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Jointly-Owned Electric Utility Plant | 12 Months Ended
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Dec. 31, 2023
Jointly-Owned Electric Utility Plant | JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0% |  | $632 |  | $264 |  | $7
George Neal Unit 4 | 25.7% |  | 196 |  | 107 |  | 6
George Neal Unit 3 | 28.0% |  | 181 |  | 85 |  | 8
Louisa Unit 1 | 4.0% |  | 44 |  | 22 |  | —
|  |  | 1,053 |  | 478 |  | 21
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 53.5% |  | 818 |  | 361 |  | 6
West Riverside Energy Center and Solar Facility (a) | 73.8% |  | 581 |  | 60 |  | 6
Forward Wind Energy Center | 42.6% |  | 118 |  | 53 |  | —
|  |  | 1,517 |  | 474 |  | 12
Alliant Energy |  |  | $2,570 |  | $952 |  | $33
(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.
IPL [Member] |
Jointly-Owned Electric Utility Plant | JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0% |  | $632 |  | $264 |  | $7
George Neal Unit 4 | 25.7% |  | 196 |  | 107 |  | 6
George Neal Unit 3 | 28.0% |  | 181 |  | 85 |  | 8
Louisa Unit 1 | 4.0% |  | 44 |  | 22 |  | —
|  |  | 1,053 |  | 478 |  | 21
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 53.5% |  | 818 |  | 361 |  | 6
West Riverside Energy Center and Solar Facility (a) | 73.8% |  | 581 |  | 60 |  | 6
Forward Wind Energy Center | 42.6% |  | 118 |  | 53 |  | —
|  |  | 1,517 |  | 474 |  | 12
Alliant Energy |  |  | $2,570 |  | $952 |  | $33
(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.
WPL [Member] |
Jointly-Owned Electric Utility Plant | JOINTLY-OWNED ELECTRIC UTILITY PLANT Under joint ownership agreements with other utilities, IPL and WPL have undivided ownership interests in jointly-owned EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. IPL’s and WPL’s shares of expenses from jointly-owned EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in the income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned EGUs at December 31, 2023 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0% |  | $632 |  | $264 |  | $7
George Neal Unit 4 | 25.7% |  | 196 |  | 107 |  | 6
George Neal Unit 3 | 28.0% |  | 181 |  | 85 |  | 8
Louisa Unit 1 | 4.0% |  | 44 |  | 22 |  | —
|  |  | 1,053 |  | 478 |  | 21
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 53.5% |  | 818 |  | 361 |  | 6
West Riverside Energy Center and Solar Facility (a) | 73.8% |  | 581 |  | 60 |  | 6
Forward Wind Energy Center | 42.6% |  | 118 |  | 53 |  | —
|  |  | 1,517 |  | 474 |  | 12
Alliant Energy |  |  | $2,570 |  | $952 |  | $33
(a)In 2023, Madison Gas and Electric Company and WEC Energy Group, Inc. acquired partial ownership interests in West Riverside. The related proceeds are included in “Proceeds from sales of partial ownership interests in West Riverside” in investing activities in Alliant Energy’s and WPL’s cash flows statements in 2023.

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