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Regulatory Matters | 9 Months Ended
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Sep. 30, 2015
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
| September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014
Tax-related |  | $976.5 |  |  |  | $955.3 |  |  |  | $947.3 |  |  |  | $928.0 |  |  |  | $29.2 |  |  |  | $27.3 |
Pension and OPEB costs | 548.4 |  |  | 570.2 |  |  | 278.6 |  |  | 287.9 |  |  | 269.8 |  |  | 282.3 |
AROs | 81.8 |  |  | 73.7 |  |  | 47.6 |  |  | 41.4 |  |  | 34.2 |  |  | 32.3 |
Derivatives | 68.4 |  |  | 46.9 |  |  | 29.3 |  |  | 28.0 |  |  | 39.1 |  |  | 18.9 |
Commodity cost recovery | 33.2 |  |  | 31.1 |  |  | 1.2 |  |  | 0.4 |  |  | 32.0 |  |  | 30.7 |
Emission allowances | 26.5 |  |  | 27.4 |  |  | 26.5 |  |  | 27.4 |  |  | — |  |  | — |
Other | 73.1 |  |  | 79.1 |  |  | 39.7 |  |  | 44.8 |  |  | 33.4 |  |  | 34.3 |
|  | $1,807.9 |  |  |  | $1,783.7 |  |  |  | $1,370.2 |  |  |  | $1,357.9 |  |  |  | $437.7 |  |  |  | $425.8 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014
Cost of removal obligations |  | $406.2 |  |  |  | $421.7 |  |  |  | $261.3 |  |  |  | $279.1 |  |  |  | $144.9 |  |  |  | $142.6 |
IPL’s tax benefit riders | 179.5 |  |  | 243.0 |  |  | 179.5 |  |  | 243.0 |  |  | — |  |  | — |
Energy efficiency cost recovery | 53.0 |  |  | 64.3 |  |  | — |  |  | — |  |  | 53.0 |  |  | 64.3 |
Commodity cost recovery | 33.8 |  |  | 15.4 |  |  | 22.9 |  |  | 15.1 |  |  | 10.9 |  |  | 0.3 |
Electric transmission cost recovery | 31.4 |  |  | 19.4 |  |  | 15.8 |  |  | 19.4 |  |  | 15.6 |  |  | — |
Other | 40.2 |  |  | 57.4 |  |  | 23.0 |  |  | 26.9 |  |  | 17.2 |  |  | 30.5 |
|  | $744.1 |  |  |  | $821.2 |  |  |  | $502.5 |  |  |  | $583.5 |  |  |  | $241.6 |  |  |  | $237.7 |
Tax-related - Alliant Energy’s and IPL’s tax-related regulatory assets are generally impacted by certain property-related differences at IPL for which deferred tax is not recorded in the income statement pursuant to Iowa rate-making principles. Deferred tax amounts for such property-related differences at IPL are recorded to regulatory assets, along with the necessary revenue requirement tax gross-ups. During the nine months ended September 30, 2015, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due to property-related differences for qualifying repair expenditures. The July 2015 sale of IPL’s Minnesota electric distribution assets resulted in a reduction of certain tax-related regulatory assets on Alliant Energy’s and IPL’s balance sheets in 2015. Derivatives - Refer to Note 12 for discussion of derivative assets and derivative liabilities. IPL’s tax benefit riders - IPL’s tax benefit riders utilize regulatory liabilities to credit bills of IPL’s Iowa retail electric and gas customers to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs, allocation of insurance proceeds from floods in 2008, and cost of removal expenditures. For the nine months ended September 30, 2015, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by $64 million as follows (in millions):
Electric tax benefit rider credits |  | $55 |
Gas tax benefit rider credits | 9 |
|  | $64 |
Refer to Note 8 for additional details regarding IPL’s tax benefit riders. Electric transmission cost recovery - Electric revenues established in WPL’s retail electric rate case (2015/2016 Test Period) included recovery of expected increases in electric transmission service expense largely due to System Support Resource costs expected to be incurred. Due to a revision in MISO’s method to allocate System Support Resource costs, WPL no longer expects to incur certain System Support Resource costs. The difference between actual electric transmission service expense incurred and amounts collected from customers as electric revenues in 2015 are recorded as electric transmission service expense with an offsetting amount recorded to regulatory liabilities due to the escrow treatment authorized for WPL in its 2015/2016 Test Period retail electric rate case. Utility Rate Cases - IPL’s Iowa Retail Electric Rate Settlement Agreement - The IUB approved a settlement agreement in 2014 related to rates charged to IPL’s Iowa retail electric customers. The settlement agreement extends IPL’s Iowa retail electric base rates authorized in its 2009 Test Year rate case through 2016 and provides targeted retail electric customer billing credits beginning May 2014. For the three and nine months ended September 30, IPL recorded billing credits to reduce retail electric customers’ bills as follows (in millions):
| Three Months |  | Nine Months
| 2015 |  | 2014 |  | 2015 |  | 2014
Billing credits to reduce retail electric customers’ bills | $7 |  |  | $26 |  |  |  | $19 |  |  |  | $46 |
WPL’s Retail Fuel-related Rate Filing (2016 Test Year) - In July 2015, WPL filed a request with the PSCW to increase annual rates for WPL’s retail electric customers by $15 million, or approximately 1%, in 2016. The increase reflects anticipated increases in retail electric fuel-related costs in 2016. Any rate changes granted from this request are expected to be effective on January 1, 2016. WPL currently expects a decision from the PSCW regarding this rate filing by the end of 2015. WPL’s Retail Fuel-related Rate Filing (2015 Test Year) - Pursuant to a 2014 PSCW order, WPL’s 2015 fuel-related costs will be subject to deferral if they are outside an annual bandwidth of plus or minus 2% of the approved annual forecasted fuel-related costs. Retail fuel-related costs incurred by WPL through September 30, 2015 were lower than fuel-related costs used to determine rates for such period resulting in an over-collection of fuel-related costs. As of September 30, 2015, fuel-related costs outside of the approved range were $5 million and are included in “Commodity cost recovery” in Alliant Energy’s and WPL’s regulatory liabilities table above. WPL’s Retail Fuel-related Rate Filing (2014 Test Year) - Pursuant to a 2013 PSCW order, WPL’s 2014 fuel-related costs were subject to deferral since they were outside an annual bandwidth of plus or minus 2% of the approved annual forecasted fuel-related costs. Retail fuel-related costs incurred by WPL through December 31, 2014 were higher than fuel-related costs used to determine rates for such period resulting in an under-collection of fuel-related costs for 2014 of $33 million (including $28 million outside the approved range for 2014). The $28 million of deferred fuel-related costs is included in “Commodity cost recovery” in Alliant Energy’s and WPL’s regulatory assets table above. In July 2015, WPL received an order from the PSCW authorizing an annual retail electric rate increase of $28 million, or approximately 3%, effective January 1, 2016 to recover the 2014 Test Year deferred fuel-related costs.
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
| September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014
Tax-related |  | $976.5 |  |  |  | $955.3 |  |  |  | $947.3 |  |  |  | $928.0 |  |  |  | $29.2 |  |  |  | $27.3 |
Pension and OPEB costs | 548.4 |  |  | 570.2 |  |  | 278.6 |  |  | 287.9 |  |  | 269.8 |  |  | 282.3 |
AROs | 81.8 |  |  | 73.7 |  |  | 47.6 |  |  | 41.4 |  |  | 34.2 |  |  | 32.3 |
Derivatives | 68.4 |  |  | 46.9 |  |  | 29.3 |  |  | 28.0 |  |  | 39.1 |  |  | 18.9 |
Commodity cost recovery | 33.2 |  |  | 31.1 |  |  | 1.2 |  |  | 0.4 |  |  | 32.0 |  |  | 30.7 |
Emission allowances | 26.5 |  |  | 27.4 |  |  | 26.5 |  |  | 27.4 |  |  | — |  |  | — |
Other | 73.1 |  |  | 79.1 |  |  | 39.7 |  |  | 44.8 |  |  | 33.4 |  |  | 34.3 |
|  | $1,807.9 |  |  |  | $1,783.7 |  |  |  | $1,370.2 |  |  |  | $1,357.9 |  |  |  | $437.7 |  |  |  | $425.8 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014
Cost of removal obligations |  | $406.2 |  |  |  | $421.7 |  |  |  | $261.3 |  |  |  | $279.1 |  |  |  | $144.9 |  |  |  | $142.6 |
IPL’s tax benefit riders | 179.5 |  |  | 243.0 |  |  | 179.5 |  |  | 243.0 |  |  | — |  |  | — |
Energy efficiency cost recovery | 53.0 |  |  | 64.3 |  |  | — |  |  | — |  |  | 53.0 |  |  | 64.3 |
Commodity cost recovery | 33.8 |  |  | 15.4 |  |  | 22.9 |  |  | 15.1 |  |  | 10.9 |  |  | 0.3 |
Electric transmission cost recovery | 31.4 |  |  | 19.4 |  |  | 15.8 |  |  | 19.4 |  |  | 15.6 |  |  | — |
Other | 40.2 |  |  | 57.4 |  |  | 23.0 |  |  | 26.9 |  |  | 17.2 |  |  | 30.5 |
|  | $744.1 |  |  |  | $821.2 |  |  |  | $502.5 |  |  |  | $583.5 |  |  |  | $241.6 |  |  |  | $237.7 |
Tax-related - Alliant Energy’s and IPL’s tax-related regulatory assets are generally impacted by certain property-related differences at IPL for which deferred tax is not recorded in the income statement pursuant to Iowa rate-making principles. Deferred tax amounts for such property-related differences at IPL are recorded to regulatory assets, along with the necessary revenue requirement tax gross-ups. During the nine months ended September 30, 2015, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due to property-related differences for qualifying repair expenditures. The July 2015 sale of IPL’s Minnesota electric distribution assets resulted in a reduction of certain tax-related regulatory assets on Alliant Energy’s and IPL’s balance sheets in 2015. Derivatives - Refer to Note 12 for discussion of derivative assets and derivative liabilities. IPL’s tax benefit riders - IPL’s tax benefit riders utilize regulatory liabilities to credit bills of IPL’s Iowa retail electric and gas customers to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs, allocation of insurance proceeds from floods in 2008, and cost of removal expenditures. For the nine months ended September 30, 2015, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by $64 million as follows (in millions):
Electric tax benefit rider credits |  | $55 |
Gas tax benefit rider credits | 9 |
|  | $64 |
Refer to Note 8 for additional details regarding IPL’s tax benefit riders. Electric transmission cost recovery - Electric revenues established in WPL’s retail electric rate case (2015/2016 Test Period) included recovery of expected increases in electric transmission service expense largely due to System Support Resource costs expected to be incurred. Due to a revision in MISO’s method to allocate System Support Resource costs, WPL no longer expects to incur certain System Support Resource costs. The difference between actual electric transmission service expense incurred and amounts collected from customers as electric revenues in 2015 are recorded as electric transmission service expense with an offsetting amount recorded to regulatory liabilities due to the escrow treatment authorized for WPL in its 2015/2016 Test Period retail electric rate case. Utility Rate Cases - IPL’s Iowa Retail Electric Rate Settlement Agreement - The IUB approved a settlement agreement in 2014 related to rates charged to IPL’s Iowa retail electric customers. The settlement agreement extends IPL’s Iowa retail electric base rates authorized in its 2009 Test Year rate case through 2016 and provides targeted retail electric customer billing credits beginning May 2014. For the three and nine months ended September 30, IPL recorded billing credits to reduce retail electric customers’ bills as follows (in millions):
| Three Months |  | Nine Months
| 2015 |  | 2014 |  | 2015 |  | 2014
Billing credits to reduce retail electric customers’ bills | $7 |  |  | $26 |  |  |  | $19 |  |  |  | $46 |
WPL’s Retail Fuel-related Rate Filing (2016 Test Year) - In July 2015, WPL filed a request with the PSCW to increase annual rates for WPL’s retail electric customers by $15 million, or approximately 1%, in 2016. The increase reflects anticipated increases in retail electric fuel-related costs in 2016. Any rate changes granted from this request are expected to be effective on January 1, 2016. WPL currently expects a decision from the PSCW regarding this rate filing by the end of 2015. WPL’s Retail Fuel-related Rate Filing (2015 Test Year) - Pursuant to a 2014 PSCW order, WPL’s 2015 fuel-related costs will be subject to deferral if they are outside an annual bandwidth of plus or minus 2% of the approved annual forecasted fuel-related costs. Retail fuel-related costs incurred by WPL through September 30, 2015 were lower than fuel-related costs used to determine rates for such period resulting in an over-collection of fuel-related costs. As of September 30, 2015, fuel-related costs outside of the approved range were $5 million and are included in “Commodity cost recovery” in Alliant Energy’s and WPL’s regulatory liabilities table above. WPL’s Retail Fuel-related Rate Filing (2014 Test Year) - Pursuant to a 2013 PSCW order, WPL’s 2014 fuel-related costs were subject to deferral since they were outside an annual bandwidth of plus or minus 2% of the approved annual forecasted fuel-related costs. Retail fuel-related costs incurred by WPL through December 31, 2014 were higher than fuel-related costs used to determine rates for such period resulting in an under-collection of fuel-related costs for 2014 of $33 million (including $28 million outside the approved range for 2014). The $28 million of deferred fuel-related costs is included in “Commodity cost recovery” in Alliant Energy’s and WPL’s regulatory assets table above. In July 2015, WPL received an order from the PSCW authorizing an annual retail electric rate increase of $28 million, or approximately 3%, effective January 1, 2016 to recover the 2014 Test Year deferred fuel-related costs.
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
| September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014
Tax-related |  | $976.5 |  |  |  | $955.3 |  |  |  | $947.3 |  |  |  | $928.0 |  |  |  | $29.2 |  |  |  | $27.3 |
Pension and OPEB costs | 548.4 |  |  | 570.2 |  |  | 278.6 |  |  | 287.9 |  |  | 269.8 |  |  | 282.3 |
AROs | 81.8 |  |  | 73.7 |  |  | 47.6 |  |  | 41.4 |  |  | 34.2 |  |  | 32.3 |
Derivatives | 68.4 |  |  | 46.9 |  |  | 29.3 |  |  | 28.0 |  |  | 39.1 |  |  | 18.9 |
Commodity cost recovery | 33.2 |  |  | 31.1 |  |  | 1.2 |  |  | 0.4 |  |  | 32.0 |  |  | 30.7 |
Emission allowances | 26.5 |  |  | 27.4 |  |  | 26.5 |  |  | 27.4 |  |  | — |  |  | — |
Other | 73.1 |  |  | 79.1 |  |  | 39.7 |  |  | 44.8 |  |  | 33.4 |  |  | 34.3 |
|  | $1,807.9 |  |  |  | $1,783.7 |  |  |  | $1,370.2 |  |  |  | $1,357.9 |  |  |  | $437.7 |  |  |  | $425.8 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014 |  | September 30, 2015 |  | December 31, 2014
Cost of removal obligations |  | $406.2 |  |  |  | $421.7 |  |  |  | $261.3 |  |  |  | $279.1 |  |  |  | $144.9 |  |  |  | $142.6 |
IPL’s tax benefit riders | 179.5 |  |  | 243.0 |  |  | 179.5 |  |  | 243.0 |  |  | — |  |  | — |
Energy efficiency cost recovery | 53.0 |  |  | 64.3 |  |  | — |  |  | — |  |  | 53.0 |  |  | 64.3 |
Commodity cost recovery | 33.8 |  |  | 15.4 |  |  | 22.9 |  |  | 15.1 |  |  | 10.9 |  |  | 0.3 |
Electric transmission cost recovery | 31.4 |  |  | 19.4 |  |  | 15.8 |  |  | 19.4 |  |  | 15.6 |  |  | — |
Other | 40.2 |  |  | 57.4 |  |  | 23.0 |  |  | 26.9 |  |  | 17.2 |  |  | 30.5 |
|  | $744.1 |  |  |  | $821.2 |  |  |  | $502.5 |  |  |  | $583.5 |  |  |  | $241.6 |  |  |  | $237.7 |
Tax-related - Alliant Energy’s and IPL’s tax-related regulatory assets are generally impacted by certain property-related differences at IPL for which deferred tax is not recorded in the income statement pursuant to Iowa rate-making principles. Deferred tax amounts for such property-related differences at IPL are recorded to regulatory assets, along with the necessary revenue requirement tax gross-ups. During the nine months ended September 30, 2015, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due to property-related differences for qualifying repair expenditures. The July 2015 sale of IPL’s Minnesota electric distribution assets resulted in a reduction of certain tax-related regulatory assets on Alliant Energy’s and IPL’s balance sheets in 2015. Derivatives - Refer to Note 12 for discussion of derivative assets and derivative liabilities. IPL’s tax benefit riders - IPL’s tax benefit riders utilize regulatory liabilities to credit bills of IPL’s Iowa retail electric and gas customers to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs, allocation of insurance proceeds from floods in 2008, and cost of removal expenditures. For the nine months ended September 30, 2015, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by $64 million as follows (in millions):
Electric tax benefit rider credits |  | $55 |
Gas tax benefit rider credits | 9 |
|  | $64 |
Refer to Note 8 for additional details regarding IPL’s tax benefit riders. Electric transmission cost recovery - Electric revenues established in WPL’s retail electric rate case (2015/2016 Test Period) included recovery of expected increases in electric transmission service expense largely due to System Support Resource costs expected to be incurred. Due to a revision in MISO’s method to allocate System Support Resource costs, WPL no longer expects to incur certain System Support Resource costs. The difference between actual electric transmission service expense incurred and amounts collected from customers as electric revenues in 2015 are recorded as electric transmission service expense with an offsetting amount recorded to regulatory liabilities due to the escrow treatment authorized for WPL in its 2015/2016 Test Period retail electric rate case. Utility Rate Cases - IPL’s Iowa Retail Electric Rate Settlement Agreement - The IUB approved a settlement agreement in 2014 related to rates charged to IPL’s Iowa retail electric customers. The settlement agreement extends IPL’s Iowa retail electric base rates authorized in its 2009 Test Year rate case through 2016 and provides targeted retail electric customer billing credits beginning May 2014. For the three and nine months ended September 30, IPL recorded billing credits to reduce retail electric customers’ bills as follows (in millions):
| Three Months |  | Nine Months
| 2015 |  | 2014 |  | 2015 |  | 2014
Billing credits to reduce retail electric customers’ bills | $7 |  |  | $26 |  |  |  | $19 |  |  |  | $46 |
WPL’s Retail Fuel-related Rate Filing (2016 Test Year) - In July 2015, WPL filed a request with the PSCW to increase annual rates for WPL’s retail electric customers by $15 million, or approximately 1%, in 2016. The increase reflects anticipated increases in retail electric fuel-related costs in 2016. Any rate changes granted from this request are expected to be effective on January 1, 2016. WPL currently expects a decision from the PSCW regarding this rate filing by the end of 2015. WPL’s Retail Fuel-related Rate Filing (2015 Test Year) - Pursuant to a 2014 PSCW order, WPL’s 2015 fuel-related costs will be subject to deferral if they are outside an annual bandwidth of plus or minus 2% of the approved annual forecasted fuel-related costs. Retail fuel-related costs incurred by WPL through September 30, 2015 were lower than fuel-related costs used to determine rates for such period resulting in an over-collection of fuel-related costs. As of September 30, 2015, fuel-related costs outside of the approved range were $5 million and are included in “Commodity cost recovery” in Alliant Energy’s and WPL’s regulatory liabilities table above. WPL’s Retail Fuel-related Rate Filing (2014 Test Year) - Pursuant to a 2013 PSCW order, WPL’s 2014 fuel-related costs were subject to deferral since they were outside an annual bandwidth of plus or minus 2% of the approved annual forecasted fuel-related costs. Retail fuel-related costs incurred by WPL through December 31, 2014 were higher than fuel-related costs used to determine rates for such period resulting in an under-collection of fuel-related costs for 2014 of $33 million (including $28 million outside the approved range for 2014). The $28 million of deferred fuel-related costs is included in “Commodity cost recovery” in Alliant Energy’s and WPL’s regulatory assets table above. In July 2015, WPL received an order from the PSCW authorizing an annual retail electric rate increase of $28 million, or approximately 3%, effective January 1, 2016 to recover the 2014 Test Year deferred fuel-related costs.

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