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Regulatory Matters | 6 Months Ended
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Jun. 30, 2020
Public Utilities, General Disclosures [Line Items] |
Regulatory Matters | REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019
Tax-related |  | $842.5 |  |  |  | $817.6 |  |  |  | $797.4 |  |  |  | $776.8 |  |  |  | $45.1 |  |  |  | $40.8 |
Pension and OPEB costs | 501.2 |  |  | 524.0 |  |  | 251.3 |  |  | 262.5 |  |  | 249.9 |  |  | 261.5 |
Assets retired early | 122.9 |  |  | 134.0 |  |  | 81.8 |  |  | 87.9 |  |  | 41.1 |  |  | 46.1 |
Asset retirement obligations | 114.0 |  |  | 111.8 |  |  | 78.2 |  |  | 76.2 |  |  | 35.8 |  |  | 35.6 |
IPL’s DAEC PPA amendment | 109.4 |  |  | 108.2 |  |  | 109.4 |  |  | 108.2 |  |  | — |  |  | — |
Derivatives | 47.0 |  |  | 39.5 |  |  | 20.5 |  |  | 18.3 |  |  | 26.5 |  |  | 21.2 |
Emission allowances | 19.8 |  |  | 21.1 |  |  | 19.8 |  |  | 21.1 |  |  | — |  |  | — |
Other | 86.2 |  |  | 88.5 |  |  | 46.5 |  |  | 48.3 |  |  | 39.7 |  |  | 40.2 |
|  | $1,843.0 |  |  |  | $1,844.7 |  |  |  | $1,404.9 |  |  |  | $1,399.3 |  |  |  | $438.1 |  |  |  | $445.4 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019
Tax-related |  | $779.0 |  |  |  | $835.6 |  |  |  | $343.6 |  |  |  | $350.9 |  |  |  | $435.4 |  |  |  | $484.7 |
Cost of removal obligations | 385.8 |  |  | 387.7 |  |  | 256.4 |  |  | 257.0 |  |  | 129.4 |  |  | 130.7 |
Electric transmission cost recovery | 66.3 |  |  | 88.6 |  |  | 30.7 |  |  | 51.3 |  |  | 35.6 |  |  | 37.3 |
Commodity cost recovery | 30.1 |  |  | 24.2 |  |  | 14.0 |  |  | 8.8 |  |  | 16.1 |  |  | 15.4 |
Derivatives | 28.8 |  |  | 19.9 |  |  | 26.3 |  |  | 17.4 |  |  | 2.5 |  |  | 2.5 |
WPL’s earnings sharing mechanism | 20.4 |  |  | 21.9 |  |  | — |  |  | — |  |  | 20.4 |  |  | 21.9 |
Other | 60.6 |  |  | 45.7 |  |  | 46.9 |  |  | 29.3 |  |  | 13.7 |  |  | 16.4 |
|  | $1,371.0 |  |  |  | $1,423.6 |  |  |  | $717.9 |  |  |  | $714.7 |  |  |  | $653.1 |  |  |  | $708.9 |
Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform. During the six months ended June 30, 2020, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities decreased primarily from returning a portion of these excess deferred tax benefits back to customers. Electric transmission cost recovery - In the second quarter of 2020, pursuant to a June 2020 IUB order, IPL issued $42 million of credits to its retail electric customers through its transmission cost rider for amounts previously collected in rates, which resulted in a corresponding reduction to “Electric transmission service” expense in Alliant Energy’s and IPL’s income statements for the three and six months ended June 30, 2020. Refer to Note 13(f) for discussion of refunds received by IPL and WPL in the second quarter of 2020 related to MISO transmission owner return on equity complaints.
IPL [Member] |
Public Utilities, General Disclosures [Line Items] |
Regulatory Matters | REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019
Tax-related |  | $842.5 |  |  |  | $817.6 |  |  |  | $797.4 |  |  |  | $776.8 |  |  |  | $45.1 |  |  |  | $40.8 |
Pension and OPEB costs | 501.2 |  |  | 524.0 |  |  | 251.3 |  |  | 262.5 |  |  | 249.9 |  |  | 261.5 |
Assets retired early | 122.9 |  |  | 134.0 |  |  | 81.8 |  |  | 87.9 |  |  | 41.1 |  |  | 46.1 |
Asset retirement obligations | 114.0 |  |  | 111.8 |  |  | 78.2 |  |  | 76.2 |  |  | 35.8 |  |  | 35.6 |
IPL’s DAEC PPA amendment | 109.4 |  |  | 108.2 |  |  | 109.4 |  |  | 108.2 |  |  | — |  |  | — |
Derivatives | 47.0 |  |  | 39.5 |  |  | 20.5 |  |  | 18.3 |  |  | 26.5 |  |  | 21.2 |
Emission allowances | 19.8 |  |  | 21.1 |  |  | 19.8 |  |  | 21.1 |  |  | — |  |  | — |
Other | 86.2 |  |  | 88.5 |  |  | 46.5 |  |  | 48.3 |  |  | 39.7 |  |  | 40.2 |
|  | $1,843.0 |  |  |  | $1,844.7 |  |  |  | $1,404.9 |  |  |  | $1,399.3 |  |  |  | $438.1 |  |  |  | $445.4 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019
Tax-related |  | $779.0 |  |  |  | $835.6 |  |  |  | $343.6 |  |  |  | $350.9 |  |  |  | $435.4 |  |  |  | $484.7 |
Cost of removal obligations | 385.8 |  |  | 387.7 |  |  | 256.4 |  |  | 257.0 |  |  | 129.4 |  |  | 130.7 |
Electric transmission cost recovery | 66.3 |  |  | 88.6 |  |  | 30.7 |  |  | 51.3 |  |  | 35.6 |  |  | 37.3 |
Commodity cost recovery | 30.1 |  |  | 24.2 |  |  | 14.0 |  |  | 8.8 |  |  | 16.1 |  |  | 15.4 |
Derivatives | 28.8 |  |  | 19.9 |  |  | 26.3 |  |  | 17.4 |  |  | 2.5 |  |  | 2.5 |
WPL’s earnings sharing mechanism | 20.4 |  |  | 21.9 |  |  | — |  |  | — |  |  | 20.4 |  |  | 21.9 |
Other | 60.6 |  |  | 45.7 |  |  | 46.9 |  |  | 29.3 |  |  | 13.7 |  |  | 16.4 |
|  | $1,371.0 |  |  |  | $1,423.6 |  |  |  | $717.9 |  |  |  | $714.7 |  |  |  | $653.1 |  |  |  | $708.9 |
Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform. During the six months ended June 30, 2020, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities decreased primarily from returning a portion of these excess deferred tax benefits back to customers. Electric transmission cost recovery - In the second quarter of 2020, pursuant to a June 2020 IUB order, IPL issued $42 million of credits to its retail electric customers through its transmission cost rider for amounts previously collected in rates, which resulted in a corresponding reduction to “Electric transmission service” expense in Alliant Energy’s and IPL’s income statements for the three and six months ended June 30, 2020. Refer to Note 13(f) for discussion of refunds received by IPL and WPL in the second quarter of 2020 related to MISO transmission owner return on equity complaints.
WPL [Member] |
Public Utilities, General Disclosures [Line Items] |
Regulatory Matters | REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019
Tax-related |  | $842.5 |  |  |  | $817.6 |  |  |  | $797.4 |  |  |  | $776.8 |  |  |  | $45.1 |  |  |  | $40.8 |
Pension and OPEB costs | 501.2 |  |  | 524.0 |  |  | 251.3 |  |  | 262.5 |  |  | 249.9 |  |  | 261.5 |
Assets retired early | 122.9 |  |  | 134.0 |  |  | 81.8 |  |  | 87.9 |  |  | 41.1 |  |  | 46.1 |
Asset retirement obligations | 114.0 |  |  | 111.8 |  |  | 78.2 |  |  | 76.2 |  |  | 35.8 |  |  | 35.6 |
IPL’s DAEC PPA amendment | 109.4 |  |  | 108.2 |  |  | 109.4 |  |  | 108.2 |  |  | — |  |  | — |
Derivatives | 47.0 |  |  | 39.5 |  |  | 20.5 |  |  | 18.3 |  |  | 26.5 |  |  | 21.2 |
Emission allowances | 19.8 |  |  | 21.1 |  |  | 19.8 |  |  | 21.1 |  |  | — |  |  | — |
Other | 86.2 |  |  | 88.5 |  |  | 46.5 |  |  | 48.3 |  |  | 39.7 |  |  | 40.2 |
|  | $1,843.0 |  |  |  | $1,844.7 |  |  |  | $1,404.9 |  |  |  | $1,399.3 |  |  |  | $438.1 |  |  |  | $445.4 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019 |  | June 30, 2020 |  | December 31, 2019
Tax-related |  | $779.0 |  |  |  | $835.6 |  |  |  | $343.6 |  |  |  | $350.9 |  |  |  | $435.4 |  |  |  | $484.7 |
Cost of removal obligations | 385.8 |  |  | 387.7 |  |  | 256.4 |  |  | 257.0 |  |  | 129.4 |  |  | 130.7 |
Electric transmission cost recovery | 66.3 |  |  | 88.6 |  |  | 30.7 |  |  | 51.3 |  |  | 35.6 |  |  | 37.3 |
Commodity cost recovery | 30.1 |  |  | 24.2 |  |  | 14.0 |  |  | 8.8 |  |  | 16.1 |  |  | 15.4 |
Derivatives | 28.8 |  |  | 19.9 |  |  | 26.3 |  |  | 17.4 |  |  | 2.5 |  |  | 2.5 |
WPL’s earnings sharing mechanism | 20.4 |  |  | 21.9 |  |  | — |  |  | — |  |  | 20.4 |  |  | 21.9 |
Other | 60.6 |  |  | 45.7 |  |  | 46.9 |  |  | 29.3 |  |  | 13.7 |  |  | 16.4 |
|  | $1,371.0 |  |  |  | $1,423.6 |  |  |  | $717.9 |  |  |  | $714.7 |  |  |  | $653.1 |  |  |  | $708.9 |
Tax-related - Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities are primarily related to excess deferred tax benefits resulting from the remeasurement of accumulated deferred income taxes caused by Federal Tax Reform. During the six months ended June 30, 2020, Alliant Energy’s, IPL’s and WPL’s tax-related regulatory liabilities decreased primarily from returning a portion of these excess deferred tax benefits back to customers. Electric transmission cost recovery - In the second quarter of 2020, pursuant to a June 2020 IUB order, IPL issued $42 million of credits to its retail electric customers through its transmission cost rider for amounts previously collected in rates, which resulted in a corresponding reduction to “Electric transmission service” expense in Alliant Energy’s and IPL’s income statements for the three and six months ended June 30, 2020. Refer to Note 13(f) for discussion of refunds received by IPL and WPL in the second quarter of 2020 related to MISO transmission owner return on equity complaints.

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