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REGULATORY MATTERS - APC Rate RSE (Details) - Alabama Power - USD ($) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2025 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2024 | Oct. 03, 2023 | Feb. 28, 2022
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Rate adjustment period |  | 2 years |  |  |  |  |
Maximum percentage of rate RSE |  | 4.00% |  |  |  |  |
Maximum annual percentage of ratio rate |  | 5.00% |  |  |  |  |
Adjusting point of weighted cost of equity |  | 5.98% |  |  |  |  |
Percent of basis points |  | 0.07% |  |  |  |  |
Authorized ROE |  | 52.30% | 52.20% |  |  |  |
Customer refundable fees, refund payments, tranche one, percentage |  | 25.00% |  |  |  |  |
Customer refundable fees, refund payments, tranche two, percentage |  | 40.00% |  |  |  |  |
Customer refundable fees, refund payments, tranche two, percentage |  | 75.00% |  |  |  |  |
Customer refundable fees, refund payments, tranche one, review year with rate RSE upward adjustment, percentage |  | 50.00% |  |  |  |  |
Contract with customer, liability, bill credits |  |  |  |  |  |  | $ 55
Rate RSE refund liability |  | $ 15 | $ 62 | $ 181 |  |  |
Rate RSE refund liability, portion attributable to reduce under recovered balance |  |  |  |  |  |  | $ 126
Customer refund |  | 304 |  |  |  |  |
Deferred income taxes |  | $ 81 |  |  |  | $ 24 |
Minimum |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Public utilities, actual weighted common equity return, threshold, percentage |  | 6.15% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche one |  | 6.15% | 6.15% | 6.15% |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche two |  | 6.65% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche three |  | 7.15% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold, review year with rate RSE upward adjustment, percentage |  | 6.15% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage, tranche one |  | 6.15% |  |  |  |  |
Maximum |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Public utilities, actual weighted common equity return, threshold, percentage |  | 7.65% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche one |  | 6.65% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche two |  | 7.15% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, percentage, tranche three |  | 7.65% |  |  |  |  |
Customer refundable fees, refund payments, percentage |  | 7.65% |  |  |  |  |
Public utilities, actual weighted common equity return, threshold for customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage, tranche one |  | 6.90% |  |  |  |  |
Customer refundable fees, refund payments, review year with rate RSE upward adjustment, percentage |  | 6.90% |  |  |  |  |
Scenario, Forecast |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Authorized ROE | 55.00% |  |  |  |  |  |
Deferred income taxes | $ 14 |  |  |  | $ 67 |  |

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