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REGULATORY MATTERS - APC Certificate of Convenience and Necessity and RGC (Details) $ in Millions | 12 Months Ended |  |  |  |  |
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Dec. 31, 2020 MW | Dec. 31, 2023 USD ($) | Jun. 14, 2023 MW | Jun. 13, 2023 MW | Apr. 04, 2023 claim MW | Dec. 31, 2022 USD ($)
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Plant in service, net of depreciation | $ |  | $ 90,703 |  |  |  | $ 82,232
Approved solar PPAs | claim |  |  |  |  | 2 |
Alabama Power |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Plant in service, net of depreciation | $ |  | $ 24,298 |  |  |  | $ 23,002
Renewable generation certificate, authorized generating capacity (in MWs) |  |  |  |  | 500 |
Additional generating capacity (in MWs) |  |  |  |  | 160 |
Renewable generation certificate, generating capacity (in MWs) |  |  |  |  | 490 |
Additional renewable capacity (in MWs) |  |  | 2,400 |  |  |
Size of allowable projects (in MWs) |  |  | 200 | 80 |  |
Approval limit (in MWs) |  |  | 400 | 160 |  |
Plant Barry Unit 8 | Alabama Power |  |  |  |  |  |
Schedule of Regulatory Assets and Liabilities [Line Items] |  |  |  |  |  |
Approximate nameplate capacity (in MWs) | 720 |  |  |  |  |

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- Details
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