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Regulatory Matters | 3 Months Ended
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Mar. 31, 2019
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
| March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018
Tax-related |  | $802.9 |  |  |  | $820.6 |  |  |  | $770.2 |  |  |  | $783.1 |  |  |  | $32.7 |  |  |  | $37.5 |
Pension and OPEB costs | 532.6 |  |  | 542.3 |  |  | 269.3 |  |  | 274.0 |  |  | 263.3 |  |  | 268.3 |
Asset retirement obligations | 112.1 |  |  | 110.8 |  |  | 77.5 |  |  | 76.3 |  |  | 34.6 |  |  | 34.5 |
EGUs retired early | 107.3 |  |  | 111.6 |  |  | 53.6 |  |  | 55.4 |  |  | 53.7 |  |  | 56.2 |
IPL’s DAEC PPA amendment | 106.5 |  |  | — |  |  | 106.5 |  |  | — |  |  | — |  |  | — |
Emission allowances | 23.0 |  |  | 23.6 |  |  | 23.0 |  |  | 23.6 |  |  | — |  |  | — |
Derivatives | 16.9 |  |  | 28.0 |  |  | 8.0 |  |  | 15.1 |  |  | 8.9 |  |  | 12.9 |
Other | 91.1 |  |  | 100.4 |  |  | 43.3 |  |  | 51.5 |  |  | 47.8 |  |  | 48.9 |
|  | $1,792.4 |  |  |  | $1,737.3 |  |  |  | $1,351.4 |  |  |  | $1,279.0 |  |  |  | $441.0 |  |  |  | $458.3 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018
Tax-related |  | $858.1 |  |  |  | $890.6 |  |  |  | $366.2 |  |  |  | $390.1 |  |  |  | $491.9 |  |  |  | $500.5 |
Cost of removal obligations | 402.7 |  |  | 401.2 |  |  | 273.4 |  |  | 273.3 |  |  | 129.3 |  |  | 127.9 |
Electric transmission cost recovery | 104.8 |  |  | 104.0 |  |  | 53.0 |  |  | 47.7 |  |  | 51.8 |  |  | 56.3 |
Commodity cost recovery | 43.2 |  |  | 16.8 |  |  | 32.2 |  |  | 11.9 |  |  | 11.0 |  |  | 4.9 |
WPL’s earnings sharing mechanism | 25.0 |  |  | 25.4 |  |  | — |  |  | — |  |  | 25.0 |  |  | 25.4 |
Other | 48.6 |  |  | 55.2 |  |  | 24.0 |  |  | 31.9 |  |  | 24.6 |  |  | 23.3 |
|  | $1,482.4 |  |  |  | $1,493.2 |  |  |  | $748.8 |  |  |  | $754.9 |  |  |  | $733.6 |  |  |  | $738.3 |
IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by five years. The IUB approved recovery of the buyout payment from IPL’s retail customers over a five-year period following the payment. The offsetting obligation has been discounted and is recorded in “Other liabilities” on Alliant Energy’s and IPL’s balance sheets. Utility Rate Reviews IPL’s Retail Electric Rate Review (2020 Forward Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers by $204 million, based on a 2020 forward-looking Test Period. IPL currently expects the proposed retail electric base rate increase to be largely offset by cost reductions in non-base rate factors, including lower electric transmission, fuel-related and energy efficiency costs. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric rate base increase of $90 million, on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision. Interveners have challenged, among other issues, the return on common equity percentage used in interim rates, and IPL expects that the IUB will address this issue in its final decision. The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision from the IUB in the fourth quarter of 2019 on the interim rate increase, as well as the remaining $114 million of final rates, which would be effective in the first quarter of 2020. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL’s Retail Gas Rate Review (2020 Forward Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers by $21 million, based on a 2020 forward-looking Test Period. IPL currently expects the proposed retail gas base rate increase will be more than offset by cost reductions in non-base rate factors, including lower cost of gas sold and energy efficiency costs. The key drivers for IPL’s request included recovery of capital projects. IPL currently expects a decision from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.
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
| March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018
Tax-related |  | $802.9 |  |  |  | $820.6 |  |  |  | $770.2 |  |  |  | $783.1 |  |  |  | $32.7 |  |  |  | $37.5 |
Pension and OPEB costs | 532.6 |  |  | 542.3 |  |  | 269.3 |  |  | 274.0 |  |  | 263.3 |  |  | 268.3 |
Asset retirement obligations | 112.1 |  |  | 110.8 |  |  | 77.5 |  |  | 76.3 |  |  | 34.6 |  |  | 34.5 |
EGUs retired early | 107.3 |  |  | 111.6 |  |  | 53.6 |  |  | 55.4 |  |  | 53.7 |  |  | 56.2 |
IPL’s DAEC PPA amendment | 106.5 |  |  | — |  |  | 106.5 |  |  | — |  |  | — |  |  | — |
Emission allowances | 23.0 |  |  | 23.6 |  |  | 23.0 |  |  | 23.6 |  |  | — |  |  | — |
Derivatives | 16.9 |  |  | 28.0 |  |  | 8.0 |  |  | 15.1 |  |  | 8.9 |  |  | 12.9 |
Other | 91.1 |  |  | 100.4 |  |  | 43.3 |  |  | 51.5 |  |  | 47.8 |  |  | 48.9 |
|  | $1,792.4 |  |  |  | $1,737.3 |  |  |  | $1,351.4 |  |  |  | $1,279.0 |  |  |  | $441.0 |  |  |  | $458.3 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018
Tax-related |  | $858.1 |  |  |  | $890.6 |  |  |  | $366.2 |  |  |  | $390.1 |  |  |  | $491.9 |  |  |  | $500.5 |
Cost of removal obligations | 402.7 |  |  | 401.2 |  |  | 273.4 |  |  | 273.3 |  |  | 129.3 |  |  | 127.9 |
Electric transmission cost recovery | 104.8 |  |  | 104.0 |  |  | 53.0 |  |  | 47.7 |  |  | 51.8 |  |  | 56.3 |
Commodity cost recovery | 43.2 |  |  | 16.8 |  |  | 32.2 |  |  | 11.9 |  |  | 11.0 |  |  | 4.9 |
WPL’s earnings sharing mechanism | 25.0 |  |  | 25.4 |  |  | — |  |  | — |  |  | 25.0 |  |  | 25.4 |
Other | 48.6 |  |  | 55.2 |  |  | 24.0 |  |  | 31.9 |  |  | 24.6 |  |  | 23.3 |
|  | $1,482.4 |  |  |  | $1,493.2 |  |  |  | $748.8 |  |  |  | $754.9 |  |  |  | $733.6 |  |  |  | $738.3 |
IPL’s DAEC PPA Amendment - In January 2019, IPL incurred an obligation to make a September 2020 buyout payment of $110 million in exchange for shortening the term of IPL’s DAEC nuclear generation PPA by five years. The IUB approved recovery of the buyout payment from IPL’s retail customers over a five-year period following the payment. The offsetting obligation has been discounted and is recorded in “Other liabilities” on Alliant Energy’s and IPL’s balance sheets. Utility Rate Reviews IPL’s Retail Electric Rate Review (2020 Forward Test Period) - In March 2019, IPL filed a request with the IUB to increase annual electric base rates for its Iowa retail electric customers by $204 million, based on a 2020 forward-looking Test Period. IPL currently expects the proposed retail electric base rate increase to be largely offset by cost reductions in non-base rate factors, including lower electric transmission, fuel-related and energy efficiency costs. IPL concurrently filed for interim retail electric rates based on 2018 historical data as adjusted for certain known and measurable changes occurring in the first quarter of 2019. An interim retail electric rate base increase of $90 million, on an annual basis, was implemented effective April 1, 2019. Implementing interim rates does not require regulatory approval; however, interim rates are subject to refund pending the IUB’s final rate review decision. Interveners have challenged, among other issues, the return on common equity percentage used in interim rates, and IPL expects that the IUB will address this issue in its final decision. The IUB generally must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed. IPL currently expects a final decision from the IUB in the fourth quarter of 2019 on the interim rate increase, as well as the remaining $114 million of final rates, which would be effective in the first quarter of 2020. The key drivers for IPL’s request included recovery of capital projects, including new wind generation. IPL’s Retail Gas Rate Review (2020 Forward Test Period) - In March 2019, IPL filed a request with the IUB to increase annual gas base rates for its Iowa retail gas customers by $21 million, based on a 2020 forward-looking Test Period. IPL currently expects the proposed retail gas base rate increase will be more than offset by cost reductions in non-base rate factors, including lower cost of gas sold and energy efficiency costs. The key drivers for IPL’s request included recovery of capital projects. IPL currently expects a decision from the IUB in the fourth quarter of 2019 with final rates effective in the first quarter of 2020.
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
| March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018
Tax-related |  | $802.9 |  |  |  | $820.6 |  |  |  | $770.2 |  |  |  | $783.1 |  |  |  | $32.7 |  |  |  | $37.5 |
Pension and OPEB costs | 532.6 |  |  | 542.3 |  |  | 269.3 |  |  | 274.0 |  |  | 263.3 |  |  | 268.3 |
Asset retirement obligations | 112.1 |  |  | 110.8 |  |  | 77.5 |  |  | 76.3 |  |  | 34.6 |  |  | 34.5 |
EGUs retired early | 107.3 |  |  | 111.6 |  |  | 53.6 |  |  | 55.4 |  |  | 53.7 |  |  | 56.2 |
IPL’s DAEC PPA amendment | 106.5 |  |  | — |  |  | 106.5 |  |  | — |  |  | — |  |  | — |
Emission allowances | 23.0 |  |  | 23.6 |  |  | 23.0 |  |  | 23.6 |  |  | — |  |  | — |
Derivatives | 16.9 |  |  | 28.0 |  |  | 8.0 |  |  | 15.1 |  |  | 8.9 |  |  | 12.9 |
Other | 91.1 |  |  | 100.4 |  |  | 43.3 |  |  | 51.5 |  |  | 47.8 |  |  | 48.9 |
|  | $1,792.4 |  |  |  | $1,737.3 |  |  |  | $1,351.4 |  |  |  | $1,279.0 |  |  |  | $441.0 |  |  |  | $458.3 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018 |  | March 31, 2019 |  | December 31, 2018
Tax-related |  | $858.1 |  |  |  | $890.6 |  |  |  | $366.2 |  |  |  | $390.1 |  |  |  | $491.9 |  |  |  | $500.5 |
Cost of removal obligations | 402.7 |  |  | 401.2 |  |  | 273.4 |  |  | 273.3 |  |  | 129.3 |  |  | 127.9 |
Electric transmission cost recovery | 104.8 |  |  | 104.0 |  |  | 53.0 |  |  | 47.7 |  |  | 51.8 |  |  | 56.3 |
Commodity cost recovery | 43.2 |  |  | 16.8 |  |  | 32.2 |  |  | 11.9 |  |  | 11.0 |  |  | 4.9 |
WPL’s earnings sharing mechanism | 25.0 |  |  | 25.4 |  |  | — |  |  | — |  |  | 25.0 |  |  | 25.4 |
Other | 48.6 |  |  | 55.2 |  |  | 24.0 |  |  | 31.9 |  |  | 24.6 |  |  | 23.3 |
|  | $1,482.4 |  |  |  | $1,493.2 |  |  |  | $748.8 |  |  |  | $754.9 |  |  |  | $733.6 |  |  |  | $738.3 |

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