to direct MoPSC or ICC regulation.

Ameren Missouri

Electric

Almost 100% of Ameren Missouri’s electric operating revenues were subject to regulation by the MoPSC in the year ended December 31, 2012.

In December 2012, the MoPSC issued an order approving an increase for Ameren Missouri in annual revenues for electric service of $260 million, including $84 million related to an anticipated increase in normalized net fuel costs above the net fuel costs included in base rates previously authorized by the MoPSC in its July 2011 electric rate order. The annual increase

also included $80 million for recovery of the costs associated with energy efficiency programs under the MEEIA. The remaining annual increase of $96 million approved by the MoPSC was for energy infrastructure investments and other non-fuel costs, including $10 million for increased pension and other post-employment benefit costs and $6 million for increased amortization of regulatory assets. The revenue increase was based on a 9.8% return on equity, a capital structure composed of 52.3% common equity, and a rate base of $6.8 billion. The new rates became effective on January 2, 2013.

If certain criteria are met, Ameren Missouri’s electric rates may be adjusted without a traditional rate proceeding. The FAC permits 95% of prudently incurred fuel, emission allowances, purchased power costs, transmission costs and MISO costs and revenues to be passed directly to customers. The MoPSC's December 2012 electric rate order changed the FAC to include activated carbon, limestone and urea costs, along with transmission revenues, starting in 2013.

FERC regulates the rates charged and the terms and conditions for electric transmission services. Each RTO separately files a regional transmission tariff for approval by FERC. All transmission service within that RTO is then subjected to that tariff. As a member of MISO, Ameren Missouri’s transmission rate is calculated in accordance with the MISO OATT. The transmission rate is updated in June of each year; it is based on Ameren Missouri’s filings with FERC. This rate is not directly charged to Missouri retail customers, because in Missouri the MoPSC includes transmission-related costs and revenues in setting bundled retail rates.

Natural Gas

All of Ameren Missouri’s natural gas operating revenues were subject to regulation by the MoPSC in the year ended December 31, 2012. In January 2011, the MoPSC approved a stipulation and agreement that allowed Ameren Missouri to increase annual natural gas revenues by $9 million.

If certain criteria are met, Ameren Missouri’s natural gas rates may be adjusted without a traditional rate proceeding. PGA clauses permit prudently incurred natural gas costs to be passed directly to customers. The ISRS also permits prudently incurred natural gas infrastructure replacement costs to be passed directly to customers. The return on equity to be used by Ameren Missouri for purposes of the ISRS tariff filing is 10%.

For additional information on Missouri rate matters, including Ameren Missouri’s 2012 electric rate order and the related court appeals, see Results of Operations and Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, Quantitative and Qualitative Disclosures About Market Risk under Part II, Item 7A, and Note 2 – Rate and Regulatory Matters, and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report.

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Ameren Illinois

Electric

About 99% of Ameren Illinois’ electric operating revenues were subject to regulation by the ICC in the year ended December 31, 2012, with the remainder subject to FERC regulation.

Under the Illinois Customer Choice Law, all electric customers in Illinois may choose their own electric energy provider. However, Ameren Illinois is required to serve as the provider of last resort (POLR) for electric customers within its territory who have not chosen an alternative retail electric supplier. Ameren Illinois’ obligation to provide POLR electric service varies by customer size. Ameren Illinois is not required to offer fixed-priced electric service to customers with electric demands of 400 kilowatts or greater, as the market for service to this group of customers has been declared competitive. Power and related procurement costs incurred by Ameren Illinois are passed directly to its customers through a cost recovery mechanism.

In 2012, Ameren Illinois elected to participate in the performance-based formula ratemaking process established pursuant to the IEIMA by filing initial performance-based formula rates with the ICC. The IEIMA was designed to provide for the recovery of actual costs of electric delivery service that are prudently incurred and to reflect the utility's actual regulated capital structure through the inclusion of a formula for calculating the return on equity component of the cost of capital. The return on equity component of the formula rate is equal to the average for the calendar year of the monthly yields of 30-year United States treasury bonds plus 590 basis points for 2012 and 580 basis points thereafter. Ameren Illinois' actual return on equity relating to electric delivery service will be subject to a collar adjustment on earnings in excess of 50 basis points above or below its allowed return. The IEIMA provides for an annual reconciliation of the revenue requirement necessary to reflect the actual costs incurred in a given year with the revenue requirement that was in effect for that year, including an allowed return on equity. This annual revenue reconciliation, along with the collar adjustment, if necessary, will be collected from or refunded to customers in a subsequent year.

Ameren Illinois is also subject to performance standards under the IEIMA. Failure to achieve the standards will result in a reduction in the company's allowed return on equity calculated under the formula. The performance standards include improvements in service reliability to reduce both the frequency and duration of outages, reduction in the number of estimated bills, reduction of consumption on inactive meters, and a reduction in uncollectible accounts expense. The IEIMA provides for return on equity penalties totaling up to 30 basis points in 2013 through 2015, 34 basis points in 2016 through 2018, and 38 basis points in 2019 through 2022 if the performance standards are not met. The formula ratemaking process is effective until the end of 2017, but could be extended by the Illinois General Assembly for an additional five years. The formula ratemaking

process would also terminate if the average residential rate increases by more than 2.5% annually from June 2011 through May 2014. The average residential rate includes generation service, which is outside of Ameren Illinois’ control, as Ameren Illinois is required to purchase all of its power through procurement processes administered by the IPA.

Between 2012 and 2021, Ameren Illinois is required, pursuant to the IEIMA, to invest $625 million in capital expenditures incremental to Ameren Illinois' average electric delivery capital expenditures for calendar years 2008 through 2010 to modernize its distribution system. Such investments are expected to encourage economic development and to create an estimated 450 additional jobs within Illinois. Ameren Illinois is subject to monetary penalties if 450 additional jobs are not created during the peak program year. Also, Ameren Illinois is required to contribute $1 million annually for certain nonrecoverable customer assistance programs and $1 million annually to the Illinois Science and Energy Innovation Trust for as long as Ameren Illinois participates in the formula ratemaking process. Ameren Illinois also was required to make a one-time $7.5 million nonrecoverable donation to the Illinois Science and Energy Innovation Trust in 2012.

Ameren Illinois' initial filing under IEIMA was based on 2010 recoverable costs and expected net plant additions for 2011 and 2012. In September 2012, the ICC issued an order approving an Ameren Illinois electric delivery service revenue requirement of $779 million, which was a $55 million decrease from the electric delivery service revenue requirement allowed in the pre-IEIMA 2010 electric delivery service rate order. The rates became effective on October 19, 2012, and were effective through the end of 2012. In October 2012, Ameren Illinois filed an appeal of the ICC order to the Appellate Court of the Fourth District of Illinois. A decision by the appellate court is expected in 2013. Ameren Illinois believes that the ICC has incorrectly implemented the IEIMA by using an average rate base as opposed to a year-end rate base in setting rates, through its treatment of accumulated deferred income taxes, and through the method it used for calculating the equity portion of Ameren Illinois' capital structure and the method for calculating interest on the revenue requirement reconciliation and return on equity collar. The ICC's September 2012 order jeopardizes Ameren Illinois' ongoing ability to implement infrastructure improvements to the extent and on the timetable envisioned in the IEIMA. Until the uncertainty surrounding how the Illinois law will ultimately be implemented is removed, Ameren Illinois is reducing its IEIMA capital spending with a corresponding negative effect on the job creation that the legislature sought to effectuate with the law. Although Ameren Illinois intends to meet its IEIMA capital spending requirements, it is proceeding on a slower investment schedule than previously contemplated.

In April 2012, Ameren Illinois submitted to the ICC an update filing under IEIMA based on 2011 recoverable costs and expected net plant additions for 2012. In December 2012, the ICC issued an order approving an Ameren Illinois electric delivery service revenue requirement of $764 million, which was a $15 million decrease in the revenue requirement allowed in the ICC

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initial filing order. The rates became effective on January 1, 2013, and will be effective through the end of 2013. Ameren Illinois will submit to the ICC during the second quarter of 2013 an update filing based on 2012 recoverable costs and expected net plant additions for 2013, which will determine rates that are effective during 2014.

In December 2012, the ICC approved Ameren Illinois' advanced metering infrastructure deployment plan, which outlines how Ameren Illinois will comply with the IEIMA requirement to spend $360 million on smart grid assets over ten years on a cost-beneficial basis to its electric customers. The plan targets the second quarter of 2014 to begin installation of smart meters.

Also, Ameren Illinois has approval from the ICC to use cost recovery mechanisms for energy efficiency programs, environmental costs and bad debt expense not recovered in base rates.

Ameren Illinois has a tariff rider to recover the costs of asbestos-related litigation claims, subject to the following terms: 90% of cash expenditures in excess of the amount included in base electric rates are to be recovered from a trust fund that was established when Ameren acquired IP. At December 31, 2012, the trust fund balance was $23 million, including accumulated interest. If cash expenditures are less than the amount in base rates, Ameren Illinois will contribute 90% of the difference to the fund. Once the trust fund is depleted, 90% of allowed cash expenditures in excess of base rates will be recovered through charges assessed to customers under the tariff rider. Following the Ameren Illinois Merger, this rider is applicable only for claims that occurred within IP’s historical service territory. Similarly, the rider will permit recovery only from customers within IP’s historical service territory.

As a member of MISO, Ameren Illinois' transmission rates are calculated in accordance with the MISO OATT. Ameren Illinois has received FERC approval to use company-specific, forward-looking rate formula templates in setting its transmission rates. These forward-looking rates are updated in January each year based on forecasted information, with an annual reconciliation to the actual revenue requirement based on the costs incurred. In Illinois, the AMIL pricing zone rate is charged directly to wholesale customers and alternative retail electric suppliers, which serve unbundled retail load. For Ameren Illinois retail customers who have not chosen an alternative retail electric supplier, the AMIL transmission rate, as well as other MISO-related costs, are collected through a rider mechanism in Ameren Illinois' retail distribution tariffs.

Natural Gas

All of Ameren Illinois’ natural gas operating revenues were subject to regulation by the ICC in the year ended December 31, 2012.

On January 25, 2013, Ameren Illinois filed a request with the ICC to increase its annual revenues for natural gas delivery service by $50 million. The request was based on a 10.4% return

on equity, a capital structure composed of 51.8% common equity, and a rate base of $1.1 billion. In an attempt to reduce regulatory lag, Ameren Illinois is using a future test year, 2014, in this proceeding. A decision by the ICC in this proceeding is required by December 2013. Ameren Illinois cannot predict the level of any delivery service rate changes the ICC may approve, when any rate changes may go into effect, or whether any rate changes that may eventually be approved will be sufficient to enable Ameren Illinois to recover its costs and earn a reasonable return on its investments when the rate changes go into effect.

If certain criteria are met, Ameren Illinois’ natural gas rates may be adjusted without a traditional rate proceeding. PGA clauses permit prudently incurred natural gas costs to be passed directly to the customer. Also, Ameren Illinois has approval from the ICC to use cost recovery mechanisms for energy efficiency programs, certain environmental costs and bad debt expense not recovered in base rates.

For additional information on Illinois rate matters, including the IEIMA and the Ameren Illinois' natural gas case filed in January 2013, see Results of Operations and Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, Quantitative and Qualitative Disclosures About Market Risk under Part II, Item 7A, and Note 2 – Rate and Regulatory Matters, and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report.

Merchant Generation

Merchant Generation revenues are determined by market conditions and contractual arrangements. We expect the Merchant Generation energy centers to have 5,522 megawatts of capacity available for the 2013 peak summer electrical demand. In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business's long-lived assets. As discussed below, Genco and AERG sell all of their power and capacity to Marketing Company through power supply agreements. Marketing Company attempts to optimize the value of those assets and to mitigate risks through a variety of techniques, including wholesale sales of capacity and energy, retail sales in the non-rate-regulated Illinois market, spot market sales primarily in MISO and PJM, and financial hedging transactions, including options and other derivatives. Marketing Company enters into long-term and short-term contracts. Marketing Company’s counterparties include cooperatives, municipalities, residential, commercial and industrial customers, power marketers, MISO, PJM and investor-owned utilities, including Ameren Illinois. Illinois law allows municipalities and counties to negotiate the purchase price of electricity on behalf of residential and small business utility customers. In 2012, Marketing Company began serving those Illinois municipalities electing to aggregate their residential and small commercial electric supply load, and which selected Marketing Company as their provider. For additional information on Marketing Company’s hedging activities, see Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under

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Part II, Item 7 and Note 7 – Derivative Financial Instruments under Part II, Item 8, of this report.

General Regulatory Matters

Ameren Missouri, Ameren Illinois, Genco, AERG and Marketing Company must receive FERC approval to enter into various transactions, including to issue short-term debt securities and to conduct certain acquisitions, mergers, and consolidations involving electric utility holding companies having a value in excess of $10 million. In addition, these Ameren utilities must receive authorization from the applicable state public utility regulatory agency to issue stock and long-term debt securities (with maturities of more than 12 months) and to conduct mergers, affiliate transactions, and various other activities.

Ameren Missouri, Ameren Illinois, Genco, AERG and ATXI are also subject to mandatory reliability standards, including cybersecurity standards, adopted by FERC to ensure the reliability of the bulk power electric system. These standards are developed and enforced by NERC pursuant to authority given to it by the FERC. If Ameren or its subsidiaries were found not to be in compliance with any of these mandatory reliability standards, they could incur substantial monetary penalties and other sanctions.

Under PUHCA 2005, FERC and any state public utility regulatory agencies may access books and records of Ameren and its subsidiaries that are determined to be relevant to costs incurred by Ameren’s rate-regulated subsidiaries with respect to jurisdictional rates. PUHCA 2005 also permits the MoPSC and the ICC to request that FERC review cost allocations by Ameren Services to other Ameren companies.

Operation of Ameren Missouri’s Callaway energy center is subject to regulation by the NRC. Its facility operating license expires on June 11, 2024. In December 2011, Ameren Missouri submitted a license extension application with the NRC to extend the energy center's operating license to 2044. There is no date by which the NRC must act on this relicensing request. Ameren Missouri’s Osage hydroelectric energy center and Ameren Missouri’s Taum Sauk pumped-storage hydroelectric energy center, as licensed projects under the Federal Power Act, are subject to FERC regulations affecting, among other things, the general operation and maintenance of the projects. The license for Ameren Missouri’s Osage hydroelectric energy center expires on March 30, 2047. In June 2008, Ameren Missouri filed a relicensing application with FERC to operate its Taum Sauk pumped-storage hydroelectric energy center for another 40 years. The existing FERC license expired on June 30, 2010. On July 2, 2010, Ameren Missouri received a license extension that allows Taum Sauk to continue operations until FERC issues a new license. FERC is reviewing the relicensing application. A FERC order is expected in 2013 or 2014. Ameren Missouri cannot predict the ultimate outcome of the order. Ameren Missouri’s Keokuk energy center and its dam in the Mississippi River between Hamilton, Illinois, and Keokuk, Iowa are operated under authority granted by an Act of Congress in 1905.

For additional information on regulatory matters, see Note 2

– Rate and Regulatory Matters, Note 10 - Callaway Energy Center, and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report, which include a discussion about the December 2005 breach of the upper reservoir at Ameren Missouri’s Taum Sauk pumped-storage hydroelectric energy center.

Environmental Matters

Certain of our operations are subject to federal, state, and local environmental statutes or regulations relating to the safety and health of personnel, the public, and the environment. These environmental statutes and regulations include requirements for identification, generation, storage, handling, transportation, disposal, recordkeeping, labeling, reporting, and emergency response in connection with hazardous and toxic materials; safety and health standards; and environmental protection requirements, including standards and limitations relating to the discharge of air and water pollutants, the protection of natural and cultural resources, and the management of waste and byproduct materials. Failure to comply with those statutes or regulations could have material adverse effects on us. We could be subject to criminal or civil penalties by regulatory agencies or we could be ordered by the courts to pay private parties. Except as indicated in this report, we believe that we are in material compliance with existing statutes and regulations.

In addition to existing laws and regulations, including the Illinois MPS that applies to AER's energy centers in Illinois, the EPA is developing environmental regulations that will have a significant impact on the electric utility industry. These regulations could be particularly burdensome for certain companies, including Ameren, Ameren Missouri, Genco, and AERG, that operate coal-fired energy centers. Significant new rules proposed or promulgated since the beginning of 2010 include the regulation of greenhouse gas emissions; revised national ambient air quality standards for SO₂ and NO₂ emissions; the CSAPR, which would have required further reductions of SO₂ emissions, NO_x emissions, and fine particulate matter emissions from energy centers; a regulation that governs management of CCR and coal ash impoundments; the MATS, which require reduction of emissions of mercury, toxic metals, and acid gases from energy centers; revised NSPS for particulate matter, SO₂, and NO_x emissions from new sources; and new regulations under the Clean Water Act that could require significant capital expenditures, such as for new water intake structures or cooling towers, at our energy centers. The EPA has proposed CO₂ limits for new coal-fired and natural gas-fired combined cycle units and is expected to propose limits for existing units in the future. These new and proposed regulations, if adopted, may be challenged through litigation, so their ultimate implementation as well as the timing of any such implementation is uncertain, as evidenced by the CSAPR being vacated and remanded back to the EPA by the United States Court of Appeals for the District of Columbia in August 2012. Although many details of these future regulations are unknown, the combined effects of the new and proposed environmental regulations may result in significant capital expenditures and/or increased operating costs over the next five to ten years for Ameren, Ameren Missouri and AER. Compliance

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with these environmental laws and regulations could be prohibitively expensive. If they are, these regulations could require us to close or to significantly alter the operation of our energy centers, which could have an adverse effect on our results of operations, financial position, and liquidity, including the impairment of long-lived assets. Failure to comply with environmental laws and regulations might also result in the imposition of fines, penalties, and injunctive measures.

The decision to make pollution control equipment investments at our Merchant Generation business depends on whether the expected future market price for power reflects the increased cost for environmental compliance. During early 2012, the observable market price for power for delivery in that year and in future years sharply declined below 2011 levels primarily because of declining natural gas prices, as well as the impact from the stay of the CSAPR. As a result of this sharp decline in the market price for power, as well as uncertain environmental regulations, Genco decelerated the construction of two scrubbers at its Newton energy center.

For additional discussion of environmental matters, including NOx, SO₂, and mercury emission reduction requirements, remediation efforts, and a discussion of the EPA’s allegations of violations of the Clean Air Act and Missouri law in connection with projects at Ameren Missouri's Rush Island energy center, and the EPA's Notice of Violation of permitting requirements at Genco's Newton energy center, see Liquidity and Capital Resources in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report.

TRANSMISSION AND SUPPLY OF ELECTRIC POWER

Ameren owns an integrated transmission system that comprises the transmission assets of Ameren Missouri, Ameren Illinois and ATXI. Ameren also operates two balancing authority areas, AMMO (which includes Ameren Missouri), and AMIL (which includes Ameren Illinois, ATXI, AERG, and Genco excluding EEI and Genco’s Elgin CT energy center). During 2012, the peak demand was 8,868 megawatts in AMMO and 9,720 megawatts in AMIL. The Ameren transmission system directly connects with 15 other balancing authority areas for the exchange of electric energy.

Ameren Missouri, Ameren Illinois and ATXI are transmission-owning members of MISO. Transmission service on the Ameren transmission system is provided pursuant to the terms of the MISO OATT on file with FERC. EEI operates its own balancing authority area and its own transmission facilities in southern Illinois. The EEI transmission system is directly connected to the transmission systems of MISO, the Tennessee Valley Authority, and Louisville Gas and Electric Company. EEI’s energy centers are dispatched separately from those of Ameren Missouri, Genco and AERG. Ameren Missouri is authorized by the MoPSC to participate in MISO, subject to certain conditions, through May 2016.

In May 2011 FERC approved transmission rate incentives for the Illinois Rivers project, which is being developed by ATXI. In December 2011, MISO approved the Illinois Rivers project as well as the Spoon River and Mark Twain projects. The total investment in these three MISO-approved projects is expected to be more than $1.3 billion from 2013 to 2019. These projects are located primarily in Illinois and Missouri.

In February 2012, FERC approved ATXI's request for a forward-looking rate calculation with an annual reconciliation adjustment, as well as ATXI's request for implementation of the incentives FERC approved in its May 2011 order for the Illinois Rivers project. In November 2012, FERC approved transmission rate incentives for the Spoon River project and the Mark Twain project. FERC also approved a forward-looking rate calculation with an annual reconciliation adjustment for Ameren Illinois' electric transmission business.

The Ameren Companies and EEI are members of SERC. SERC is responsible for the bulk electric power supply system in all or portions of Missouri, Illinois, Arkansas, Kentucky, Tennessee, North Carolina, South Carolina, Georgia, Mississippi, Alabama, Louisiana, Virginia, Florida, Oklahoma, Iowa, and Texas. As a result of the Energy Policy Act of 2005, owners and operators of the bulk electric power system are subject to mandatory reliability standards promulgated by NERC and its regional entities, such as SERC, which are enforced by FERC. The Ameren Companies must comply with these standards, which are in place to ensure the reliability of the bulk electric power system.

See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for additional information.

Ameren Missouri

Ameren Missouri’s electric supply is obtained primarily from its own generation. Factors that could cause Ameren Missouri to purchase power include, among other things, absence of sufficient owned generation, energy center outages, the fulfillment of renewable energy portfolio requirements, the failure of suppliers to meet their power supply obligations, extreme weather conditions, and the availability of power at a cost lower than the cost of generating it.

Ameren Missouri continues to evaluate its longer-term needs for new baseload and peaking electric generation capacity. The MoPSC's December 2012 electric rate order approved Ameren Missouri's implementation of MEEIA megawatthour savings targets, energy efficiency programs, and associated cost recovery mechanisms and incentive awards. The order allows for Ameren Missouri to collect its program costs and 90% of its projected lost revenue from customers over the same three-year period starting on January 2, 2013. The remaining 10% of projected lost revenue is expected to be recovered as part of future rate proceedings. The potential need for new generating plant construction is dependent on several key factors including: continuation of energy efficiency programs beyond 2015, load growth, customer participation in energy efficiency programs, and the potential for more stringent environmental regulation of coal-

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fired energy centers, which could lead to the retirement of current baseload assets. Because of the significant time required to plan, acquire permits for, and build a baseload power plant, Ameren Missouri continues to study future plant alternatives and is taking steps to preserve options to meet future demand. These steps include evaluating the potential for further energy efficiency programs in the long term, evaluating potential sites for natural gas-fired generation, and pursuing DOE funds through a partnership with Westinghouse for development of small modular reactor technology for nuclear power. Ameren Missouri's next Integrated Resource Plan filing with the MoPSC is due October 1, 2014.

See also Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, and Note 2 – Rate and Regulatory Matters and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report.

Ameren Illinois

Any electric supply purchased by Ameren Illinois for its retail customers comes either through an annual procurement process conducted by the IPA or through markets operated by MISO. The power and related procurement costs incurred by Ameren Illinois are passed directly to its customers through a cost recovery mechanism.

The IPA administers a RFP process that procures Ameren Illinois’ expected supply obligation. Since the RFP process began in 2009, the ICC has approved the outcomes of multiple electric power procurement RFPs for energy, capacity, and renewable energy credits covering different time periods.

A portion of the electric power supply required for Ameren Illinois to satisfy its distribution customers’ requirements is

purchased in the RFP process administered by the IPA from Marketing Company, on behalf of Genco and AERG, and from Ameren Missouri.

Under Illinois law, transmission and distribution service rates are regulated, while electric customers are allowed to purchase generation from an alternative retail electric supplier. At December 31, 2012, approximately 396,000 retail customers representing approximately 61% of Ameren Illinois' annual retail kilowatthour sales had elected to purchase their electricity from an alternative retail electric supplier. Customers who receive electricity from an alternative retail electric supplier continue to pay a delivery charge to Ameren Illinois for the distribution services they receive from Ameren Illinois.

See Note 2 – Rate and Regulatory Matters, Note 14 – Related Party Transactions and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report for additional information on power procurement in Illinois.

Merchant Generation

Genco and AERG have entered into power supply agreements with Marketing Company whereby Genco and AERG sell, and Marketing Company purchases, all of the capacity and energy available from Genco’s and AERG’s energy centers. These power supply agreements continue through December 31, 2022, and from year to year thereafter unless either party elects to terminate the agreement by providing the other party with no less than six months’ advance written notice. EEI and Marketing Company have entered into a power supply agreement for EEI to sell all of its capacity and energy to Marketing Company. This agreement expires on May 31, 2016. All of Genco’s, AERG’s and EEI’s energy centers compete for the sale of energy and capacity in the competitive energy markets through Marketing Company.

POWER GENERATION

The following table presents the source of electric generation, excluding purchased power, for the years ended December 31, 2012, 2011 and 2010:



	Coal		Nuclear		Natural Gas		Renewables^(a)		Oil
Ameren:^(b)
2012	81	%	15	%	3	%	1	%	(c)
2011	85		12		1		2		(c)
2010	85		12		1		2		(c)
Ameren Missouri:
2012	73	%	24	%	1	%	2	%	(c)
2011	77		19		1		3		(c)
2010	77		19		1		3		—
Merchant Generation:
2012	94	%	—		6	%	—		—
2011	98		—		2		—		(c)
2010	98		—		2		—		(c)


(a)	Renewable power generation includes production from Ameren Missouri's hydroelectric, pumped-storage, and methane gas energy centers, but excludes purchased renewable energy credits.


(b)	Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.


(c)	Less than 1% of total fuel supply.

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The following table presents the cost of fuels for electric generation for the years ended December 31, 2012, 2011, and 2010:



Cost of Fuels (Dollars per Mmbtu)	2012		2011		2010
Ameren:
Coal^(a)	$	2.081	$	1.931	$	1.848
Nuclear	0.964		0.750		0.701
Natural gas^(b)	3.772		6.097		6.539
Weighted average – all fuels^(c)	$	1.975	$	1.873	$	1.803
Ameren Missouri:
Coal^(a)	$	1.925	$	1.733	$	1.675
Nuclear	0.964		0.750		0.701
Natural gas^(b)	4.517		5.873		6.199
Weighted average – all fuels^(c)	$	1.743	$	1.610	$	1.563
Merchant Generation:
Coal^(a)	$	2.282	$	2.184	$	2.063
Natural gas^(b)	3.392		6.374		6.972
Weighted average – all fuels^(c)	$	2.359	$	2.292	$	2.169


(a)	The fuel cost for coal represents the cost of coal, the costs for transportation, which include railroad diesel fuel additives, and the cost of emission allowances.


(b)	The fuel cost for natural gas represents the cost of natural gas and firm and variable costs for transportation, storage, balancing, and fuel losses for delivery to the plant. In addition, the fixed costs for firm transportation and firm storage capacity are included in the calculation of fuel cost for the energy centers.


(c)	Represents all costs for fuels used in our energy centers, to the extent applicable, including coal, nuclear, natural gas, methane gas, oil, propane, tire chips, paint products, and handling. Oil, propane, tire chips, and paint products are not individually listed in this table because their use is minimal.

Coal

Ameren Missouri and the Merchant Generation business have agreements in place to purchase a portion of the coal they need and to transport it to energy centers through 2019. Ameren Missouri and Merchant Generation expect to enter into additional contracts to purchase coal from time to time. Coal supply agreements for Ameren Missouri have terms of up to six years, and expire between 2014 and 2017. Ameren Missouri has an ongoing need for coal to serve its native load customers, so it pursues a price hedging strategy consistent with this requirement. Merchant Generation's forward coal requirements and coal supply agreements are dependent on the volume of power sales contracted. Merchant Generation strives to achieve increased margin certainty by aligning its fuel purchases with its power sales. Ameren burned 34 million tons (Ameren Missouri – 19 million, Merchant Generation – 15 million) of coal in 2012. See Part II, Item 7A – Quantitative and Qualitative Disclosures About Market Risk of this report for additional information about coal supply contracts.

About 97% of Ameren’s coal (Ameren Missouri – 97%, Merchant Generation – 97%) is purchased from the Powder River Basin in Wyoming. The remaining coal is typically purchased from the Illinois Basin. Ameren Missouri and Merchant Generation have a goal to maintain coal inventory consistent with their risk management policies. Inventory may be adjusted because of changes in burn or uncertainties of supply due to potential work stoppages, delays in coal deliveries, equipment breakdowns, and other factors. In the past, deliveries from the Powder River Basin have occasionally been restricted because of rail maintenance, weather, and derailments. As of December 31, 2012, coal inventories for Ameren Missouri and for Merchant Generation were at or above targeted levels. Disruptions in coal deliveries could cause Ameren Missouri and Merchant Generation to pursue a strategy that could include reducing sales of power during low-margin periods, buying higher-cost fuels to

generate required electricity, and purchasing power from other sources.

Nuclear

The steps in the process to provide nuclear fuel generally involve the mining and milling of uranium ore to produce uranium concentrates, the conversion of uranium concentrates to uranium hexafluoride gas, the enrichment of that gas, and the fabrication of the enriched uranium hexafluoride gas into usable fuel assemblies. Ameren Missouri has entered into uranium, uranium conversion, uranium enrichment, and fabrication contracts to procure the fuel supply for its Callaway nuclear energy center.

Fuel assemblies for the 2013 spring refueling at Ameren Missouri's Callaway energy center were manufactured and were delivered to the energy center in January 2013. Ameren Missouri also has agreements or inventories to price-hedge approximately 99%, 52%, and 46% of Callaway's 2014, 2016 and 2017 refueling requirements, respectively. Ameren Missouri has uranium (concentrate and hexafluoride) inventories and supply contracts sufficient to meet all of its uranium and conversion requirements at least through 2017. Ameren Missouri has enriched uranium inventories and enrichment supply contracts sufficient to satisfy enrichment requirements through at least 2017. Fuel fabrication services are under contract through 2014. Ameren Missouri expects to enter into additional contracts to purchase nuclear fuel. As a member of Fuelco, Ameren Missouri can join with other member companies to increase its purchasing power, enhance diversification, and pursue opportunities for volume discounts. The Callaway energy center normally requires refueling at 18-month intervals. The last refueling was completed in November 2011. There is no refueling scheduled for 2015 and 2018. The nuclear fuel markets are competitive, and prices can be volatile; however, we do not anticipate any significant problems in meeting our future supply requirements.

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Natural Gas Supply for Generation

To maintain deliveries to natural gas-fired energy centers throughout the year, especially during the summer peak demand, Ameren’s portfolio of natural gas supply resources includes firm transportation capacity and firm no-notice storage capacity leased from interstate pipelines. Ameren Missouri and Merchant Generation primarily use the interstate pipeline systems of Panhandle Eastern Pipe Line Company, Trunkline Gas Company, Natural Gas Pipeline Company of America, and Mississippi River Transmission Corporation to transport natural gas to energy centers. In addition to physical transactions, Ameren uses financial instruments, including some in the NYMEX futures market and some in the OTC financial markets, to hedge the price paid for natural gas.

Ameren Missouri’s and Merchant Generation's natural gas procurement strategy is designed to ensure reliable and immediate delivery of natural gas to their energy centers. This is accomplished by optimizing transportation and storage options and minimizing cost and price risk through various supply and price-hedging agreements that allow access to multiple gas pools, supply basins, and storage services. As of December 31, 2012, Ameren Missouri had price-hedged about 34% and Merchant Generation had price hedged 59% of its expected natural gas supply requirements for generation in 2013.

Renewable Energy

Illinois and Missouri have enacted laws requiring electric utilities to include renewable energy resources in their portfolios. Illinois requires renewable energy resources to equal or exceed 2% of the total electricity that each electric utility supplies to its eligible retail customers as of June 1, 2008, with that percentage increasing to 10% by June 1, 2015, and to 25% by June 1, 2025. In 2012, Ameren Illinois procured approximately 8% of its total electricity from renewable energy resources. Ameren Illinois has procured renewable energy credits under the IPA-administered procurement process to meet the renewable energy portfolio requirement through at least May 2017. In December 2010, Ameren Illinois entered into 20-year agreements with renewable energy suppliers and commenced receiving renewable energy credits under these agreements in June 2012. Approximately 54% of the 2013 plan year renewable energy requirement will be met through these agreements. The remaining requirement will be met through IPA procurements, which resulted in contracts that were executed in February 2012 with a term of June 2013 through December 2017.

In Missouri, utilities are required to purchase or generate from renewable energy sources electricity equaling at least 2% of native load sales, with that percentage increasing to at least 15% by 2021, subject to a 1% annual limit on customer rate impacts. At least 2% of each renewable energy portfolio requirement must be derived from solar energy. Ameren Missouri expects to satisfy the nonsolar requirement through 2017 with its existing renewable generation, including the Maryland Heights energy center, along with a 15-year 102-megawatt power purchase agreement with a wind farm operator in Iowa that became

effective in 2009. Currently, Ameren Missouri expects to meet the solar energy requirement through the purchase of solar-generated renewable energy credits, and generation from solar panels installed on Ameren's general office building. However, Ameren Missouri is studying other options for compliance. In 2012, Ameren Missouri purchased or generated approximately 3% of its native load sales from renewable energy resources.

In 2012, Ameren Missouri began generating power at its Maryland Heights energy center. This energy center, located at a landfill in Maryland Heights, Missouri, has the capability to generate up to approximately 15 megawatts of electricity by burning methane gas collected from the landfill. Ameren Missouri signed a 20-year supply agreement with the landfill owner to purchase methane gas.

Energy Efficiency

Ameren’s rate-regulated utilities have implemented energy efficiency programs to educate and help their customers become more efficient users of energy. The MEEIA established a regulatory framework that, among other things, allows electric utilities to recover costs related to MoPSC-approved energy efficiency programs. The law requires the MoPSC to ensure that a utility’s financial incentives are aligned to help customers use energy more efficiently, to provide timely cost recovery, and to provide earnings opportunities associated with cost-effective energy efficiency programs. Missouri does not have a law mandating energy efficiency standards.

The MoPSC's December 2012 electric rate order approved Ameren Missouri's implementation of MEEIA megawatthour savings targets, energy efficiency programs, and associated cost recovery mechanisms and incentive awards. Beginning in 2013, Ameren Missouri will invest approximately $147 million over the next three years for energy efficiency programs. The order allows for Ameren Missouri to collect its program costs and 90% of its projected lost revenue from customers over the same three years starting on January 2, 2013. The remaining 10% of projected lost revenue is expected to be recovered as part of future rate proceedings.

Additionally, the order provides for an incentive award that would allow Ameren Missouri to earn additional revenues based on achievement of certain energy efficiency goals, including approximately $19 million if 100% of its energy efficiency goals are achieved during the three-year period, with the potential to earn more if Ameren Missouri's energy savings exceed those goals. Ameren Missouri must achieve at least 70% of its energy efficiency goals before it earns any incentive award. The recovery of the incentive award from customers, if the energy efficiency goals are achieved, would begin after the three-year energy efficiency plan is complete and upon the effective date of an electric service rate order or possibly with the future adoption of a rider mechanism. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for additional information.

Illinois has enacted a law requiring Ameren Illinois to offer energy efficiency programs. The law also allows recovery mechanisms of the programs’ costs. The ICC has issued orders

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approving Ameren Illinois’ electric and natural gas energy efficiency plans as well as cost recovery mechanisms by which program costs can be recovered from customers. In addition, over a ten-year period, Ameren Illinois will invest an estimated $625 million to upgrade and modernize its transmission and distribution infrastructure in accordance with the IEIMA. As part of these upgrades, Ameren Illinois expects to invest $360 million to install smart meters, which could enable customers to improve efficiency.

NATURAL GAS SUPPLY FOR DISTRIBUTION

Ameren Missouri and Ameren Illinois are responsible for the purchase and delivery of natural gas to their utility customers. Ameren Missouri and Ameren Illinois develop and manage a portfolio of natural gas supply resources. These include firm gas

supply under term agreements with producers, interstate and intrastate firm transportation capacity, firm storage capacity leased from interstate pipelines, and on-system storage facilities to maintain natural gas deliveries to customers throughout the year and especially during peak demand periods. Ameren Missouri and Ameren Illinois primarily use Panhandle Eastern Pipe Line Company, Trunkline Gas Company, Natural Gas Pipeline Company of America, Mississippi River Transmission Corporation, Northern Border Pipeline Company, and Texas Eastern Transmission Corporation interstate pipeline systems to transport natural gas to their systems. In addition to transactions requiring physical delivery, financial instruments, including those entered into in the NYMEX futures market and in the OTC financial markets, are used to hedge the price paid for natural gas. See Part II, Item 7A – Quantitative and Qualitative Disclosures About Market Risk of this report for additional information about natural gas supply contracts. Natural gas purchase costs are passed on to customers of Ameren Missouri and Ameren Illinois under PGA clauses, subject to prudency reviews by the MoPSC and the ICC. As of December 31, 2012, Ameren Missouri had price-hedged 89%, and Ameren Illinois had price-hedged 81%, of its expected natural gas supply requirements for distribution in 2013.

For additional information on our fuel and purchased power supply, see Results of Operations, Liquidity and Capital Resources and Effects of Inflation and Changing Prices in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report. Also see Quantitative and Qualitative Disclosures About Market Risk under Part II, Item 7A, of this report, Note 1 – Summary of Significant Accounting Policies, Note 7 – Derivative Financial Instruments, Note 10 – Callaway Energy Center, Note 14 – Related Party Transactions, and Note 15 – Commitments and Contingencies under Part II, Item 8 of this report.

INDUSTRY ISSUES

We are facing issues common to the electric and natural gas utility industry and the merchant electric generation industry. These issues include:


•	continually developing and complex environmental laws, regulations and issues, including air and water quality standards, mercury emissions standards, and likely greenhouse gas limitations and CCR management requirements;


•	political and regulatory resistance to higher rates;


•	the potential for changes in laws, regulations, and policies at the state and federal level;


•	access to, and uncertainty in, the capital and credit markets;


•	cybersecurity risk, including loss of operational control of energy centers and electric and natural gas transmission and distribution systems and/or loss of data, and compliance with related industry regulations;


•	the potential for more intense competition in generation, supply and distribution, including new technologies;


•	pressure on customer growth and usage in light of current economic conditions and energy efficiency initiatives;


•	the potential for reregulation in some states, which could cause electric distribution companies to build or acquire energy centers and to purchase less power from electric generation companies such as Genco and AERG;


•	changes in the structure of the industry as a result of changes in federal and state laws, including the formation and growth of independent transmission entities;


•	increases, decreases, and volatility in power prices due to the balance of supply and demand and marginal fuel costs;


•	weakened financial strength of merchant generators, especially those with coal-fired energy centers, including their ability to generate positive cash flows in competitive markets as they seek to comply with environmental regulations;


•	the availability of fuel and increases or decreases in fuel prices;


•	the availability of qualified labor and material, and rising costs;


•	regulatory lag;


•	the influence of macroeconomic factors, such as yields on United States treasury securities, on allowed rates of return on equity provided by regulators;


•	decreased or negative free cash flows due to rising infrastructure investments and regulatory frameworks;


•	public concern about the siting of new facilities;


•	aging infrastructure and the need to construct new power generation, transmission and distribution facilities, which have long time frames to completion, while at the same time, having little long-term visibility on power and commodity prices;


•	legislation or proposals for programs to encourage or mandate energy efficiency and renewable sources of power;


•	public concerns about nuclear generation and decommissioning and the disposal of nuclear waste; and


•	consolidation of electric and natural gas companies.

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We are monitoring these issues. Except as otherwise noted in this report, we are unable to predict what impact, if any, these issues will have on our results of operations, financial position, or liquidity. For additional information, see Risk Factors under Part I, Item 1A, and Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, and Note 2 – Rate and Regulatory Matters and Note 15 – Commitments and Contingencies under Part II, Item 8, of this report.

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OPERATING STATISTICS

The following tables present key electric and natural gas operating statistics for Ameren for the past three years:



Electric Operating Statistics – Year Ended December 31,	2012			2011			2010
Electric Sales – kilowatthours (in millions):
Ameren Missouri:
Residential	13,385			13,867			14,640
Commercial	14,575			14,743			15,002
Industrial	8,660			8,691			8,656
Other	126			127			129
Native load subtotal	36,746			37,428			38,427
Off-system and wholesale	7,293			10,715			9,796
Subtotal	44,039			48,143			48,223
Ameren Illinois:
Residential
Power supply and delivery service	9,507			11,771			12,340
Delivery service only	2,103			77			1
Commercial
Power supply and delivery service	2,985			3,662			4,419
Delivery service only	9,175			8,561			8,051
Industrial
Power supply and delivery service	1,595			1,502			1,389
Delivery service only	11,753			11,360			11,147
Other	523			529			545
Native load subtotal	37,641			37,462			37,892
Merchant Generation:
Nonaffiliate energy sales	25,552			31,148			30,788
Affiliate native energy sales	1,679			1,004			949
Subtotal	27,231			32,152			31,737
Eliminate affiliate sales	(1,679		)	(1,004		)	(949		)
Eliminate Ameren Illinois/Merchant Generation common customers	(7,261		)	(5,454		)	(5,016		)
Ameren total	99,971			111,299			111,887
Electric Operating Revenues (in millions):
Ameren Missouri:
Residential	$	1,297		$	1,272		$	1,193
Commercial	1,088			1,084			1,004
Industrial	435			438			399
Other	104			76			91
Native load subtotal	$	2,924		$	2,870		$	2,687
Off-system and wholesale	208			352			343
Subtotal	$	3,132		$	3,222		$	3,030
Ameren Illinois:
Residential
Power supply and delivery service	$	961		$	1,194		$	1,270
Delivery service only	90			3			—
Commercial
Power supply and delivery service	254			350			425
Delivery service only	177			157			143
Industrial
Power supply and delivery service	57			65			66
Delivery service only	46			43			38
Other	154			128			119
Native load subtotal	$	1,739		$	1,940		$	2,061
Merchant Generation:
Nonaffiliate energy sales	$	1,047		$	1,382		$	1,442
Affiliate native energy sales	311			232			231
Other	15			12			20
Subtotal	$	1,373		$	1,626		$	1,693
Eliminate affiliate revenues	(340		)	(258		)	(263		)
Ameren total	$	5,904		$	6,530		$	6,521

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Electric Operating Statistics – Year Ended December 31,	2012			2011			2010
Electric Generation – megawatthours (in millions):
Ameren Missouri	44.7			48.8			48.1
Merchant Generation:
Genco	18.5			22.0			22.0
AERG	7.2			7.0			7.5
Medina Valley	—			0.1			0.1
Subtotal	25.7			29.1			29.6
Ameren total	70.4			77.9			77.7
Price per ton of delivered coal (average)	$	36.63		$	33.79		$	32.91
Source of energy supply:
Coal	65.1		%	66.5		%	65.7		%
Nuclear	12.4			9.4			8.9
Hydroelectric	1.1			1.3			1.6
Natural gas	2.7			1.1			1.0
Purchased – Wind	0.4			0.3			0.3
Purchased – Other	18.3			21.4			22.5
	100.0		%	100.0		%	100.0		%



Gas Operating Statistics – Year Ended December 31,	2012			2011			2010
Natural Gas Sales (millions of dekatherms):
Ameren Missouri:
Residential	6			7			7
Commercial	3			3			4
Industrial	1			1			1
Subtotal	10			11			12
Ameren Illinois:
Residential	49			56			60
Commercial	17			21			23
Industrial	5			5			7
Other	3			—			—
Subtotal	74			82			90
Other:
Industrial	—			—			1
Subtotal	—			—			1
Ameren total	84			93			103
Natural Gas Operating Revenues (in millions)
Ameren Missouri:
Residential	$	85		$	96		$	100
Commercial	36			41			43
Industrial	8			9			10
Other	10			10			13
Subtotal	$	139		$	156		$	166
Ameren Illinois:
Residential	$	547		$	588		$	649
Commercial	172			195			223
Industrial	24			30			44
Other	43			33			37
Subtotal	$	786		$	846		$	953
Other:
Industrial	$	—		$	—		$	4
Eliminate affiliate revenues	(1		)	(1		)	(6		)
Ameren total	$	924		$	1,001		$	1,117
Peak day throughput (thousands of dekatherms):
Ameren Missouri	139			149			167
Ameren Illinois	1,061			1,157			1,227
Total peak day throughput	1,200			1,306			1,394

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AVAILABLE INFORMATION

The Ameren Companies make available free of charge through Ameren’s website (www.ameren.com) their annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, eXtensible Business Reporting Language (XBRL) documents, and any amendments to those reports filed with or furnished to pursuant to Sections 13(a) or 15(d) of the Exchange Act as soon as reasonably possible after such reports are electronically filed with, or furnished to, the SEC. These documents are also available through an Internet website maintained by the SEC (www.sec.gov). Ameren also uses its website as a channel of distribution of material information relating to the Ameren Companies. Financial and other material information regarding the Ameren Companies is routinely posted and accessible at Ameren’s website.

The Ameren Companies also make available free of charge through Ameren’s website the charters of Ameren’s board of directors’ audit and risk committee, human resources committee, nominating and corporate governance committee, finance committee, and nuclear oversight and environmental committee; the corporate governance guidelines; a policy regarding communications to the board of directors; a policy and procedures with respect to related-person transactions; a code of ethics for principal executive and senior financial officers; a code of business conduct applicable to all directors, officers and employees; and a director nomination policy that applies to the Ameren Companies. The information on Ameren’s website, or any other website referenced in this report, is not incorporated by reference into this report.


ITEM 1A.	RISK FACTORS

Investors should review carefully the following material risk factors and the other information contained in this report. The risks that the Ameren Companies face are not limited to those in this section. There may be further risks and uncertainties that are not presently known or that are not currently believed to be material that may adversely affect the results of operations, financial position, and liquidity of the Ameren Companies. See Forward-Looking Statements above and Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report.

The Ameren Companies are subject to extensive regulation of their businesses, which could adversely affect their results of operations, financial position, and liquidity.

The Ameren Companies are subject to, or affected by, extensive federal, state, and local regulation. This extensive regulatory framework, some but not all of which is more specifically identified in the following risk factors, regulates, among other matters, the electric and natural gas industries; rate and cost structure of utilities; operation of nuclear energy centers; construction and operation of generation, transmission, and distribution facilities; acquisition, disposal, depreciation and amortization of assets and facilities; transmission reliability; and

present or prospective wholesale and retail competition. The Ameren Companies must address in their business planning and management of operations the effects of existing and proposed laws and regulations and potential changes in the regulatory framework, including initiatives by federal and state legislatures, RTOs, utility regulators, and taxing authorities. Significant changes in the nature of the regulation of the Ameren Companies’ businesses could require changes to their business planning and management of their businesses and could adversely affect their results of operations, financial position, and liquidity. Failure of the Ameren Companies to obtain adequate rates or regulatory approvals in a timely manner, failure to obtain necessary licenses or permits from regulatory authorities, new or modified laws, regulations, standards, interpretations, or other legal requirements, or increased compliance costs could adversely impact the Ameren Companies’ results of operations, financial position, and liquidity.

The electric and natural gas rates that Ameren Missouri and Ameren Illinois are allowed to charge are determined through regulatory proceedings, which are subject to appeal, and are subject to legislative actions, which are largely outside of their control. Any events that prevent Ameren Missouri or Ameren Illinois from recovering their respective costs or from earning appropriate returns on their investments could adversely affect the Ameren Companies' results of operations, financial position, and liquidity.

The rates that Ameren Missouri and Ameren Illinois are allowed to charge for their utility services significantly influence the results of operations, financial position, and liquidity of these companies and Ameren. The electric and natural gas utility industries are highly regulated. The utility rates charged to Ameren Missouri and Ameren Illinois customers are determined, in large part, by governmental entities, including the MoPSC, the ICC, and FERC. Decisions by these entities are influenced by many factors, including the cost of providing service, the prudency of expenditures, the quality of service, regulatory staff knowledge and experience, economic conditions, public policy, and social and political views. Decisions made by these governmental entities regarding rates are largely outside of Ameren Missouri’s and Ameren Illinois’ control. Regulatory lag involved in filing and getting new rates approved could have a material adverse effect on our results of operations, financial position, and liquidity. Rate orders are also subject to appeal, which creates additional uncertainty as to the rates Ameren Missouri and Ameren Illinois will ultimately be allowed to charge for their services.

Ameren Missouri electric and natural gas utility rates and Ameren Illinois natural gas utility rates are typically established in regulatory proceedings that take up to 11 months to complete. Rates established in those proceedings for Ameren Missouri are primarily based on historical costs and revenues. Rates established in those proceedings for Ameren Illinois may be based on historical or estimated future costs and revenues. Thus, the rates a utility is allowed to charge may not match its costs at any given time. Rates include an allowed return on investments by the regulators. Although rate regulation is premised on

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providing a reasonable opportunity to earn a reasonable rate of return on invested capital, there can be no assurance that the applicable regulatory commission will judge all the costs of Ameren Missouri and Ameren Illinois to have been prudently incurred or that the regulatory process in which rates are determined will always result in rates that will produce full recovery of such costs or an adequate return on those investments.

In years when capital investments and operations costs rise while customer usage declines, such as in 2012, Ameren Missouri and Ameren Illinois may not be able to earn the allowed return established by their regulators. This could result in the deferral or elimination of planned capital investments, which reduces the rate base investments the utility operations earn a rate of return on. Additionally, a period of increasing rates for our customers could result in additional regulatory and legislative actions, as well as competitive and political pressures, which could adversely affect the Ameren Companies' results of operations, financial position, and liquidity.

Through its participation in the performance-based formula ratemaking process established pursuant to the IEIMA, Ameren Illinois’ return on equity will be directly correlated to yields on United States treasury bonds. Additionally, Ameren Illinois will be subject to an annual ICC prudence review and to the ICC's implementation of the IEIMA, and Ameren Illinois will be required to achieve performance objectives, increase capital spending levels, and meet job creation targets, which if not successfully completed or achieved could adversely affect Ameren Illinois' results of operations, financial position, and liquidity.

In 2012, Ameren Illinois elected to participate in the performance-based formula ratemaking process established pursuant to the IEIMA for its electric distribution business. The ICC will annually review Ameren Illinois’ performance-based rate filings under the IEIMA for reasonableness and prudency. If the ICC were to conclude that Ameren Illinois’ incurred costs were not prudently incurred, the ICC could disallow recovery of such costs. Ameren is also subject to the ICC's implementation of the IEIMA's formula rates. After reviewing the ICC's IEIMA formula rate orders in 2012, Ameren Illinois believes that the ICC has incorrectly implemented the IEIMA. Ameren Illinois objects to the ICC's use of an average rate base as opposed to a year-end rate base in setting rates, to its treatment of accumulated deferred income taxes, and to the methods it used to calculate the equity portion of Ameren Illinois' capital structure and to calculate interest on the revenue requirement reconciliation and return on equity collar.

The return on equity component of the formula rate is equal to the average for the calendar year of the monthly yields of 30-year United States treasury bonds plus 580 basis points for years after 2012. Therefore, Ameren Illinois’ annual return on equity will be directly correlated to yields on United States treasury bonds, which are outside of Ameren Illinois’ control.

Ameren Illinois will also be subject to performance

standards. Failure to achieve the standards will result in a reduction in the company’s allowed return on equity calculated under the formula. The IEIMA provides for return on equity penalties totaling 30 basis points in 2013 through 2015, 34 basis points in 2016 through 2018, and 38 basis points in 2019 through 2022 if the performance standards are not met.

Between 2012 and 2021, Ameren Illinois will be required to invest $625 million in capital expenditures incremental to Ameren Illinois’ average electric delivery capital expenditures for calendar years 2008 through 2010 to modernize its distribution system. Ameren Illinois is subject to monetary penalties if 450 additional jobs in Illinois are not created during the peak program year.

The formula ratemaking process would terminate if the average residential rate increases by more than 2.5% annually from June 2011 through May 2014. The average residential rate includes generation service, which is outside of Ameren Illinois’ control, as Ameren Illinois is required to purchase all of its power through procurement processes administered by the IPA. If the performance-based formula rate process is terminated, Ameren Illinois would be required to establish future rates through a traditional rate proceeding with the ICC, which might not result in rates that produce a full or timely recovery of costs or an adequate return on investments. Unless extended, the IEIMA formula ratemaking process expires in 2017.

Energy conservation, energy efficiency efforts and other factors that reduce energy demand could adversely affect the Ameren Companies’ results of operations, financial position, and liquidity.

Regulatory and legislative bodies have proposed or introduced requirements and incentives to reduce energy consumption. Conservation and energy efficiency programs are designed to reduce energy demand. Unless there is a regulatory solution ensuring recovery, declining usage will result in an underrecovery of fixed costs at our rate-regulated business. Ameren Missouri, even with the implementation of energy efficiency programs under the MEEIA, is exposed to declining usage losses from energy efficiency efforts not related to its specific programs as well as distributed generation sources such as solar panels. Macroeconomic factors resulting in low economic growth or contraction within the Ameren Companies' service territories could also reduce energy demand.

We are subject to various environmental laws and regulations that require significant capital expenditures. Failure to meet these standards could result in closure of facilities, increase our operating costs, adversely affect our results of operations, financial position, and liquidity, or expose us to fines and liabilities.

We are subject to various environmental laws and regulations enforced by federal, state, and local authorities. From the beginning phases of siting and development to the operation of existing or new electric generating, transmission and distribution facilities and natural gas storage, transmission and distribution facilities, our activities involve compliance with diverse environmental laws and regulations. These laws and

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regulations address emissions, impacts to air, land, and water, noise, protected natural and cultural resources (such as wetlands, endangered species, and other protected wildlife, and archaeological and historical resources), and chemical and waste handling. Complex and lengthy processes are required to obtain approvals, permits, or licenses for new, existing, or modified facilities. Additionally, the use and handling of various chemicals or hazardous materials (including wastes) requires release prevention plans and emergency response procedures.

We are also subject to liability under environmental laws that address the remediation of environmental contamination of property now or formerly owned by us or by our predecessors, as well as property contaminated by hazardous substances that we generated. Such sites include MGP sites and third-party sites, such as landfills. Additionally, private individuals may seek to enforce environmental laws and regulations against us and could allege injury from exposure to hazardous materials.

In addition to existing laws and regulations, including the Illinois MPS that applies to our energy centers in Illinois, the EPA is developing numerous new environmental regulations that will have a significant impact on the electric utility industry. These regulations could be particularly burdensome for certain companies, including Ameren, Ameren Missouri, and AER, that operate coal-fired energy centers. These new regulations may be litigated, so the timing of their ultimate implementation is uncertain, as evidenced by the stay and remand of the CSAPR.

Ameren is also subject to risks in connection with changing or conflicting interpretations of existing laws and regulations. The EPA is engaged in an enforcement initiative to determine whether coal-fired energy centers failed to comply with the requirements of the NSR and NSPS provisions under the Clean Air Act when the energy centers implemented modifications. Following the issuance of a Notice of Violation, in January 2011, the Department of Justice on behalf of the EPA filed a complaint against Ameren Missouri in the United States District Court for the Eastern District of Missouri. The EPA’s complaint alleges that in performing projects at its Rush Island coal-fired energy center, Ameren Missouri violated provisions of the Clean Air Act and Missouri law. In January 2012, the United States District Court granted, in part, Ameren Missouri’s motion to dismiss various aspects of the EPA’s penalty claims. The EPA’s claims for injunctive relief, including requiring the installation of pollution control equipment, remain. Litigation of this matter could take many years. An outcome in this matter adverse to Ameren Missouri could require substantial capital expenditures and the payment of substantial penalties, neither of which can be determined at this time. Such expenditures could affect unit retirement and replacement decisions.

In August 2012, Genco received a Notice of Violation from the EPA alleging violations of permitting requirements including Title V of the Clean Air Act. The EPA contends that projects performed in 1997, 2006, and 2007 at Genco's Newton energy center violated federal laws. Ameren and Genco are unable to predict the outcome of this matter and whether the EPA will address this Notice of Violation administratively or through

litigation.

Ameren, Ameren Missouri, and AER have incurred and expect to incur significant costs related to environmental compliance and site remediation. New environmental regulations, revised environmental regulations, voluntary compliance guidelines, enforcement initiatives, or legislation could result in a significant increase in capital expenditures and operating costs, decreased revenues, increased financing requirements, penalties, fines, or closure of facilities for Ameren, Ameren Missouri, and AER. Actions required to ensure that our facilities and operations are in compliance with environmental laws and regulations could be prohibitively expensive. As a result, environmental regulations could require us to close or to significantly alter the operation of our energy centers, which could have an adverse effect on our results of operations, financial position, and liquidity, including the impairment of plant assets. Although costs incurred by Ameren Missouri ensure that its facilities are in compliance with environmental laws and regulations would be eligible for recovery in rates over time, subject to MoPSC approval in a rate proceeding, there is no similar cost recovery mechanism with respect to AER. We are unable to predict the ultimate impact of these matters on our results of operations, financial position, and liquidity.

Future limits on greenhouse gas emissions would probably require Ameren, Ameren Missouri, and AER to incur significant increases in capital expenditures and operating costs, which, if excessive, could result in the closures of coal-fired energy centers, impairment of assets, or otherwise adversely affect our results of operations, financial position, and liquidity.

State and federal authorities, including the United States Congress, have considered initiatives to limit greenhouse gas emissions and to address global climate change. Impacts from any climate change legislation or regulation could vary, depending upon proposed CO2 emission limits, the timing of implementation of those limits, the method of distributing any allowances, the degree to which offsets are allowed and available, and provisions for cost-containment measures, such as a “safety valve” provision that provides a maximum price for emission allowances. As a result of our diverse fuel portfolio, our emissions of greenhouse gases vary among our energy centers, but coal-fired energy centers are significant sources of CO2. The enactment of a climate change law could result in a significant rise in rates for electricity, and thereby household costs. The burden could fall particularly hard on electricity consumers and upon the economy in the Midwest because of the region’s reliance on electricity generated by coal-fired energy centers.

Future federal and state legislation or regulations that mandate limits on the emission of greenhouse gases would probably result in significant increases in capital expenditures and operating costs, which, in turn, could lead to increased liquidity needs and higher financing costs. Moreover, if Ameren Missouri requests recovery of these costs through rates, its regulators could deny some or all of these costs, or defer timely recovery of them. Excessive costs to comply with future

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legislation or regulations might force Ameren, Ameren Missouri, and AER to close some coal-fired energy centers earlier than planned, which could lead to possible impairment of assets and reduced revenues. As a result, mandatory limits could have a material adverse impact on Ameren’s, Ameren Missouri’s, and AER's results of operations, financial position, and liquidity.

The construction of, and capital improvements to, the Ameren Companies' electric and natural gas utility infrastructure and AER's energy centers involve substantial risks. These risks include escalating costs, unsatisfactory performance by the projects when completed, the inability to complete projects as scheduled, cost disallowances by regulators, and the inability to earn a reasonable return on invested capital, any of which could result in higher costs and the closure of facilities.

The Ameren Companies expect to incur significant capital expenditures to comply with existing and known environmental regulations and to make investments in their electric and natural gas utility infrastructure and in AER's energy centers if they are owned by Ameren over the next five years. Ameren estimates it will incur up to $9.5 billion (Ameren Missouri - up to $3.8 billion; Ameren Illinois - up to $3.9 billion; AER - up to $0.4 billion; other - up to $1.4 billion) of capital expenditures during the period 2013 through 2017. These expenses include construction expenditures, capitalized interest or allowance for funds used during construction, and capital expenditures for compliance with environmental standards and with the requirements of the IEIMA.

Investments in Ameren’s rate-regulated operations are expected to be recoverable from ratepayers, but are subject to prudency reviews and regulatory lag. The recoverability of amounts expended in Ameren's Merchant Generation operations will depend upon market prices for capacity and energy.

The ability of the Ameren Companies to complete construction projects successfully, and within projected estimates, is contingent upon many variables and subject to substantial risks. These variables include, but are not limited to, project management expertise and escalating costs for materials, labor, and environmental compliance. Delays in obtaining permits, shortages in materials and qualified labor, suppliers and contractors who do not perform as required under their contracts, changes in the scope and timing of projects, the inability to raise capital on favorable terms, or other events beyond our control that could occur may materially affect the schedule, cost, and performance of these projects. With respect to capital expenditures for pollution control equipment, there is a risk that energy centers will not be permitted to continue to operate if pollution control equipment is not installed by prescribed deadlines or does not perform as expected. Should any such pollution control equipment not be installed on time or perform as expected, the Ameren Companies could be subject to additional costs and to the loss of their investment in the project or facility. All of these risks may adversely affect the Ameren Companies’ results of operations, financial position, and liquidity.

As of December 31, 2012, Ameren Missouri had capitalized $69 million of costs incurred to license additional nuclear generation at its Callaway energy site. If efforts are permanently abandoned or management concludes it is probable the costs incurred will be disallowed in rates, a charge to earnings would be recognized in the period in which that determination was made.

We may not be able to execute our electric transmission investment plans and realize the expected return on those investments.

Ameren, through ATXI and Ameren Illinois, is allocating significant additional capital resources to electric transmission investments. This allocation of capital resources is based on FERC's regulatory framework and a rate of return on common equity that is currently higher than allowed by our state commissions. However the FERC regulatory framework and rate of return is subject to change and the regulatory framework may not be as favorable, or the rate of return may be lower, in the future. A significant number of our planned electric transmission investments have been approved by MISO as three separate multi-value projects to be constructed by ATXI. The total investment in these three projects is expected to be more than $1.3 billion with the last of these projects expected to be completed in 2019. Any failure by Ameren to complete these three projects as designed on time and within projected cost estimates, could adversely affect our results of operations, financial position, and liquidity. Future investments may be affected by changes in FERC policy regarding the utilities' right of first refusal to construct new transmission projects within their service territory. In the future, Ameren may not be able to invest in electric transmission to the extent desired.

Our counterparties may not meet their obligations to us, and Ameren affiliates may not meet their obligations to each other.

We are exposed to the risk that counterparties to various arrangements who owe us money, credit, energy, coal, or other commodities or services will not be able to perform their obligations or, with respect to our credit facilities, will fail to honor their commitments. Should the counterparties to commodity arrangements fail to perform, we might be forced to replace or to sell the underlying commitment at then-current market prices. Should the lenders under our credit facilities fail to perform, the level of borrowing capacity under those arrangements would decrease, unless we were able to find replacement lenders to assume the nonperforming lender’s commitment. In such an event, we might incur losses, or our results of operations, financial position, and liquidity could otherwise be adversely affected.

Certain of the Ameren Companies have obligations to other Ameren Companies or other Ameren subsidiaries as a result of transactions involving energy, coal, other commodities and services, borrowing from the money pools, and as a result of hedging transactions. If one Ameren entity failed to perform under any of these arrangements, other Ameren entities might incur

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losses. Their results of operations, financial position, and liquidity could be adversely affected, resulting in the nondefaulting Ameren entity being unable to meet its obligations, including to unrelated third parties. Ameren (parent) may itself have to fulfill its subsidiary obligations based on guarantees it has entered into on behalf of its subsidiaries. See Note 14 - Related Party Transactions under Part II, Item 8 for information on Ameren (parent) guarantees.

Increasing costs associated with our defined benefit retirement and postretirement plans, health care plans, and other employee benefits could adversely affect our results of operations, financial position, and liquidity.

We offer defined benefit retirement and postretirement plans that cover substantially all of our employees. Assumptions related to future costs, returns on investments, interest rates, and other actuarial matters have a significant impact on our earnings and funding requirements. Ameren expects to fund its pension plans at a level equal to the greater of the pension expense or the legally required minimum contribution. Considering Ameren’s assumptions at December 31, 2012, its investment performance in 2012, and its pension funding policy, Ameren expects to make annual contributions of $60 million to $150 million in each of the next five years, with aggregate estimated contributions of $550 million. We expect Ameren Missouri’s and Ameren Illinois’ portion of the future funding requirements to be 50% and 40%, respectively. These amounts are estimates. They may change with actual investment performance, changes in interest rates, changes in our assumptions, changes in government regulations, and any voluntary contributions.

In addition to the costs of our retirement plans, the costs of providing health care benefits to our employees and retirees have increased in recent years. We believe that our employee benefit costs, including costs of health care plans for our employees and former employees, will continue to rise. The increasing costs and funding requirements associated with our defined benefit retirement plans, health care plans, and other employee benefits could increase our financing needs and otherwise materially adversely affect our results of operations, financial position, and liquidity.

Our electric generation, transmission and distribution facilities are subject to operational risks that could adversely affect our results of operations, financial position, and liquidity.

The Ameren Companies’ financial performance depends on the successful operation of electric generation, transmission, and distribution facilities. Operation of electric generation, transmission, and distribution facilities involves many risks, including:


•	facility shutdowns due to operator error or a failure of equipment or processes;


•	longer-than-anticipated maintenance outages;


•	older generating equipment may require significant expenditures to keep it operating at peak efficiency;


•	disruptions in the delivery of fuel or lack of adequate

inventories, including ultra-low-sulfur coal used for Ameren Missouri’s compliance with environmental regulations;


•	lack of water, through low river levels or other causes, required for cooling plant operations;


•	labor disputes;


•	inability to comply with regulatory or permit requirements, including those relating to environmental contamination;


•	disruptions in the delivery of electricity, including impacts on us or our customers;


•	handling and storage of fossil-fuel combustion byproducts, such as CCR;


•	unusual or adverse weather conditions, including severe storms, droughts, floods and tornadoes;


•	a workplace accident that might result in injury or loss of life, extensive property damage, or environmental damage;


•	cybersecurity risk, including loss of operational control of our energy centers and our electric and natural gas transmission and distribution systems and/or loss of data, such as utility customer data, account information, and intellectual property through insider or outsider actions;


•	catastrophic events such as fires, explosions, pandemic health events, or other similar occurrences;


•	limitations on amounts of insurance available to cover losses that might arise in connection with operating our electric generation, transmission, and distribution facilities; and


•	other unanticipated operations and maintenance expenses and liabilities.

Our natural gas distribution and storage activities involve numerous risks that may result in accidents and other operating risks and costs that could adversely affect our results of operations, financial position, and liquidity.

Inherent in our natural gas distribution and storage activities are a variety of hazards and operating risks, such as leaks, accidental explosions, mechanical problems and cybersecurity risks, which could cause substantial financial losses. In addition, these risks could result in serious injury to employees and nonemployees, loss of human life, significant damage to property, environmental pollution, and impairment of our operations, which in turn could lead to substantial losses for us. In accordance with customary industry practice, we maintain insurance against some, but not all, of these risks and losses. The location of distribution lines and storage facilities near populated areas, including residential areas, commercial business centers, industrial sites, and other public gathering places, could increase the level of damages resulting from these risks. The occurrence of any of these events not fully covered by insurance could materially adversely affect our results of operations, financial position, and liquidity.

We are subject to federal regulatory compliance and proceedings, which increase our risk of regulatory penalties and other sanctions.

The Energy Policy Act of 2005 increased FERC’s civil penalty authority for violation of FERC statutes, rules, and orders, including FERC Reliability Standards. FERC can impose

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penalties of $1 million per violation per day. Under the Energy Policy Act of 2005, the Ameren Companies, as owners and operators of bulk power transmission systems and/or electric energy centers, are subject to mandatory NERC reliability standards, including cybersecurity standards. Compliance with these mandatory reliability standards may subject the Ameren Companies to higher operating costs and may result in increased capital expenditures. If the Ameren Companies were found not to be in compliance with these mandatory reliability standards or other FERC statutes, rules and orders, the Ameren Companies could incur substantial monetary penalties and other sanctions, which could adversely affect our results of operations, financial position, and liquidity. FERC also conducts audits and reviews of Ameren Missouri's, Ameren Illinois', and ATXI's accounting records to assess the accuracy of its formula rate-making process and has the ability to require retroactive refunds to customers for previously billed amounts, with interest.

Even though agreements have been reached with the state of Missouri and the FERC, the breach of the upper reservoir of Ameren Missouri’s Taum Sauk pumped-storage hydroelectric energy center could continue to have a material adverse effect on Ameren’s and Ameren Missouri’s results of operations, liquidity, and financial condition.

In December 2005, there was a breach of the upper reservoir at Ameren Missouri’s Taum Sauk pumped-storage hydroelectric energy center. This resulted in significant flooding in the local area, which damaged a state park. Ameren Missouri has settled with FERC and the state of Missouri all issues associated with the December 2005 Taum Sauk incident.

Ameren Missouri had liability insurance coverage for the Taum Sauk incident, subject to certain limits and deductibles. Currently, Ameren Missouri has filed separate lawsuits against two different liability insurance providers claiming that the insurance companies breached their duty to indemnify Ameren Missouri for the losses experienced from the incident. Ameren’s and Ameren Missouri’s results of operations, financial position, and liquidity could be adversely affected if Ameren Missouri’s remaining liability insurance claims of $68 million as of December 31, 2012, are not paid by insurers.

Ameren's Merchant Generation energy centers must compete for the sale of energy and capacity, which exposes that business to price risks.

All of Ameren's Merchant Generation energy centers compete for the sale of energy and capacity in the competitive energy markets.

To the extent that electricity generated by these energy centers is not under a fixed-price contract to be sold, the revenues and results of operations of these Merchant Generation subsidiaries generally depend on the prices that can be obtained for energy and capacity in Illinois and adjacent markets by Marketing Company.

Market prices for energy and capacity may fluctuate substantially over both the short and long term. For example,

market prices for power have decreased over the past several years. Demand for electricity and fuel can fluctuate dramatically, creating periods of substantial undersupply or oversupply. During periods of oversupply, prices might be depressed. Also, at times legislators or regulators with jurisdiction over wholesale and retail energy commodity and transportation rates may impose price limitations, bidding rules, and other mechanisms to address volatility and other issues in these markets.

For power products sold in advance, contract prices are influenced both by market conditions and by contract terms such as damage provisions, credit support requirements, and the number of available counterparties interested in contracting for the desired forward period. Depending on differences between market factors at the time of contracting versus current conditions, Marketing Company’s contract portfolio may have average contract prices greater than or less than current market prices, including at the expiration of the contracts, which could affect Ameren’s results of operations, financial condition and liquidity.

Any unhedged forecasted generation will be exposed to market prices at the time of sale. As a result, any new physical or financial power sales may be at price levels lower than previously experienced and lower than the value of existing hedged sales.

Among the factors that could influence such prices (all of which are beyond our control to a significant degree) are:


•	current and future delivered market prices for natural gas, coal, and related transportation costs;


•	current and forward prices for the sale of electricity;


•	current and future prices for emission allowances that may be required to operate the fossil-fuel-fired electric energy centers in compliance with environmental laws and permits;


•	the extent of additional supplies of electric energy from current competitors or new market entrants;


•	the regulatory and market structures developed for evolving Midwest energy markets, including a capacity market in MISO;


•	changes enacted by the Illinois legislature, the ICC, the IPA, or other government agencies with respect to power procurement procedures;


•	the potential for reregulation of generation in some states;


•	future pricing for, and availability of, services on transmission systems, and the effect of RTOs and export energy transmission constraints, which could limit our ability to sell energy in our markets;


•	the growth rate or decline in electricity usage as a result of population changes, regional economic conditions, and the implementation of energy-efficiency and conservation programs;


•	climate conditions in the Midwest market and major natural disasters; and


•	environmental laws and regulations or delays in their effective dates.

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There is substantial uncertainty concerning the manner, timing, and terms of our anticipated exit from the Merchant Generation business.

In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business's long-lived assets. However, Ameren's date and method of exit from the Merchant Generation business are currently uncertain. Exit strategies may include the sale of all or parts of Ameren's Merchant Generation business and the restructuring of all or a portion of Ameren's equity position in Genco. Once a plan of disposal is finalized, Ameren's implementation of that plan may result in long-lived asset impairments, disposal-related losses, contingencies, reduction of existing deferred tax assets, and other consequences that are currently unknown to Ameren.

Ameren's Merchant Generation business is experiencing a period of declining operating revenues and higher costs with limited available sources of external liquidity, and internal sources of liquidity available only at Ameren's discretion, which could be withheld by Ameren. Merchant Generation, including Genco, may require liquidity support from Ameren, which could adversely affect Ameren's results of operations, financial position, and liquidity.

Based on projections as of December 31, 2012, of its operating results and cash flows, Genco expects that, by the end of the first quarter of 2013, its interest coverage ratio will be less than the minimum ratio required for the company to borrow additional funds from external, third-party sources. Genco's indenture does not restrict intercompany borrowings from Ameren's non-state-regulated subsidiary money pool. However, borrowings from the money pool are subject to Ameren's control. If a Genco intercompany financing need were to arise, borrowings from the non-state-regulated subsidiary money pool by Genco would be dependent on consideration by Ameren of the facts and circumstances existing at that time. It is probable that during 2013 Genco will seek mid-month liquidity from Ameren to support the timing of Genco's cash flows. Ameren may decide not to provide funding to Genco should a financing need arise in 2013 or in the future. Genco also has significant debt maturities beginning in 2018. If Genco is unable to meet its liquidity needs, this could result in Genco accelerating asset sales, or restructuring. Genco expects to sell certain of its long-lived assets, either individually or through its put option with AERG, but the proceeds realized from any asset sale may not be adequate to satisfy Genco's liquidity needs.

Ameren's December 2012 decision that the Merchant Generation segment is no longer a core component of its future strategy could adversely affect Ameren's results of operations, financial position, and liquidity. Ameren has begun planning to reduce, and ultimately to eliminate, the reliance of the Merchant Generation segment, including Genco, on Ameren's financial support and shared service support. Ameren's exit date from the Merchant Generation segment is uncertain. By requiring the

Merchant Generation segment to duplicate support services, Ameren may reduce the synergies between its business segments. Further, counterparties may not extend credit to the Merchant Generation segment, which could limit Merchant Generation revenue opportunities and may result in a need for additional liquidity to operate the business. Also, Ameren has supplied guarantees to support Marketing Company's creditworthiness with counterparties. Under these guarantees, Ameren may have to fulfill Marketing Company obligations if Marketing Company becomes unable to satisfy the counterparty obligation with its own liquidity. Ameren may also be required to supply liquidity and to contribute capital to AERG should Genco exercise its put option agreement relating to three natural-gas-fired energy centers. See Note 14 - Related Party Transactions under Part II, Item 8, of this report for additional information about the put option agreement and Ameren parent guarantees.

Ameren Missouri’s ownership and operation of a nuclear energy center creates business, financial, and waste disposal risks.

Ameren Missouri’s ownership of the Callaway energy center subjects it to the risks of nuclear generation, which include the following:


•	potential harmful effects on the environment and human health resulting from the operation of nuclear facilities and the storage, handling, and disposal of radioactive materials;


•	the lack of a permanent waste storage site;


•	limitations on the amounts and types of insurance commercially available to cover losses that might arise in connection with the Callaway energy center or other United States nuclear operations;


•	uncertainties with respect to contingencies and retrospective premium assessments relating to claims at the Callaway energy center or any other United States nuclear energy center;


•	public and governmental concerns over the adequacy of security at nuclear energy centers;


•	uncertainties with respect to the technological and financial aspects of decommissioning nuclear energy centers at the end of their licensed lives (Ameren Missouri has submitted an application with the NRC to extend the Callaway energy center’s operating license from 2024 to 2044);


•	limited availability of fuel supply; and


•	costly and extended outages for scheduled or unscheduled maintenance and refueling.

The NRC has broad authority under federal law to impose licensing and safety requirements for nuclear energy centers. In the event of noncompliance, the NRC has the authority to impose fines or to shut down a unit, or both, depending upon its assessment of the severity of the situation, until compliance is achieved. Revised safety requirements promulgated from time to time by the NRC could necessitate substantial capital expenditures at nuclear energy centers such as Ameren Missouri’s. In addition, if a serious nuclear incident were to occur, it could have a material but indeterminable adverse effect on Ameren Missouri’s results of operations, financial condition, and

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liquidity. A major incident at a nuclear energy center anywhere in the world could cause the NRC to limit or prohibit the operation or relicensing of any domestic nuclear unit. An incident at a nuclear energy center anywhere in the world also could cause the NRC to impose additional conditions or requirements on the industry, which could increase costs and result in additional capital expenditures. For example, the earthquake in 2011 that affected nuclear energy centers in Japan has resulted in regulatory changes in the United States, and may result in future regulatory changes, that may impose additional costs on all United States nuclear energy centers.

Our energy risk management strategies may not be effective in managing fuel and electricity procurement and pricing risks, which could result in unanticipated liabilities or increased volatility in our earnings and cash flows.

We are exposed to changes in market prices for natural gas, fuel, power, emission allowances, renewable energy credits, and transmission congestion. Prices for natural gas, fuel, power, emission allowances and renewable energy credits may fluctuate substantially over relatively short periods of time, and at other times exhibit sustained increases or decreases, and expose us to commodity price risk. We use short-term and long-term purchase and sales contracts in addition to derivatives such as forward contracts, futures contracts, options, and swaps to manage these risks. We attempt to manage our risk associated with these activities through enforcement of established risk limits and risk management procedures. We cannot ensure that these strategies will be successful in managing our pricing risk or that they will not result in net liabilities because of future volatility in these markets.

Although we routinely enter into contracts to hedge our exposure to the risks of demand and changes in commodity prices, we do not hedge the entire exposure of our operations from commodity price volatility. Furthermore, our ability to hedge our exposure to commodity price volatility depends on liquid commodity markets. To the extent that commodity markets are illiquid, we may not be able to execute our risk management strategies, which could result in greater unhedged positions than we would prefer at a given time. To the extent that unhedged positions exist, fluctuating commodity prices can adversely affect our results of operations, financial position, and liquidity.

Our facilities are considered critical energy infrastructure and may therefore be targets of acts of terrorism.

Like other electric and natural gas utilities and other merchant electric generators, our energy centers, fuel storage facilities, and transmission and distribution facilities may be targets of terrorist activities, including cybersecurity attacks, which could result in disruption of our ability to produce or distribute some portion of our energy products. Any such disruption could result in a significant decrease in revenues or significant additional costs for repair, which could adversely affect on our results of operations, financial position, and liquidity.

Our businesses are dependent on our ability to access

the capital markets successfully. We may not have access to sufficient capital in the amounts and at the times needed.

We use short-term and long-term debt as a significant source of liquidity and funding for capital requirements not satisfied by our operating cash flow, including requirements related to future environmental compliance and capital expenditures required by the IEIMA. As a result of rising costs and increased capital and operations and maintenance expenditures, coupled with regulatory lag, we expect to continue to rely on short-term and long-term debt financing. The inability to raise debt or equity capital on favorable terms, or at all, could negatively affect our ability to maintain and to expand our businesses. After assessing our current operating performance, liquidity, and credit ratings, we believe that Ameren and its rate-regulated businesses will continue to have access to the capital markets. However, events beyond our control, such as a recession or extreme volatility in global debt or equity capital and credit markets, may create uncertainty that could increase our cost of capital or impair or eliminate our ability to access the debt, equity, or credit markets, including our ability to draw on bank credit facilities. Based on projections as of December 31, 2012, of its operating results and cash flows, Genco expects that, by the end of the first quarter of 2013, its interest coverage ratio will be less than the minimum ratio required for the company to borrow additional funds from external, third-party sources. An inability to raise debt could adversely impact Genco's liquidity. Any adverse change in Ameren's or in its subsidiaries' credit ratings may reduce access to capital and trigger additional collateral postings and prepayments. Such changes may also increase the cost of borrowing and fuel, power and natural gas supply, among other things, which could have a material adverse effect on our results of operations, financial position, and liquidity. Certain of the Ameren's subsidiaries rely, in part, on Ameren for access to capital. Circumstances that limit Ameren’s access to capital, including those relating to its other subsidiaries, could impair its ability to provide those Ameren subsidiaries with needed capital. In addition, borrowings directly from Ameren and from the utility and non-state-regulated subsidiary money pools are subject to Ameren’s control and any borrowings are dependent on consideration by Ameren of the facts and circumstances existing at the time of the borrowing request.

Ameren’s holding company structure could limit its ability to pay common stock dividends and to service its debt obligations.

Ameren is a holding company; therefore, its primary assets are the common stock of its subsidiaries. As a result, Ameren’s ability to pay dividends on its common stock depends on the earnings of its subsidiaries and the ability of its subsidiaries to pay dividends or otherwise transfer funds to Ameren. Similarly, Ameren’s ability to service its debt obligations is also dependent upon the earnings of operating subsidiaries and the distribution of those earnings and other payments, including payments of principal and interest under intercompany indebtedness. The payment of dividends to Ameren by its subsidiaries in turn depends on their results of operations and cash flows and other items affecting retained earnings. Ameren’s subsidiaries are

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separate and distinct legal entities and have no obligation, contingent or otherwise, to pay any dividends or make any other distributions (except for payments required pursuant to the terms of intercompany borrowing arrangements and cash payments and receipts under the tax allocation agreement) to Ameren. Certain of the Ameren Companies’ financing agreements and articles of incorporation, in addition to certain statutory and regulatory requirements, may impose restrictions on the ability of such Ameren Companies to transfer funds to Ameren in the form of cash dividends, loans or advances.

Failure to retain and attract key officers and other skilled professional and technical employees could adversely affect on our operations.

Our businesses depend upon our ability to employ and retain key officers and other skilled professional and technical employees. A significant portion of our workforce is nearing retirement, including many employees with specialized skills such as maintaining and servicing our electric and natural gas infrastructure and operating our energy centers.


ITEM 1B.	UNRESOLVED STAFF COMMENTS

None.

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ITEM 2.PROPERTIES

For information on our principal properties, see the energy center table below. See also Liquidity and Capital Resources and Regulatory Matters in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report for a discussion of planned additions, replacements or transfers. See also Note 5 - Long-term Debt and Equity Financings, and Note 15 - Commitments and Contingencies under Part II, Item 8, of this report.

The following table shows what the capability of our energy centers is anticipated to be at the time of our expected 2013 peak summer electrical demand:



Primary Fuel Source	Energy Center	Location	Net Kilowatt Capability^(a)
Ameren Missouri:
Coal	Labadie	Franklin County, Mo.	2,374,000
	Rush Island	Jefferson County, Mo.	1,182,000
	Sioux	St. Charles County, Mo.	972,000
	Meramec	St. Louis County, Mo.	833,000
Total coal			5,361,000
Nuclear	Callaway	Callaway County, Mo.	1,194,000
Hydroelectric	Osage	Lakeside, Mo.	240,000
	Keokuk	Keokuk, Ia.	140,000
Total hydroelectric			380,000
Pumped-storage	Taum Sauk	Reynolds County, Mo.	440,000
Oil (CTs)	Meramec	St. Louis County, Mo.	54,000
	Fairgrounds	Jefferson City, Mo.	54,000
	Mexico	Mexico, Mo.	53,000
	Moberly	Moberly, Mo.	53,000
	Moreau	Jefferson City, Mo.	53,000
	Howard Bend	St. Louis County, Mo.	39,000
Total oil			306,000
Natural gas (CTs)	Audrain^(b)	Audrain County, Mo.	592,000
	Venice^(c)	Venice, Ill.	487,000
	Goose Creek	Piatt County, Ill.	426,000
	Pinckneyville	Pinckneyville, Ill.	312,000
	Raccoon Creek	Clay County, Ill.	296,000
	Kinmundy^(c)	Kinmundy, Ill.	206,000
	Peno Creek^(b)(c)	Bowling Green, Mo.	188,000
	Meramec^(c)	St. Louis County, Mo.	48,000
	Kirksville	Kirksville, Mo.	12,000
Total natural gas			2,567,000
Methane gas (CTs)	Maryland Heights	Maryland Heights, Mo.	8,000
Total Ameren Missouri			10,256,000
Merchant Generation:
Genco:
Coal	Newton	Newton, Ill.	1,215,000
	Joppa (EEI)^(d)	Joppa, Ill.	1,002,000
	Coffeen	Coffeen, Ill.	895,000
Total coal			3,112,000
Natural gas (CTs)	Grand Tower	Grand Tower, Ill.	478,000
	Elgin	Elgin, Ill.	460,000
	Gibson City^(c)	Gibson City, Ill.	228,000
	Joppa 7B	Joppa, Ill.	110,000
	Joppa (EEI)^(d)	Joppa, Ill.	74,000
Total natural gas			1,350,000
Total Genco			4,462,000
AERG:
Coal	E.D. Edwards	Bartonville, Ill.	650,000
	Duck Creek	Canton, Ill.	410,000
Total AERG			1,060,000
Total Merchant Generation			5,522,000
Total Ameren			15,778,000


(a)	Net kilowatt capability is the generating capacity available for dispatch from the energy center into the electric transmission grid.


(b)	There are economic development lease arrangements applicable to these CTs.


(c)	These CTs have the capability to operate on either oil or natural gas (dual fuel).


(d)	Genco owns an 80% interest in EEI. This table reflects the full capability of EEI’s facilities.

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The following table presents electric and natural gas utility-related properties for Ameren Missouri and Ameren Illinois as of December 31, 2012:



	Ameren Missouri		Ameren Illinois
Circuit miles of electric transmission lines^(a)	2,956		4,506
Circuit miles of electric distribution lines	32,967		45,746
Circuit miles of electric distribution lines underground	23	%	15	%
Miles of natural gas transmission and distribution mains	3,282		18,137
Propane-air plants	1		—
Underground gas storage fields	—		12
Billion cubic feet of total working capacity of underground gas storage fields	—		24


(a)	ATXI and EEI own 29 miles and 42 miles of transmission lines, respectively, not reflected in this table.

Our other properties include office buildings, warehouses, garages, and repair shops.

With only a few exceptions, we have fee title to all principal energy centers and other units of property material to the operation of our businesses, and to the real property on which such facilities are located (subject to mortgage liens securing our outstanding first mortgage bonds and to certain permitted liens and judgment liens). The exceptions are as follows:

•

A portion of Ameren Missouri’s Osage energy center reservoir, certain facilities at Ameren Missouri’s Sioux energy center, most of Ameren Missouri’s Peno Creek and Audrain CT energy centers, certain substations, and most transmission and distribution lines and natural gas mains are situated on lands occupied under leases, easements, franchises, licenses, or permits. The United States or the state of Missouri may own or may have paramount rights to certain lands lying in the bed of the Osage River or located between the inner and outer harbor lines of the Mississippi River on which certain of Ameren Missouri’s energy centers and other properties are located.


•	The United States, the state of Illinois, the state of Iowa, or the city of Keokuk, Iowa, may own or may have paramount rights with respect to certain lands lying in the bed of the Mississippi River on which a portion of Ameren Missouri’s Keokuk energy center is located.

Substantially all of the properties and plant of Ameren Missouri and Ameren Illinois are subject to the first liens of the indentures securing their mortgage bonds.

Ameren Missouri has conveyed most of its Peno Creek CT energy center to the city of Bowling Green, Missouri, and leased the energy center back from the city through 2022. Under the terms of this capital lease, Ameren Missouri is responsible for all operation and maintenance for the energy center. Ownership of the energy center will transfer to Ameren Missouri at the expiration of the lease, at which time the property and plant will become subject to the lien of any outstanding Ameren Missouri first mortgage bond indenture.

Ameren Missouri operates a CT energy center located in Audrain County, Missouri. Ameren Missouri has rights and obligations as lessee of the CT energy center under a long-term lease with Audrain County. The lease will expire on December 1, 2023. Under the terms of this capital lease, Ameren Missouri is responsible for all operation and maintenance for the energy center. Ownership of the energy center will transfer to Ameren Missouri at the expiration of the lease, at which time the property and plant will become subject to the lien of any outstanding Ameren Missouri first mortgage bond indenture.


ITEM 3.	LEGAL PROCEEDINGS

We are involved in legal and administrative proceedings before various courts and agencies with respect to matters that arise in the ordinary course of business, some of which involve substantial amounts of money. We believe that the final disposition of these proceedings, except as otherwise disclosed in this report, will not have a material adverse effect on our results of operations, financial position, or liquidity. Risk of loss is mitigated, in some cases, by insurance or contractual or statutory indemnification. We believe that we have established appropriate reserves for potential losses. Material legal and administrative proceedings, which are discussed in Note 2 - Rate and Regulatory Matters and Note 15 - Commitment and Contingencies under Part II, Item 8, of this report and incorporated herein by reference, include the following:


•	appeal of the MoPSC's April 2011 FAC prudence review order and completion of the current FAC prudence review;


•	Ameren Missouri's appeal of the MoPSC's December 2012 electric rate order;


•	Ameren Illinois' appeal of the ICC's 2012 electric distribution rate orders in its initial and update IEIMA filings;


•	natural gas rate proceeding for Ameren Illinois pending before the ICC;


•	FERC litigation to determine wholesale distribution revenues for five of Ameren Illinois' wholesale customers;


•	Entergy's rehearing request of a FERC May 2012 order requiring Entergy to refund to Ameren Missouri additional charges Ameren Missouri paid under an expired power purchase agreement;


•	Ameren Illinois' request for rehearing of a FERC July 2012 order regarding the inclusion of acquisition premiums in Ameren Illinois' transmission rates;


•	ATXI's request for a certificate of public convenience and necessity and project approval from the ICC for the Illinois Rivers project;


•	the EPA's Clean Air Act-related litigation filed against Ameren Missouri, NSR investigations at Genco and AERG, and the Notice of Violation for alleged permitting violations at Genco;


•	remediation matters associated with former MGP and waste disposal sites of the Ameren Companies;


•	litigation associated with the breach of the upper reservoir at Ameren Missouri's Taum Sauk pumped-storage hydroelectric energy center;


•	litigation alleging that the CO₂ emissions from several industrial companies, including Ameren Missouri, Genco,

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and AERG, created atmospheric conditions that intensified Hurricane Katrina;


•	Ameren Illinois' receipt of tax liability notices relating to prior-period electric and natural gas municipal taxes;


•	asbestos-related litigation associated with Ameren, Ameren Missouri, and Ameren Illinois; and


•	Merchant Generation's challenge before the Informal

Conference Board of the Illinois Department of Revenue regarding the State's position that EEI did not qualify for manufacturing tax exemptions for 2010 transactions.


ITEM 4.	MINE SAFETY DISCLOSURES

Not applicable.

EXECUTIVE OFFICERS OF THE REGISTRANTS (ITEM 401(b) OF REGULATION S-K):

The executive officers of the Ameren Companies, including major subsidiaries, are listed below, along with their ages as of December 31, 2012, all positions and offices held with the Ameren Companies as of December 31, 2012 (except as otherwise noted below), tenure as officer, and business background for at least the last five years. Some executive officers hold multiple positions within the Ameren Companies; their titles are given in the description of their business experience.

AMEREN CORPORATION:



Name	Age	Positions and Offices Held
Thomas R. Voss	65	Chairman, President and Chief Executive Officer, and Director
Voss joined Ameren Missouri in 1969. He was elected senior vice president of Ameren Missouri, CIPS, and Ameren Services in 1999, of CILCO in 2003, and of IP in 2004. In 2003, Voss was elected president of Genco; he relinquished his presidency of this company in 2004. In 2006, he was elected executive vice president of Ameren Missouri, CIPS, CILCO and IP. In 2007, Voss was elected chairman, president and chief executive officer of Ameren Missouri, and relinquished his positions at CIPS, CILCO and IP in 2007. In 2009, Voss was elected president and chief executive officer of Ameren; at that time, he relinquished his other positions. In 2010, the Ameren board of directors elected Voss to the additional position of chairman of the board. He has been a member of the Ameren board since 2009.

Martin J. Lyons, Jr.	46	Executive Vice President (Effective January 1, 2013) and Chief Financial Officer
Lyons joined Ameren, Ameren Missouri, CIPS, and Ameren Services in 2001 as controller. He was elected controller of CILCO in 2003. He was also elected vice president of Ameren, Ameren Missouri, CIPS, CILCO, and Ameren Services in 2003 and vice president and controller of IP in 2004. In 2007, his positions at Ameren Missouri were changed to vice president and principal accounting officer. In 2008, Lyons was elected senior vice president and principal accounting officer of the Ameren companies. In 2009, Lyons was also elected chief financial officer of the Ameren companies. Following the Ameren Illinois Merger in 2010, Lyons remained senior vice president, chief financial officer and principal accounting officer of Ameren Illinois. Effective January 1, 2013, Lyons was elected executive vice president and chief financial officer of the Ameren companies, and relinquished his duties as principal accounting officer.

Gregory L. Nelson	55	Senior Vice President, General Counsel and Secretary
Nelson joined Ameren Missouri in 1995 as a manager in the tax department and assumed a similar position with Ameren Services in 1998. Nelson was elected vice president and tax counsel of Ameren Services in 1999 and vice president of Ameren Missouri, CIPS, and CILCO in 2003 and of IP in 2004. In 2010, Nelson was elected vice president, tax and deputy general counsel of Ameren Services. He remained vice president of Ameren Missouri, CIPS, CILCO, and IP. Following the Ameren Illinois Merger in 2010, Nelson remained vice president at Ameren Illinois. In 2011, Nelson was elected to the positions of senior vice president, general counsel and secretary of the Ameren companies.

Bruce A. Steinke	51	Senior Vice President, Finance and Chief Accounting Officer (Effective January 1, 2013)
Steinke joined Ameren Services in 2002 as a manager in the controller's department and head of investor relations. In 2008, he was elected vice president and controller of Ameren, CIPS, CILCO, IP and Ameren Services. In 2009, Steinke relinquished his positions at CIPS, CILCO and IP. Effective January 1, 2013, Steinke was elected senior vice president, finance and chief accounting officer of the Ameren companies.

Jerre E. Birdsong	58	Vice President and Treasurer
Birdsong joined Ameren Missouri in 1977 and was elected treasurer of Ameren Missouri in 1993. He was elected treasurer of Ameren, CIPS and Ameren Services in 1997. In addition to being treasurer, in 2001, Birdsong was elected vice president at Ameren, Ameren Missouri, CIPS, and Ameren Services. Additionally, he was elected vice president and treasurer of CILCO in 2003 and of IP in 2004. Following the Ameren Illinois Merger in 2010, Birdsong, remained vice president and treasurer at Ameren Illinois. Effective February 1, 2013, Birdsong retired from the Ameren companies.

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SUBSIDIARIES:



Name	Age	Positions and Offices Held
Warner L. Baxter	51	Chairman, President and Chief Executive Officer (Ameren Missouri)
Baxter joined Ameren Missouri in 1995 as assistant controller. He was elected senior vice president, finance, of Ameren, Ameren Missouri, CIPS, and Ameren Services in 2001 and of CILCO in 2003. Baxter was elected to the positions of executive vice president and chief financial officer of Ameren, Ameren Missouri, CIPS, CILCO and Ameren Services in 2003 and of IP in 2004. He was elected chairman, president, chief executive officer and chief financial officer of Ameren Services in 2007. In 2009, Baxter was elected chairman, president and chief executive officer of Ameren Missouri; at that time, he relinquished his other positions.

Maureen A. Borkowski	55	Chairman, President and Chief Executive Officer (ATXI)
Borkowski joined Ameren Missouri in 1981. She left the company in 2000 before rejoining Ameren in 2005 as vice president, transmission, of Ameren Services. In 2011, Borkowski was elected chairman, president and chief executive officer of ATXI. In 2011, she was also elected senior vice president, transmission, of Ameren Services.

Daniel F. Cole	59	Chairman, President and Chief Executive Officer (Ameren Services)
Cole joined Ameren Missouri in 1976. He was elected senior vice president of Ameren Missouri and Ameren Services in 1999 and of CIPS in 2001. He was elected senior vice president of CILCO in 2003 and of IP in 2004. In 2009, Cole was elected chairman, president and chief executive officer of Ameren Services and remained senior vice president of Ameren Missouri, CIPS, CILCO and IP. Following the Ameren Illinois Merger in 2010, Cole remained senior vice president at Ameren Illinois.

Adam C. Heflin	48	Senior Vice President and Chief Nuclear Officer (Ameren Missouri)
Heflin joined Ameren Missouri in 2005 as vice president of nuclear operations and was elected senior vice president and chief nuclear officer of Ameren Missouri in 2008.

Richard J. Mark	57	Chairman, President and Chief Executive Officer (Ameren Illinois)
Mark joined Ameren Services in 2002 as vice president of customer service. In 2003, he was elected vice president of governmental policy and consumer affairs at Ameren Services. He was elected senior vice president, customer operations of Ameren Missouri in 2005. In 2007, Mark relinquished his position at Ameren Services. Effective June 13, 2012, Mark relinquished his position at Ameren Missouri and was elected chairman, president and chief executive officer of Ameren Illinois.

Michael L. Moehn	43	Senior Vice President, Customer Operations (Ameren Missouri)
Moehn joined Ameren Services in 2000 as assistant controller. In 2004, Moehn was elected vice president of corporate planning of Ameren Services. In 2008, he was elected senior vice president, corporate planning and business risk management of Ameren Services. Effective January 1, 2012, Moehn relinquished his position at Ameren Services and was elected senior vice president of customer operations of Ameren Illinois. Effective June 13, 2012, Moehn relinquished his position at Ameren Illinois and was elected senior vice president, customer operations of Ameren Missouri.

Charles D. Naslund	60	Executive Vice President (Ameren Services) (Effective March 1, 2013)
Naslund joined Ameren Missouri in 1974. He was elected vice president of power operations at Ameren Missouri in 1999, vice president of Ameren Services in 2000 and vice president of nuclear operations at Ameren Missouri in 2004. He relinquished his position at Ameren Services in 2001. Naslund was elected senior vice president and chief nuclear officer at Ameren Missouri in 2005. In 2008, he was elected chairman, president and chief executive officer of AER. Naslund relinquished his positions at Ameren Missouri in 2008. In 2011, Naslund assumed the position of senior vice president, generation and environmental projects of Ameren Missouri and relinquished his positions of chairman, president and chief executive officer of AER. On January 1, 2013, Naslund relinquished his position at Ameren Missouri and was elected senior vice president of Ameren Services. On March 1, 2013, Naslund was elected executive vice president of Ameren Services.

Steven R. Sullivan	52	Chairman, President and Chief Executive Officer (AER)
After previous service as an Ameren Missouri staff attorney, Sullivan rejoined Ameren, Ameren Missouri, CIPS and Ameren Services in 1998 as vice president and general counsel and later in 1998 was elected secretary. In 2003, Sullivan was elected vice president, general counsel and secretary of CILCO. He was elected senior vice president, general counsel and secretary of Ameren, Ameren Missouri, CIPS, CILCO and Ameren Services in 2003 and of IP in 2004. Following the Ameren Illinois Merger in 2010, Sullivan remained senior vice president, general counsel and secretary at Ameren Illinois. In 2011, Sullivan was elected to the positions of chairman, president and chief executive officer of AER and relinquished his positions of senior vice president, general counsel and secretary of the Ameren companies.

Officers are generally elected or appointed annually by the respective board of directors of each company, following the election of board members at the annual meetings of shareholders. No special arrangement or understanding exists between any of the above-named executive officers and the Ameren Companies nor, to our knowledge, with any other person or persons pursuant to which any executive officer was selected as an officer. There are no family relationships among the officers. All of the above-named executive officers have been employed by an Ameren company for more than five years in executive or management positions.

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PART II


ITEM 5.	MARKET FOR REGISTRANTS' COMMON EQUITY, RELATED STOCKHOLDER MATTERS AND ISSUER PURCHASE OF EQUITY SECURITIES

Ameren’s common stock is listed on the NYSE (ticker symbol: AEE). Ameren common shareholders of record totaled 60,810 on January 31, 2013. The following table presents the price ranges, closing prices, and dividends declared per Ameren common share for each quarter during 2012 and 2011.



	High		Low		Close		Dividends Declared
2012 Quarter Ended:
March 31	$	33.68	$	30.89	$	32.58	$	0.400
June 30	34.04		31.15		33.54		0.400
September 30	35.30		32.27		32.67		0.400
December 31	33.21		28.43		30.72		0.400
2011 Quarter Ended:
March 31	$	29.14	$	26.46	$	28.07	$	0.385
June 30	30.14		27.78		28.84		0.385
September 30	31.44		25.55		29.77		0.385
December 31	34.11		27.98		33.13		0.400

There is no trading market for the common stock of Ameren Missouri and Ameren Illinois. Ameren holds all outstanding common stock of Ameren Missouri and Ameren Illinois.

The following table sets forth the quarterly common stock dividend payments made by Ameren and its subsidiaries during 2012 and 2011:



	2012								2011
(In millions)	Quarter Ended								Quarter Ended
Registrant	December 31		September 30		June 30		March 31		December 31		September 30		June 30		March 31
Ameren Missouri	$	100	$	100	$	100	$	100	$	184	$	84	$	67	$	68
Ameren Illinois	57		57		38		37		89		88		88		62
Ameren	98		97		97		90		96		93		93		93

On February 8, 2013, the board of directors of Ameren declared a quarterly dividend on Ameren’s common stock of 40 cents per share. The common share dividend is payable March 29, 2013, to shareholders of record on March 13, 2013.

For a discussion of restrictions on the Ameren Companies’ payment of dividends, see Liquidity and Capital Resources in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, of this report.

Purchases of Equity Securities

The following table presents Ameren Corporation’s purchases of equity securities reportable under Item 703 of Regulation S-K:



Period	(a) Total Number of Shares (or Units) Purchased^(a)	(b) Average Price Paid per Share (or Unit)		(c) Total Number of Shares (or Units) Purchased As Part of Publicly Announced Plans or Programs	(d) Maximum Number (or Approximate Dollar Value) of Shares (or Units) That May Yet Be Purchased Under the Plans or Programs
October 1 – October 31, 2012	—	$	—	—	—
November 1 – November 30, 2012	300	29.32		—	—
December 1 – December 31, 2012	3,213	29.52		—	—
Total	3,513	$	29.50	—	—


(a)	Comprised of shares of Ameren common stock purchased in open-market transactions pursuant to Ameren’s 2006 Omnibus Incentive Compensation Plan in satisfaction of Ameren’s obligation to distribute shares of common stock for vested performance units. Ameren does not have any publicly announced equity securities repurchase plans or programs.

Ameren Missouri and Ameren Illinois did not purchase equity securities reportable under Item 703 of Regulation S-K during the period from October 1, 2012 to December 31, 2012.

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Performance Graph

The following graph shows Ameren’s cumulative total shareholder return during the five years ended December 31, 2012. The graph also shows the cumulative total returns of the S&P 500 Index and the Edison Electric Institute Index (EEI Index), which comprises most investor-owned electric utilities in the United States. The comparison assumes that $100 was invested on December 31, 2007, in Ameren common stock and in each of the indices shown, and it assumes that all of the dividends were reinvested.



December 31,	2007		2008		2009		2010		2011		2012
Ameren	$	100.00	$	65.41	$	58.40	$	62.41	$	77.23	$	75.28
S&P 500 Index	100.00		63.00		79.67		91.67		93.60		108.58
EEI Index	100.00		74.10		82.04		87.81		105.36		107.57

Ameren management cautions that the stock price performance shown in the graph above should not be considered indicative of potential future stock price performance.

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ITEM 6.	SELECTED FINANCIAL DATA



For the years ended December 31, (In millions, except per share amounts)	2012			2011		2010		2009		2008
Ameren^(a):
Operating revenues	$	6,828		$	7,531	$	7,638	$	7,135	$	7,869
Operating income (loss)^(b)	(1,240		)	1,241		916		1,416		1,362
Net income (loss) attributable to Ameren Corporation	(974		)	519		139		612		605
Common stock dividends	382			375		368		338		534
Earnings (loss) per share - basic and diluted	(4.01		)	2.15		0.58		2.78		2.88
Common stock dividends per share	1.60			1.555		1.54		1.54		2.54
As of December 31:
Total assets	$	21,835		$	23,645	$	23,511	$	23,702	$	22,671
Long-term debt, excluding current maturities	6,626			6,677		6,853		7,111		6,554
Total Ameren Corporation stockholders’ equity	6,616			7,919		7,730		7,856		6,963
Ameren Missouri:
Operating revenues	$	3,272		$	3,383	$	3,197	$	2,874	$	2,960
Operating income^(c)	845			609		711		566		514
Net income available to common stockholder	416			287		364		259		245
Dividends to parent	400			403		235		175		264
As of December 31:
Total assets	$	13,043		$	12,757	$	12,504	$	12,219	$	11,529
Long-term debt, excluding current maturities	3,801			3,772		3,949		4,018		3,673
Total stockholders’ equity	4,054			4,037		4,153		4,057		3,562
Ameren Illinois:
Operating revenues	$	2,525		$	2,787	$	3,014	$	2,984	$	3,508
Operating income	377			458		498		363		191
Income from continuing operations	144			196		212		133		41
Net income available to common stockholder	141			193		248		241		87
Dividends to parent	189			327		133		98		60
As of December 31:
Total assets^(d)	$	7,282		$	7,213	$	7,406	$	8,298	$	8,023
Long-term debt, excluding current maturities	1,577			1,657		1,657		1,847		1,850
Total stockholders’ equity	2,401			2,452		2,576		3,072		2,655


(a)	Includes amounts for Ameren registrant and nonregistrant subsidiaries and intercompany eliminations.


(b)	Includes “Impairment and other charges” of $2,578 million, $125 million and $589 million recorded at Ameren during the years ended December 31, 2012, 2011, and 2010, respectively.


(c)	Includes “Loss from regulatory disallowance” of $89 million recorded during the year ended December 31, 2011.


(d)	Includes total assets from discontinued operations of $1,117 million and $1,081 million at December 31, 2009 and 2008, respectively.

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ITEM 7.	MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

OVERVIEW

Ameren Executive Summary

Operations

In December 2012, Ameren determined that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously estimated useful lives of that business segment's long-lived assets. This determination resulted from Ameren's analysis of the current and projected future financial condition of its Merchant Generation business, including the need to fund Genco debt maturities beginning in 2018, and its conclusion that this business was no longer a core component of its future business strategy. The volatility of earnings and cash flows of the Merchant Generation business, as well as the high degree of uncertainty regarding future returns on incremental capital invested in this business, are not in alignment with Ameren's current strategy. Ameren's decision to exit the business follows a trend of decreasing earnings and cash flows from the Merchant Generation business since 2008. Ameren's date and method of exit from the Merchant Generation business is currently uncertain with a sale or restructuring possible. Senior management and Ameren's board of directors are focused on maximizing the overall benefit to Ameren consistent with its legal obligations.

While working to exit the Merchant Generation business, Ameren remains focused on its rate-regulated utilities, including growing investments in jurisdictions with constructive regulatory frameworks. Ameren continues to seek modern, constructive regulatory frameworks, which provide timely cash flows and a reasonable opportunity to earn fair returns on investments that are in the best long-term interest of Ameren's customers. These frameworks support Ameren's rate-regulated businesses' ability to obtain cash on a timelier basis, to reinvest in energy infrastructure and also attract capital on terms that facilitate timely investments to modernize their aging infrastructure.

In December 2012, the MoPSC issued an order approving an increase for Ameren Missouri in annual revenues for electric service of $260 million. These new rates became effective on January 2, 2013. The MoPSC's December 2012 electric rate order improved Ameren Missouri's regulatory framework for energy efficiency programs as well as authorized the implementation of a new storm restoration cost tracking mechanism.

In 2012, Ameren Illinois elected to participate in the IEIMA's performance-based formula ratemaking framework. The IEIMA was designed to promote investment in electric grid modernization and create jobs through the establishment of formula ratemaking for electric delivery service. Ameren Illinois believes the ICC has incorrectly implemented the IEIMA in both of its 2012 electric delivery service rate orders. As a result, Ameren Illinois has appealed both 2012 electric delivery service rate orders to the Appellate Court of the Fourth District of Illinois and is also seeking a legislative solution to address the ICC's

implementation of the IEIMA. Additionally, in January 2013, Ameren Illinois filed a request with the ICC to increase its annual revenues for natural gas delivery service by $50 million. This request was based on a 2014 future test year.

Ameren continues to proceed with its plans to increase its investment in FERC-regulated electric transmission. In 2013, for both Ameren Illinois and ATXI, transmission rates will be updated annually based on a forward-looking calculation with a revenue requirement reconciliation. Ameren expects to invest a total of approximately $2.2 billion in FERC-regulated transmission projects over the next five years. The Ameren Illinois portion of that total, approximately $1 billion, is for projects focused on local load growth and reliability needs. ATXI, through its construction of three MISO-approved regional multi-value electric transmission projects, expects to invest approximately $1.2 billion over the next five years. In November 2012, ATXI filed a request with the ICC for a certificate of public convenience and necessity for the Illinois Rivers project. Once ATXI receives the certificate of public convenience and necessity, it can begin to acquire right of way for the Illinois Rivers project. A full range of construction activities for the Illinois Rivers project is expected to begin in 2014.

Earnings

Ameren reported a net loss of $974 million, or $4.01 per share, for 2012 compared with net income of $519 million, or $2.15 per share, in 2011. The main factor contributing to the net loss in 2012, compared with net income in 2011, was the 2012 impairments of Merchant Generation's long-lived assets resulting from Ameren's determination in December 2012 that it intends to, and it is probable that it will, exit its Merchant Generation business before the end of the previously useful lives of that business segment's long-lived assets, coupled with the sharp decline in the market price for power in the first quarter of 2012. The decline in Merchant Generation earnings also reflected lower power prices and higher fuel costs. Ameren's earnings also decreased in 2012, compared with 2011, because of a decline in Ameren Illinois' earnings primarily due to the impacts of implementing the IEIMA's formula ratemaking in 2012, including a lower allowed return on equity and required nonrecoverable contributions, as well as lower natural gas sales volumes as a result of warmer 2012 winter temperatures. Summer weather was much warmer than normal in 2012, but similar to 2011. The earnings declines in the Merchant Generation and Ameren Illinois segments were partially offset by increased Ameren Missouri earnings due primarily to the full year effect of the 2011 electric rate increase as well as lower operations and maintenance expense reflecting the absence of a refueling outage at the Callaway energy center in 2012, decreased labor costs primarily due to staff reductions resulting from the 2011 voluntary separation plan, and reduced major storm-related costs. Ameren Missouri's 2012 earnings, compared to 2011 earnings, also benefited from a favorable 2012 FERC order related to a disputed power purchase agreement that expired in 2009 and the absence of a 2011 charge to earnings related to the FAC. These positive Ameren Missouri factors were partially offset by higher

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depreciation expense and lower electric sales volumes due to warmer 2012 winter temperatures.

Liquidity

Cash flows from operations of $1.7 billion were used to pay dividends to common stockholders of $382 million and to fund capital expenditures of $1.2 billion. At December 31, 2012, Ameren, on a consolidated basis, had available liquidity, in the form of cash on hand and amounts available under existing credit agreements, of approximately $2.3 billion, which was a $100 million increase from the amount of available liquidity at December 31, 2011.

Capital Spending

From 2013 through 2017, Ameren's cumulative capital spending is projected to range between $7.4 billion and $9.5 billion. Much of this spending is at Ameren's rate-regulated utilities, including a total of approximately $1.2 billion at ATXI to invest in its electric transmission assets as discussed above. The Merchant Generation segment's capital spending is expected to be up to $385 million from 2013 through 2017, assuming Ameren continues to own the Merchant Generation energy centers for the entire period.

General

Ameren, headquartered in St. Louis, Missouri, is a public utility holding company under PUHCA 2005, administered by FERC. Ameren’s primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. These subsidiaries operate, as the case may be, rate-regulated electric generation, transmission, and distribution businesses, rate-regulated natural gas transmission and distribution businesses, and merchant electric generation businesses. Dividends on Ameren’s common stock and the payment of other expenses by Ameren depend on distributions made to it by its subsidiaries. Ameren’s principal subsidiaries are listed below. See Note 1 - Summary of Significant Accounting Policies under Part II, Item 8, of this report for a detailed description of our principal subsidiaries.


•	Ameren Missouri operates a rate-regulated electric generation, transmission, and distribution business, and a rate-regulated natural gas transmission and distribution business in Missouri.


•	Ameren Illinois operates a rate-regulated electric and natural gas transmission and distribution business in Illinois.


•	AER consists of non-rate-regulated operations, including Genco, AERG, Marketing Company, and through Genco, an 80% ownership interest in EEI, which Ameren consolidates for financial reporting purposes.

financial condition of its Merchant Generation business segment, including the need to fund Genco debt maturities beginning in 2018, and its conclusion that this business segment is no longer a core component of its future business strategy. In consideration of this determination, Ameren has begun planning to reduce, and ultimately eliminate, the Merchant Generation business segment’s, including Genco's, reliance on Ameren’s financial support and shared services support. Furthermore, Ameren recorded a noncash long-lived asset impairment charge to reduce the carrying values of the Merchant Generation energy centers, except for the Joppa coal-fired energy center, to their estimated fair values. See Note 17 - Impairment and Other Charges under Part II, Item 8, for additional information. Ameren's date and method of exit from the Merchant Generation business is currently uncertain. Exit strategies may include the sale of all or parts of the Merchant Generation business and the restructuring of all or a portion of Ameren's equity position in Genco. Ameren's Merchant Generation long-lived assets have not been classified as held-for-sale under authoritative accounting guidance as all criteria to qualify for that presentation were not met as of December 31, 2012. Specifically, Ameren did not consider it probable that a disposition would occur within one year.

On October 1, 2010, Ameren, CIPS, CILCO, IP, AERG and AER completed a two-step corporate internal reorganization. The first step of the reorganization was the Ameren Illinois Merger. The second step of the reorganization involved the distribution of AERG stock from Ameren Illinois to Ameren and the subsequent contribution by Ameren of the AERG stock to AER. Ameren Illinois segregated AERG’s operating results and cash flows and presented them separately as discontinued operations in its consolidated statement of income and consolidated statement of cash flows, respectively, for all periods presented prior to October 1, 2010, in this report. See Note 16 - 2010 Corporate Reorganization under Part II, Item 8, for additional information.

The financial statements of Ameren and Ameren Illinois are prepared on a consolidated basis and therefore include the accounts of their respective majority-owned subsidiaries. Ameren Illinois' financial statements are consolidated because Ameren Illinois included AERG in its statements of income and cash flows during 2010. Ameren Missouri has no subsidiaries, and therefore its financial statements are not prepared on a consolidated basis. All significant intercompany transactions have been eliminated. All tabular dollar amounts are in millions, unless otherwise indicated.

In addition to presenting results of operations and earnings amounts in total, we present certain information in cents per share. These amounts reflect factors that directly affect Ameren’s earnings. We believe that this per share information helps readers to understand the impact of these factors on Ameren’s earnings per share. All references in this report to earnings per share are based on average diluted common shares outstanding.

RESULTS OF OPERATIONS

Our results of operations and financial position are affected

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by many factors. Weather, economic conditions, and the actions of key customers or competitors can significantly affect the demand for our services. Our results are also affected by seasonal fluctuations: winter heating and summer cooling demands. The vast majority of Ameren’s revenues are subject to state or federal regulation. This regulation has a material impact on the prices we charge for our services. Merchant Generation sales are also subject to market conditions for power. We principally use coal, nuclear fuel, natural gas, methane gas, and oil for fuel in our operations. The prices for these commodities can fluctuate significantly because of the global economic and political environment, weather, supply and demand, and many other factors. We have natural gas cost recovery mechanisms for our Illinois and Missouri natural gas delivery service businesses, a purchased power cost recovery mechanism for our Illinois electric delivery service business, and a FAC for our Missouri electric utility business. Ameren Illinois' electric delivery service utility business, pursuant to the IEIMA, conducts an annual reconciliation of the revenue requirement necessary to reflect the actual costs incurred in a given year with the revenue requirement that was in effect for that year, with recoveries from or refunds to customers in a subsequent year. Included in Ameren Illinois' revenue requirement reconciliation is a formula for the return on equity, which is equal to the average of the monthly yields of 30-year United States treasury bonds plus 590 basis points for 2012 and 580 basis points thereafter. Therefore, Ameren Illinois' annual return on equity will be directly correlated to yields on United States treasury bonds. Fluctuations in interest rates and conditions in the capital and credit markets also affect our cost of borrowing and our pension and postretirement benefits costs. We employ various risk management strategies to reduce our exposure to commodity risk and other risks inherent in our business. The reliability of our energy centers and transmission and distribution systems and the level of purchased power costs, operations and maintenance costs, and capital investment are key factors that we seek to control to optimize our results of operations, financial position, and liquidity.

Earnings Summary

Net loss attributable to Ameren Corporation was $974 million, or $4.01 per share, for 2012. Net income attributable to Ameren Corporation was $519 million, or $2.15 per share, for 2011, and $139 million, or $0.58 per share, for 2010.

2012 versus 2011

The net loss attributable to Ameren Corporation in 2012 was primarily caused by a net loss in the Merchant Generation segment of $1.516 billion in 2012. The Merchant Generation segment reported net income of $45 million in 2011. Net income attributable to Ameren Corporation in 2012 decreased in the Ameren Illinois Segment by $52 million from 2011 and increased in the Ameren Missouri segment by $129 million from 2011.

Compared with 2011 earnings per share, 2012 earnings were unfavorably affected by:


•	the 2012 impairments of Merchant Generation's long-lived assets resulting from Ameren's determination in December

2012 that it intends to, and it is probable that it will, exit its Merchant Generation segment before the end of the previously estimated useful lives of that business segment's long-lived assets, coupled with the sharp decline in the market price of power in the first quarter of 2012 ($6.42 per share);


•	lower electric margins in the Merchant Generation segment, largely due to reduced generation volumes caused by lower market prices for power as well as higher fuel and related transportation costs (34 cents per share);


•	a reduction in Ameren Illinois' electric earnings primarily caused by a lower allowed return on equity under electric delivery service formula ratemaking and required donations pursuant to the IEIMA (17 cents per share);


•	reduced electric and natural gas demand as a result of warmer 2012 winter temperatures (estimated at 7 cents per share); and


•	reduced rate-regulated retail sales volumes, excluding the effects of abnormal weather, as sales volumes declined due to continued economic pressure, energy efficiency measures, and customer conservation efforts, among other items (2 cents per share).

Compared with 2011 earnings per share, 2012 earnings were favorably affected by:


•	the absence in 2012 of charges recorded in 2011 at Ameren Missouri for the MoPSC's July 2011 disallowance of costs of enhancements relating to the rebuilding of Ameren Missouri's Taum Sauk energy center in excess of amounts recovered from property insurance and at Merchant Generation for the closure of the Meredosia and Hutsonville energy centers (32 cents per share);

•

higher utility rates at Ameren Missouri and Ameren Illinois. Ameren Missouri's electric rates increased pursuant to an order issued by the MoPSC, which became effective in July 2011. The favorable impact of the Ameren Missouri rate increase on earnings was reduced by the increased regulatory asset amortization directed by the rate order. Ameren Illinois' natural gas rates increased pursuant to an order issued by the ICC, which became effective in mid-January 2012 (22 cents per share);


•	the absence in 2012 of a Callaway energy center refueling and maintenance outage (11 cents per share);


•	reduction in operations and maintenance expenses at both Ameren Missouri and Merchant Generation energy centers due to fewer outages and a reduction in employees (10 cents per share);


•	the impact of fewer major storms on operations and maintenance expenses (9 cents per share);


•	a reduction in Ameren Missouri's purchased power expense and an increase in interest income, each as a result of a FERC-ordered refund received in 2012 from Entergy for a power purchase agreement that expired in 2009 (7 cents per share);


•	the absence in 2012 of a 2011 charge associated with voluntary separation offers to eligible Ameren Missouri and Ameren Services employees (7 cents per share);


•	the absence in 2012 of a reduction in Ameren Missouri's

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revenues as a result of the MoPSC's April 2011 FAC prudence review order covering the period from March 1, 2009, to September 30, 2009, which resulted in Ameren Missouri recording an obligation to refund to its electric customers the earnings associated with certain previously recognized sales (5 cents per share); and

•

a decrease in Merchant Generation depreciation and amortization expense due to the asset impairments recorded in 2012, a change in 2011 in the estimates relating to asset retirement obligations, and the closure of the Meredosia and Hutsonville energy centers at the end of 2011, which was partially offset by an increase in Ameren Missouri depreciation and amortization expense caused primarily by the installation of scrubbers at the Sioux energy center (4 cents per share).

The cents per share information presented above is based on average shares outstanding in 2011.

2011 versus 2010

Net income attributable to Ameren Corporation increased $380 million, and earnings per share increased $1.57 in 2011 compared with 2010. The Merchant Generation segment reported net income attributable to Ameren Corporation of $45 million in 2011, compared with a $409 million net loss in 2010. Net income attributable to Ameren Corporation decreased in the Ameren Missouri segment and Ameren Illinois Segment by $77 million and $15 million, respectively, in 2011 compared with 2010.

Compared with 2010 earnings per share, 2011 earnings were favorably affected by:


•	reduced impairment and other charges in the Merchant Generation segment, offset in part by a charge to earnings related to the MoPSC’s July 2011 disallowance of costs of enhancements relating to the rebuilding of the Taum Sauk energy center in excess of amounts recovered from property insurance ($1.87 per share);

•

higher Ameren Missouri electric rates pursuant to orders issued by the MoPSC, which became effective in June 2010 and in July 2011, as well as higher Ameren Missouri natural gas rates pursuant to a MoPSC order, which became effective in late February 2011. The impact of the Ameren Missouri electric rate increases on earnings was reduced by the adoption of life span depreciation methodology, recognition in 2010 of regulatory assets for previously expensed costs in the prior-year period, and increased regulatory asset amortization as directed by the rate orders (17 cents per share). These amounts exclude the unfavorable impact of the charge to earnings related to the MoPSC’s disallowance of Taum Sauk rebuilding costs discussed above;


•	lower interest expense, primarily due to the maturity and repayment of $200 million of Merchant Generation’s senior secured notes in November 2010, the redemption of $66 million of Ameren Missouri’s subordinated deferrable interest debentures in September 2010, Ameren Illinois’ redemptions of $150 million of senior secured notes and $40 million of

first mortgage bonds in June 2011 and September 2010, respectively, and a reduction in borrowings under credit facility agreements (12 cents per share);


•	higher Ameren Illinois electric rates pursuant to orders issued by the ICC in 2010 (6 cents per share);


•	the absence in 2011 of a charge for the impact on deferred taxes from changes in federal health care laws (6 cents per share);


•	the absence in 2011 of charges recorded in 2010 for cancelled or unrecoverable projects at Ameren Missouri (6 cents per share);


•	a reduction in operations and maintenance expense related to plant maintenance, primarily at Ameren Missouri, as fewer costs were incurred for major outages at coal-fired energy centers because the scope of the outages in 2011 was not as extensive as the scope of the outages conducted in 2010 (5 cents per share); and


•	reduction in expense as a result of disciplined cost management efforts to align spending with regulatory outcomes and economic conditions.

Compared with 2010 earnings per share, 2011 earnings were unfavorably affected by:


•	lower electric margins in the Merchant Generation segment, largely due to lower realized revenue per megawatthour sold and higher fuel and related transportation costs (21 cents per share). This amount excludes the unfavorable impacts of net unrealized MTM activity discussed below;


•	reduced rate-regulated retail sales volumes, excluding the effects of abnormal weather, as sales volumes declined due to continued economic pressure, energy efficiency measures, and customer conservation efforts as well as lower wholesale sales at Ameren Missouri due to a reduction in customers and the expiration of favorably priced contracts, among other items (15 cents per share);


•	unrealized net losses on MTM activity primarily related to nonqualifying power hedges and fuel-related contracts as well as unfavorable changes in the market value of investments used to support Ameren’s deferred compensation plans (10 cents per share);


•	the impact of weather conditions on electric and natural gas demand (estimated at 10 cents per share);


•	increased operations and maintenance expenses as a result of major storms in 2011 (9 cents per share);


•	a reduction in allowance for equity funds used during construction reflecting the 2010 completion of two scrubbers at Ameren Missouri’s Sioux energy center (8 cents per share);


•	increased operations and maintenance expenses associated with voluntary separation offers to eligible Ameren Missouri and Ameren Services employees during 2011 (7 cents per share);


•	a reduction in revenues resulting from the MoPSC’s April 2011 order with respect to its FAC review for the period from March 1, 2009, to September 30, 2009, as discussed above. See Note 2 - Rate and Regulatory Matters under Part II, Item 8, of this report for additional information (5 cents per share); and

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•	an increase in depreciation and amortization expense caused primarily by the installation of scrubbers at Ameren Missouri’s Sioux energy center as well as other capital additions (4 cents per share).

The cents per share information presented above is based on average shares outstanding in 2010.

For additional details regarding the Ameren Companies’ results of operations, including explanations of Margins, Other Operations and Maintenance Expenses, Impairment and Other Charges, Depreciation and Amortization, Taxes Other Than Income Taxes, Other Income and Expenses, Interest Charges, and Income Taxes, see the major headings below.

Below is a table of income statement components by segment for the years ended December 31, 2012, 2011, and 2010:



2012	Ameren Missouri			Ameren Illinois Segment			Merchant Generation			Other / Intersegment Eliminations			Total
Electric margins	$	2,340		$	1,034		$	518		$	(11	)	$	3,881
Natural gas margins	75			378			—			(1		)	452
Other revenues	1			—			—			(1		)	—
Other operations and maintenance	(827		)	(684		)	(259		)	18			(1,752		)
Impairment and other charges	—			—			(2,578		)	—			(2,578		)
Depreciation and amortization	(440		)	(221		)	(102		)	(12		)	(775		)
Taxes other than income taxes	(304		)	(130		)	(25		)	(9		)	(468		)
Other income and (expenses)	49			(10		)	(1		)	(4		)	34
Interest charges	(223		)	(129		)	(95		)	(1		)	(448		)
Income (taxes) benefit	(252		)	(94		)	1,019			7			680
Net income (loss)	419			144			(1,523		)	(14		)	(974		)
Noncontrolling interest and preferred dividends	(3		)	(3		)	7			(1		)	—
Net income (loss) attributable to Ameren Corporation	$	416		$	141		$	(1,516	)	$	(15	)	$	(974	)
2011
Electric margins	$	2,252		$	1,087		$	668		$	(10	)	$	3,997
Natural gas margins	79			354			—			(2		)	431
Other revenues	5			1			3			(9		)	—
Other operations and maintenance	(934		)	(640		)	(285		)	39			(1,820		)
Impairment and other charges	(89		)	—			(37		)	1			(125		)
Depreciation and amortization	(408		)	(215		)	(143		)	(19		)	(785		)
Taxes other than income taxes	(296		)	(129		)	(24		)	(8		)	(457		)
Other income and (expenses)	51			1			1			(7		)	46
Interest charges	(209		)	(136		)	(105		)	(1		)	(451		)
Income (taxes) benefit	(161		)	(127		)	(32		)	10			(310		)
Net income (loss)	290			196			46			(6		)	526
Noncontrolling interest and preferred dividends	(3		)	(3		)	(1		)	—			(7		)
Net income (loss) attributable to Ameren Corporation	$	287		$	193		$	45		$	(6	)	$	519
2010
Electric margins	$	2,233		$	1,096		$	780		$	(17	)	$	4,092
Natural gas margins	75			375			—			(2		)	448
Other revenues	1			—			—			(1		)	—
Other operations and maintenance	(931		)	(635		)	(287		)	32			(1,821		)
Impairment and other charges	—			—			(589		)	—			(589		)
Depreciation and amortization	(382		)	(210		)	(146		)	(27		)	(765		)
Taxes other than income taxes	(285		)	(128		)	(26		)	(10		)	(449		)
Other income and (expenses)	70			(6		)	1			(8		)	57
Interest charges	(213		)	(143		)	(133		)	(8		)	(497		)
Income (taxes) benefit	(199		)	(137		)	(6		)	17			(325		)
Net income (loss)	369			212			(406		)	(24		)	151
Noncontrolling interest and preferred dividends	(5		)	(4		)	(3		)	—			(12		)
Net income (loss) attributable to Ameren Corporation	$	364		$	208		$	(409	)	$	(24	)	$	139

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Margins

The following table presents the favorable (unfavorable) variations by segment for electric and natural gas margins from the previous year. Electric margins are defined as electric revenues less fuel and purchased power costs. Natural gas margins are defined as gas revenues less gas purchased for resale. The table covers the years ended December 31, 2012, 2011, and 2010. We consider electric and natural gas margins useful measures to analyze the change in profitability of our electric and natural gas operations between periods. We have included the analysis below as a complement to the financial information we provide in accordance with GAAP. However, these margins may not be a presentation defined under GAAP, and may not be comparable to other companies’ presentations or more useful than the GAAP information we provide elsewhere in this report.



2012 versus 2011	Ameren Missouri			Ameren Illinois Segment			Merchant Generation		Other^(a)		Ameren
Electric revenue change:
Effect of weather (estimate)^(b)	$	(19	)	$	(1	)	$	—	$	—	$	(20	)
Regulated rates:

Ameren Illinois Co 10-K