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Property, Plant and Equipment (Tables) | 12 Months Ended
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Dec. 31, 2019
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service |  | $7,625.3 |  |  |  | $6,800.6 |  |  |  | $4,432.4 |  |  |  | $3,610.4 |  |  |  | $3,192.9 |  |  |  | $3,190.2 |
Distribution in service | 5,783.3 |  |  | 5,452.2 |  |  | 3,190.0 |  |  | 3,023.7 |  |  | 2,593.3 |  |  | 2,428.5 |
Other in service | 456.0 |  |  | 410.8 |  |  | 298.6 |  |  | 260.4 |  |  | 157.4 |  |  | 150.4 |
Total electric plant | 13,864.6 |  |  | 12,663.6 |  |  | 7,921.0 |  |  | 6,894.5 |  |  | 5,943.6 |  |  | 5,769.1 |
Gas plant in service | 1,462.7 |  |  | 1,387.6 |  |  | 801.5 |  |  | 763.1 |  |  | 661.2 |  |  | 624.5 |
Other plant in service | 519.7 |  |  | 513.2 |  |  | 344.7 |  |  | 322.4 |  |  | 175.0 |  |  | 190.8 |
Accumulated depreciation | (4,601.4 | ) |  | (4,314.6 | ) |  | (2,498.3 | ) |  | (2,294.7 | ) |  | (2,103.1 | ) |  | (2,019.9 | )
Net plant | 11,245.6 |  |  | 10,249.8 |  |  | 6,568.9 |  |  | 5,685.3 |  |  | 4,676.7 |  |  | 4,564.5 |
Leased Sheboygan Falls Energy Facility, net (a) | — |  |  | — |  |  | — |  |  | — |  |  | 32.3 |  |  | 38.1 |
Construction work in progress | 1,835.0 |  |  | 1,774.8 |  |  | 906.8 |  |  | 1,091.2 |  |  | 928.2 |  |  | 683.6 |
Other, net | 6.1 |  |  | 6.1 |  |  | 5.0 |  |  | 5.0 |  |  | 1.1 |  |  | 1.1 |
Total utility | 13,086.7 |  |  | 12,030.7 |  |  | 7,480.7 |  |  | 6,781.5 |  |  | 5,638.3 |  |  | 5,287.3 |
Non-utility and other: |  |  |  |  |  |  |  |  |  |  |
Non-utility Generation, net (b) | 82.9 |  |  | 86.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (c) | 357.5 |  |  | 344.8 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-utility and other | 440.4 |  |  | 431.7 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $13,527.1 |  |  |  | $12,462.4 |  |  |  | $7,480.7 |  |  |  | $6,781.5 |  |  |  | $5,638.3 |  |  |  | $5,287.3 |
(a) | Less accumulated amortization of $88.7 million and $82.8 million for WPL as of December 31, 2019 and 2018, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.
(b) | Less accumulated depreciation of $58.5 million and $54.5 million for Alliant Energy as of December 31, 2019 and 2018, respectively.
(c) Less accumulated depreciation of $172.4 million and $167.5 million for Alliant Energy as of December 31, 2019 and 2018, respectively.
Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2019 |  | 2018 |  | 2017 |  | 2019 |  | 2018 |  | 2017 |  | 2019 |  | 2018 |  | 2017
Equity |  | $65.5 |  |  |  | $51.4 |  |  |  | $33.6 |  |  |  | $35.2 |  |  |  | $28.6 |  |  |  | $21.1 |  |  |  | $30.3 |  |  |  | $22.8 |  |  |  | $12.5 |
Debt | 27.2 |  |  | 24.2 |  |  | 16.1 |  |  | 14.2 |  |  | 13.6 |  |  | 10.3 |  |  | 13.0 |  |  | 10.6 |  |  | 5.8 |
|  | $92.7 |  |  |  | $75.6 |  |  |  | $49.7 |  |  |  | $49.4 |  |  |  | $42.2 |  |  |  | $31.4 |  |  |  | $43.3 |  |  |  | $33.4 |  |  |  | $18.3 |
IPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service |  | $7,625.3 |  |  |  | $6,800.6 |  |  |  | $4,432.4 |  |  |  | $3,610.4 |  |  |  | $3,192.9 |  |  |  | $3,190.2 |
Distribution in service | 5,783.3 |  |  | 5,452.2 |  |  | 3,190.0 |  |  | 3,023.7 |  |  | 2,593.3 |  |  | 2,428.5 |
Other in service | 456.0 |  |  | 410.8 |  |  | 298.6 |  |  | 260.4 |  |  | 157.4 |  |  | 150.4 |
Total electric plant | 13,864.6 |  |  | 12,663.6 |  |  | 7,921.0 |  |  | 6,894.5 |  |  | 5,943.6 |  |  | 5,769.1 |
Gas plant in service | 1,462.7 |  |  | 1,387.6 |  |  | 801.5 |  |  | 763.1 |  |  | 661.2 |  |  | 624.5 |
Other plant in service | 519.7 |  |  | 513.2 |  |  | 344.7 |  |  | 322.4 |  |  | 175.0 |  |  | 190.8 |
Accumulated depreciation | (4,601.4 | ) |  | (4,314.6 | ) |  | (2,498.3 | ) |  | (2,294.7 | ) |  | (2,103.1 | ) |  | (2,019.9 | )
Net plant | 11,245.6 |  |  | 10,249.8 |  |  | 6,568.9 |  |  | 5,685.3 |  |  | 4,676.7 |  |  | 4,564.5 |
Leased Sheboygan Falls Energy Facility, net (a) | — |  |  | — |  |  | — |  |  | — |  |  | 32.3 |  |  | 38.1 |
Construction work in progress | 1,835.0 |  |  | 1,774.8 |  |  | 906.8 |  |  | 1,091.2 |  |  | 928.2 |  |  | 683.6 |
Other, net | 6.1 |  |  | 6.1 |  |  | 5.0 |  |  | 5.0 |  |  | 1.1 |  |  | 1.1 |
Total utility | 13,086.7 |  |  | 12,030.7 |  |  | 7,480.7 |  |  | 6,781.5 |  |  | 5,638.3 |  |  | 5,287.3 |
Non-utility and other: |  |  |  |  |  |  |  |  |  |  |
Non-utility Generation, net (b) | 82.9 |  |  | 86.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (c) | 357.5 |  |  | 344.8 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-utility and other | 440.4 |  |  | 431.7 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $13,527.1 |  |  |  | $12,462.4 |  |  |  | $7,480.7 |  |  |  | $6,781.5 |  |  |  | $5,638.3 |  |  |  | $5,287.3 |
(a) | Less accumulated amortization of $88.7 million and $82.8 million for WPL as of December 31, 2019 and 2018, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.
(b) | Less accumulated depreciation of $58.5 million and $54.5 million for Alliant Energy as of December 31, 2019 and 2018, respectively.
(c) Less accumulated depreciation of $172.4 million and $167.5 million for Alliant Energy as of December 31, 2019 and 2018, respectively.
Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2019 |  | 2018 |  | 2017 |  | 2019 |  | 2018 |  | 2017 |  | 2019 |  | 2018 |  | 2017
Equity |  | $65.5 |  |  |  | $51.4 |  |  |  | $33.6 |  |  |  | $35.2 |  |  |  | $28.6 |  |  |  | $21.1 |  |  |  | $30.3 |  |  |  | $22.8 |  |  |  | $12.5 |
Debt | 27.2 |  |  | 24.2 |  |  | 16.1 |  |  | 14.2 |  |  | 13.6 |  |  | 10.3 |  |  | 13.0 |  |  | 10.6 |  |  | 5.8 |
|  | $92.7 |  |  |  | $75.6 |  |  |  | $49.7 |  |  |  | $49.4 |  |  |  | $42.2 |  |  |  | $31.4 |  |  |  | $43.3 |  |  |  | $33.4 |  |  |  | $18.3 |
WPL [Member] |
Property, Plant and Equipment [Line Items] |
Property, Plant and Equipment | At December 31, details of property, plant and equipment on the balance sheets were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2019 |  | 2018 |  | 2019 |  | 2018 |  | 2019 |  | 2018
Utility: |  |  |  |  |  |  |  |  |  |  |
Electric plant: |  |  |  |  |  |  |  |  |  |  |
Generation in service |  | $7,625.3 |  |  |  | $6,800.6 |  |  |  | $4,432.4 |  |  |  | $3,610.4 |  |  |  | $3,192.9 |  |  |  | $3,190.2 |
Distribution in service | 5,783.3 |  |  | 5,452.2 |  |  | 3,190.0 |  |  | 3,023.7 |  |  | 2,593.3 |  |  | 2,428.5 |
Other in service | 456.0 |  |  | 410.8 |  |  | 298.6 |  |  | 260.4 |  |  | 157.4 |  |  | 150.4 |
Total electric plant | 13,864.6 |  |  | 12,663.6 |  |  | 7,921.0 |  |  | 6,894.5 |  |  | 5,943.6 |  |  | 5,769.1 |
Gas plant in service | 1,462.7 |  |  | 1,387.6 |  |  | 801.5 |  |  | 763.1 |  |  | 661.2 |  |  | 624.5 |
Other plant in service | 519.7 |  |  | 513.2 |  |  | 344.7 |  |  | 322.4 |  |  | 175.0 |  |  | 190.8 |
Accumulated depreciation | (4,601.4 | ) |  | (4,314.6 | ) |  | (2,498.3 | ) |  | (2,294.7 | ) |  | (2,103.1 | ) |  | (2,019.9 | )
Net plant | 11,245.6 |  |  | 10,249.8 |  |  | 6,568.9 |  |  | 5,685.3 |  |  | 4,676.7 |  |  | 4,564.5 |
Leased Sheboygan Falls Energy Facility, net (a) | — |  |  | — |  |  | — |  |  | — |  |  | 32.3 |  |  | 38.1 |
Construction work in progress | 1,835.0 |  |  | 1,774.8 |  |  | 906.8 |  |  | 1,091.2 |  |  | 928.2 |  |  | 683.6 |
Other, net | 6.1 |  |  | 6.1 |  |  | 5.0 |  |  | 5.0 |  |  | 1.1 |  |  | 1.1 |
Total utility | 13,086.7 |  |  | 12,030.7 |  |  | 7,480.7 |  |  | 6,781.5 |  |  | 5,638.3 |  |  | 5,287.3 |
Non-utility and other: |  |  |  |  |  |  |  |  |  |  |
Non-utility Generation, net (b) | 82.9 |  |  | 86.9 |  |  | — |  |  | — |  |  | — |  |  | — |
Corporate Services and other, net (c) | 357.5 |  |  | 344.8 |  |  | — |  |  | — |  |  | — |  |  | — |
Total non-utility and other | 440.4 |  |  | 431.7 |  |  | — |  |  | — |  |  | — |  |  | — |
Total property, plant and equipment |  | $13,527.1 |  |  |  | $12,462.4 |  |  |  | $7,480.7 |  |  |  | $6,781.5 |  |  |  | $5,638.3 |  |  |  | $5,287.3 |
(a) | Less accumulated amortization of $88.7 million and $82.8 million for WPL as of December 31, 2019 and 2018, respectively. The Sheboygan Falls Energy Facility is eliminated from WPL upon consolidation and is included in the “Non-utility Generation, net” line within Alliant Energy’s consolidated property, plant and equipment.
(b) | Less accumulated depreciation of $58.5 million and $54.5 million for Alliant Energy as of December 31, 2019 and 2018, respectively.
(c) Less accumulated depreciation of $172.4 million and $167.5 million for Alliant Energy as of December 31, 2019 and 2018, respectively.
Allowance For Funds Used During Construction | The amount of AFUDC generated by equity and debt components was as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
| 2019 |  | 2018 |  | 2017 |  | 2019 |  | 2018 |  | 2017 |  | 2019 |  | 2018 |  | 2017
Equity |  | $65.5 |  |  |  | $51.4 |  |  |  | $33.6 |  |  |  | $35.2 |  |  |  | $28.6 |  |  |  | $21.1 |  |  |  | $30.3 |  |  |  | $22.8 |  |  |  | $12.5 |
Debt | 27.2 |  |  | 24.2 |  |  | 16.1 |  |  | 14.2 |  |  | 13.6 |  |  | 10.3 |  |  | 13.0 |  |  | 10.6 |  |  | 5.8 |
|  | $92.7 |  |  |  | $75.6 |  |  |  | $49.7 |  |  |  | $49.4 |  |  |  | $42.2 |  |  |  | $31.4 |  |  |  | $43.3 |  |  |  | $33.4 |  |  |  | $18.3 |

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