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Jointly-Owned Electric Utility Plant | 12 Months Ended
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Dec. 31, 2017
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 coal-fired EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. KWh generation and operating expenses are primarily divided between the joint owners on the same basis as ownership. IPL’s and WPL’s shares of expenses from jointly-owned coal-fired EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in their income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2017 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0 | % |  |  | $501.8 |  |  |  | $144.9 |  |  |  | $37.3 |
George Neal Unit 4 | 25.7 | % |  | 187.2 |  |  | 85.2 |  |  | 0.8 |
George Neal Unit 3 | 28.0 | % |  | 150.6 |  |  | 53.0 |  |  | 2.5 |
Louisa Unit 1 | 4.0 | % |  | 37.8 |  |  | 22.4 |  |  | 1.4 |
|  |  | 877.4 |  |  | 305.5 |  |  | 42.0 |
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 50.1 | % |  | 714.7 |  |  | 216.8 |  |  | 46.9 |
Edgewater Unit 4 | 68.2 | % |  | 99.9 |  |  | 60.4 |  |  | 0.1 |
|  |  | 814.6 |  |  | 277.2 |  |  | 47.0 |
Alliant Energy |  |  |  | $1,692.0 |  |  |  | $582.7 |  |  |  | $89.0 |
In 2016, WPL received an order from the PSCW approving amendments to the Columbia joint operating agreement, which allow the co-owners to forgo certain capital expenditures at Columbia (excluding capital expenditures related to the Columbia Unit 2 SCR currently being constructed), resulting in WPL incurring these additional capital expenditures in exchange for a proportional increase in its ownership share of Columbia. Based on the additional capital expenditures WPL currently expects to incur through June 1, 2020, WPL’s ownership interest in Columbia is expected to increase in the future. In June 2017, FERC approved these amendments to the Columbia joint operating agreement. In October 2017, WPL received an order from the PSCW authorizing various electric cooperatives, which currently have wholesale power supply agreements with WPL, to acquire a partial ownership interest in West Riverside while the EGU is being constructed.
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 coal-fired EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. KWh generation and operating expenses are primarily divided between the joint owners on the same basis as ownership. IPL’s and WPL’s shares of expenses from jointly-owned coal-fired EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in their income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2017 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0 | % |  |  | $501.8 |  |  |  | $144.9 |  |  |  | $37.3 |
George Neal Unit 4 | 25.7 | % |  | 187.2 |  |  | 85.2 |  |  | 0.8 |
George Neal Unit 3 | 28.0 | % |  | 150.6 |  |  | 53.0 |  |  | 2.5 |
Louisa Unit 1 | 4.0 | % |  | 37.8 |  |  | 22.4 |  |  | 1.4 |
|  |  | 877.4 |  |  | 305.5 |  |  | 42.0 |
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 50.1 | % |  | 714.7 |  |  | 216.8 |  |  | 46.9 |
Edgewater Unit 4 | 68.2 | % |  | 99.9 |  |  | 60.4 |  |  | 0.1 |
|  |  | 814.6 |  |  | 277.2 |  |  | 47.0 |
Alliant Energy |  |  |  | $1,692.0 |  |  |  | $582.7 |  |  |  | $89.0 |
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 coal-fired EGUs. Each of the respective owners is responsible for the financing of its portion of the construction costs. KWh generation and operating expenses are primarily divided between the joint owners on the same basis as ownership. IPL’s and WPL’s shares of expenses from jointly-owned coal-fired EGUs are included in the corresponding operating expenses (e.g., electric production fuel, other operation and maintenance, etc.) in their income statements. Information relative to IPL’s and WPL’s ownership interest in these jointly-owned coal-fired EGUs at December 31, 2017 was as follows (dollars in millions):
| Ownership |  | Electric |  | Accumulated Provision |  | Construction
| Interest % |  | Plant |  | for Depreciation |  | Work in Progress
IPL |  |  |  |  |  |  |
Ottumwa Unit 1 | 48.0 | % |  |  | $501.8 |  |  |  | $144.9 |  |  |  | $37.3 |
George Neal Unit 4 | 25.7 | % |  | 187.2 |  |  | 85.2 |  |  | 0.8 |
George Neal Unit 3 | 28.0 | % |  | 150.6 |  |  | 53.0 |  |  | 2.5 |
Louisa Unit 1 | 4.0 | % |  | 37.8 |  |  | 22.4 |  |  | 1.4 |
|  |  | 877.4 |  |  | 305.5 |  |  | 42.0 |
WPL |  |  |  |  |  |  |
Columbia Units 1-2 | 50.1 | % |  | 714.7 |  |  | 216.8 |  |  | 46.9 |
Edgewater Unit 4 | 68.2 | % |  | 99.9 |  |  | 60.4 |  |  | 0.1 |
|  |  | 814.6 |  |  | 277.2 |  |  | 47.0 |
Alliant Energy |  |  |  | $1,692.0 |  |  |  | $582.7 |  |  |  | $89.0 |
In 2016, WPL received an order from the PSCW approving amendments to the Columbia joint operating agreement, which allow the co-owners to forgo certain capital expenditures at Columbia (excluding capital expenditures related to the Columbia Unit 2 SCR currently being constructed), resulting in WPL incurring these additional capital expenditures in exchange for a proportional increase in its ownership share of Columbia. Based on the additional capital expenditures WPL currently expects to incur through June 1, 2020, WPL’s ownership interest in Columbia is expected to increase in the future. In June 2017, FERC approved these amendments to the Columbia joint operating agreement. In October 2017, WPL received an order from the PSCW authorizing various electric cooperatives, which currently have wholesale power supply agreements with WPL, to acquire a partial ownership interest in West Riverside while the EGU is being constructed.

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