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v3.25.3

Acquisitions and Dispositions - Narrative (Details) $ in Millions | Jul. 30, 2025 USD ($) | Jun. 06, 2025 USD ($) | Sep. 30, 2025 USD ($) MW | Jun. 19, 2025
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MISSISSIPPI POWER CO | Plant Daniel Units 1 and 2 |  |  |  |
Business Combination [Line Items] |  |  |  |
Proportionate ownership share |  |  |  | 50.00%
Proceeds from acquisition | $ | $ 36 |  |  |
ALABAMA POWER CO | Tenaska Alabama Partners, L.P. |  |  |  |
Business Combination [Line Items] |  |  |  |
Purchase price | $ |  | $ 635 |  |
Assets recorded in PPE | $ |  | $ 622 |  |
Approximate nameplate capacity | MW |  |  | 855 |
Millers Branch Solar Development Phase 1 | SOUTHERN POWER CO |  |  |  |
Business Combination [Line Items] |  |  |  |
Approximate nameplate capacity | MW |  |  | 200 |
Millers Branch Solar Development Phase 2 | SOUTHERN POWER CO |  |  |  |
Business Combination [Line Items] |  |  |  |
Approximate nameplate capacity | MW |  |  | 180 |
Millers Branch Solar Development Phase 3 | SOUTHERN POWER CO |  |  |  |
Business Combination [Line Items] |  |  |  |
Approximate nameplate capacity | MW |  |  | 132 |
Millers Branch Solar Development | SOUTHERN POWER CO |  |  |  |
Business Combination [Line Items] |  |  |  |
Approximate nameplate capacity | MW |  |  | 512 |
Construction work in progress | $ |  |  | $ 661 |
Wind Facilities | SOUTHERN POWER CO |  |  |  |
Business Combination [Line Items] |  |  |  |
Construction work in progress | $ |  |  | $ 165 |

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