REGULATORY MATTERS (Regulatory Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Regulatory Liabilities [Line Items]
Regulatory Liabilities, Remaining Recovery Period (years)	1 year
Total Regulatory Liabilities	$ 563,000	$ 506,000
Less Current Portion	143,851	142,844
Total Noncurrent Regulatory Liabilities	419,132	362,859
Income Taxes Recoverable through Future Rates
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	199,000	209,000
Renewable Energy Standard
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	102,000	88,000
Deferred Investment Tax Credits
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	94,000	4,000
Net Cost of Removal
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	75,000	110,000
Pension and Other Postretirement Benefits (Note 9)
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 32,000	19,000
Over-Recovered Fuel and Purchased Energy Costs
Regulatory Liabilities [Line Items]
Regulatory Liabilities, Remaining Recovery Period (years)	1 year
Total Regulatory Liabilities	$ 32,000	49,000
Derivatives (Note 12)
Regulatory Liabilities [Line Items]
Regulatory Liabilities, Remaining Recovery Period (years)	4 years
Total Regulatory Liabilities	$ 20,000	22,000
Demand Side Management
Regulatory Liabilities [Line Items]
Regulatory Liabilities, Remaining Recovery Period (years)	1 year
Total Regulatory Liabilities	$ 9,000	$ 5,000

TUCSON ELECTRIC POWER CO 10-K