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Regulatory Matters | 9 Months Ended
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Sep. 30, 2014
Regulatory Matters [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, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013
Tax-related |  | $937.6 |  |  |  | $829.7 |  |  |  | $910.6 |  |  |  | $798.6 |  |  |  | $27.0 |  |  |  | $31.1 |
Pension and OPEB costs | 345.4 |  |  | 355.3 |  |  | 170.2 |  |  | 174.2 |  |  | 175.2 |  |  | 181.1 |
AROs | 74.6 |  |  | 65.7 |  |  | 43.1 |  |  | 36.7 |  |  | 31.5 |  |  | 29.0 |
Emission allowances | 28.0 |  |  | 30.0 |  |  | 28.0 |  |  | 30.0 |  |  | — |  |  | — |
Environmental-related costs | 26.6 |  |  | 25.0 |  |  | 22.0 |  |  | 21.0 |  |  | 4.6 |  |  | 4.0 |
Derivatives | 23.3 |  |  | 21.1 |  |  | 17.7 |  |  | 5.9 |  |  | 5.6 |  |  | 15.2 |
Other | 88.8 |  |  | 86.4 |  |  | 35.2 |  |  | 47.1 |  |  | 53.6 |  |  | 39.3 |
|  | $1,524.3 |  |  |  | $1,413.2 |  |  |  | $1,226.8 |  |  |  | $1,113.5 |  |  |  | $297.5 |  |  |  | $299.7 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013
Cost of removal obligations |  | $422.7 |  |  |  | $418.9 |  |  |  | $280.9 |  |  |  | $277.7 |  |  |  | $141.8 |  |  |  | $141.2 |
IPL’s tax benefit riders | 266.3 |  |  | 265.4 |  |  | 266.3 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 67.5 |  |  | 52.7 |  |  | 8.6 |  |  | 9.3 |  |  | 58.9 |  |  | 43.4 |
Derivatives | 41.2 |  |  | 7.2 |  |  | 8.4 |  |  | 3.6 |  |  | 32.8 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 14.1 |  |  | 14.6 |  |  | 14.1 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 13.7 |  |  | 21.6 |  |  | 13.7 |  |  | 21.6 |  |  | — |  |  | — |
Other | 51.3 |  |  | 41.1 |  |  | 31.2 |  |  | 22.7 |  |  | 20.1 |  |  | 18.4 |
|  | $876.8 |  |  |  | $821.5 |  |  |  | $623.2 |  |  |  | $614.9 |  |  |  | $253.6 |  |  |  | $206.6 |
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, 2014, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due to property-related differences for qualifying repair expenditures and tax accounting method changes in 2014 for cost of removal expenditures and generation repair expenditures at IPL. The increase related to the tax accounting method changes was offset by increased regulatory liabilities as discussed below in “IPL’s tax benefit riders.” Derivatives - Refer to Note 13 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 and allocation of insurance proceeds from floods in 2008. For the nine months ended September 30, 2014, Alliant Energy and IPL utilized “IPL’s tax benefit riders” regulatory liabilities to credit IPL’s Iowa retail electric and gas customers’ bills as follows (in millions):
Electric tax benefit rider |  | $64 |
Gas tax benefit rider | 9 |
|  | $73 |
In 2013, the U.S. Department of the Treasury issued tangible property regulations clarifying the tax treatment of costs incurred to acquire, maintain or improve tangible property and to retire and remove depreciable property. The regulations clarified the ability to deduct cost of removal expenditures on partial dispositions of assets. In 2014, the IRS issued implementation guidance related to these tangible property regulations, which allowed companies to file a tax accounting method change to deduct cost of removal expenditures on partial dispositions that were previously capitalized. During the second quarter of 2014, Alliant Energy, IPL and WPL implemented this tax accounting method change, which will result in the inclusion of additional tax deductions on Alliant Energy’s U.S. federal income tax return for the calendar year 2014. In 2013, the IRS also issued guidance that clarified acceptable units of property to be used when assessing whether costs incurred for electric generation projects may be deducted as repair expenditures or if they must be capitalized. After assessing the guidance, Alliant Energy, IPL and WPL decided in the third quarter of 2014 to implement the new units of property by filing a tax accounting method change as part of Alliant Energy’s U.S. federal income tax return for the calendar year 2013. IPL currently anticipates crediting its related tax benefits from these two tax accounting method changes to its Iowa retail electric and gas customers in the future, and as a result, Alliant Energy and IPL recorded an increase of $74 million to IPL’s tax benefit riders regulatory liabilities and IPL’s tax-related regulatory assets during the nine months ended September 30, 2014. Refer to Note 9 for additional details regarding the tax benefit riders. Utility Rate Cases - WPL’s Wisconsin Retail Electric and Gas Rate Case (2015/2016 Test Period) - In July 2014, WPL received an order from the PSCW authorizing WPL to implement its retail base rate filing as requested. The order is based on a forward-looking test period that includes 2015 and 2016 and authorizes WPL to maintain customer base rates for its retail electric customers at their current levels through the end of 2016. The retail electric base rate case included a return of and a return on costs for emission controls projects at Columbia Units 1 and 2 and Edgewater Unit 5, generation performance and reliability improvements at Columbia Units 1 and 2, other ongoing capital expenditures, and an increase in electric transmission service expense. The additional revenue requirement for these cost increases was offset by the impact of changes in the amortization of regulatory liabilities associated with energy efficiency cost recoveries and increased sales volumes. The order also authorizes WPL to implement a $5 million decrease in annual base rates for its retail gas customers effective January 1, 2015 followed by a freeze of such gas base rates through the end of 2016. IPL’s Iowa Retail Electric Rate Case (2013 Test Year) - In September 2014, the IUB approved IPL’s settlement agreement as requested. The settlement agreement extends IPL’s Iowa retail electric base rate freeze through 2016 and provides retail electric customer billing credits of $105 million in aggregate, including targeting $70 million in 2014 (beginning May 2014), $25 million in 2015 and $10 million in 2016. For the three and nine months ended September 30, 2014, IPL recorded $26 million and $46 million, respectively, of such billing credits to reduce retail electric customers’ bills. IPL’s Iowa Retail Electric Rate Case (2009 Test Year) - Electric Tax Benefit Rider - In 2013, the IUB authorized IPL to reduce the electric tax benefit rider billing credits on customers’ bills by $24 million in 2013 and $15 million in 2014 to recognize the revenue requirement impact of the changes in tax accounting methods. For the three and nine months ended September 30, the revenue requirement adjustment recognized by both Alliant Energy and IPL is included in the table below (in millions). The revenue requirement adjustment resulted in increases to electric revenues in their income statements and was recognized through the energy adjustment clause as a reduction of the credits on IPL’s Iowa retail electric customers’ bills from the electric tax benefit rider.
| Three Months |  | Nine Months
| 2014 |  | 2013 |  | 2014 |  | 2013
Revenue requirement adjustment |  | $4 |  |  |  | $7 |  |  |  | $11 |  |  |  | $18 |
WPL’s Retail Fuel-related Rate Filing (2015 Test Year) - In June 2014, WPL filed a request with the PSCW to increase annual rates for WPL’s retail electric customers by $55 million, or approximately 5%, in 2015. The increase includes $41 million of anticipated increases in the retail share of electric fuel-related costs in 2015 attributable to $28 million for higher retail electric fuel-related costs per MWh anticipated in 2015 and $13 million from the impact of increased sales volumes approved in the retail electric base rate case for 2015. In addition, WPL’s request includes $14 million to recover a portion of the under-collection of fuel-related costs projected for 2014. Any rate changes granted from this request are expected to be effective on January 1, 2015. WPL currently expects a decision from the PSCW regarding this rate filing by the end of 2014. WPL’s Retail Fuel-related Rate Filing (2014 Test Year) - In December 2013, WPL received an order from the PSCW authorizing an annual retail electric rate increase of $19 million, or approximately 2%, effective January 1, 2014 to reflect anticipated increases in retail fuel-related costs in 2014 compared to the fuel-related cost estimates used to determine rates for 2013. WPL’s 2014 fuel-related costs will be subject to deferral if they fall 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, 2014 were higher than fuel-related costs used to determine rates for such period resulting in an under-collection of fuel-related costs during the nine months ended September 30, 2014. As of September 30, 2014, Alliant Energy and WPL recorded $21 million in “Regulatory assets” on their balance sheets for fuel-related costs incurred during the nine months ended September 30, 2014 that are expected to fall outside the approved bandwidth of plus or minus 2% for 2014. The $21 million of deferred fuel-related costs is included in “Other” in Alliant Energy’s and WPL’s regulatory assets tables above.
IPL [Member] |
Regulatory Matters [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, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013
Tax-related |  | $937.6 |  |  |  | $829.7 |  |  |  | $910.6 |  |  |  | $798.6 |  |  |  | $27.0 |  |  |  | $31.1 |
Pension and OPEB costs | 345.4 |  |  | 355.3 |  |  | 170.2 |  |  | 174.2 |  |  | 175.2 |  |  | 181.1 |
AROs | 74.6 |  |  | 65.7 |  |  | 43.1 |  |  | 36.7 |  |  | 31.5 |  |  | 29.0 |
Emission allowances | 28.0 |  |  | 30.0 |  |  | 28.0 |  |  | 30.0 |  |  | — |  |  | — |
Environmental-related costs | 26.6 |  |  | 25.0 |  |  | 22.0 |  |  | 21.0 |  |  | 4.6 |  |  | 4.0 |
Derivatives | 23.3 |  |  | 21.1 |  |  | 17.7 |  |  | 5.9 |  |  | 5.6 |  |  | 15.2 |
Other | 88.8 |  |  | 86.4 |  |  | 35.2 |  |  | 47.1 |  |  | 53.6 |  |  | 39.3 |
|  | $1,524.3 |  |  |  | $1,413.2 |  |  |  | $1,226.8 |  |  |  | $1,113.5 |  |  |  | $297.5 |  |  |  | $299.7 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013
Cost of removal obligations |  | $422.7 |  |  |  | $418.9 |  |  |  | $280.9 |  |  |  | $277.7 |  |  |  | $141.8 |  |  |  | $141.2 |
IPL’s tax benefit riders | 266.3 |  |  | 265.4 |  |  | 266.3 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 67.5 |  |  | 52.7 |  |  | 8.6 |  |  | 9.3 |  |  | 58.9 |  |  | 43.4 |
Derivatives | 41.2 |  |  | 7.2 |  |  | 8.4 |  |  | 3.6 |  |  | 32.8 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 14.1 |  |  | 14.6 |  |  | 14.1 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 13.7 |  |  | 21.6 |  |  | 13.7 |  |  | 21.6 |  |  | — |  |  | — |
Other | 51.3 |  |  | 41.1 |  |  | 31.2 |  |  | 22.7 |  |  | 20.1 |  |  | 18.4 |
|  | $876.8 |  |  |  | $821.5 |  |  |  | $623.2 |  |  |  | $614.9 |  |  |  | $253.6 |  |  |  | $206.6 |
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, 2014, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due to property-related differences for qualifying repair expenditures and tax accounting method changes in 2014 for cost of removal expenditures and generation repair expenditures at IPL. The increase related to the tax accounting method changes was offset by increased regulatory liabilities as discussed below in “IPL’s tax benefit riders.” Derivatives - Refer to Note 13 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 and allocation of insurance proceeds from floods in 2008. For the nine months ended September 30, 2014, Alliant Energy and IPL utilized “IPL’s tax benefit riders” regulatory liabilities to credit IPL’s Iowa retail electric and gas customers’ bills as follows (in millions):
Electric tax benefit rider |  | $64 |
Gas tax benefit rider | 9 |
|  | $73 |
In 2013, the U.S. Department of the Treasury issued tangible property regulations clarifying the tax treatment of costs incurred to acquire, maintain or improve tangible property and to retire and remove depreciable property. The regulations clarified the ability to deduct cost of removal expenditures on partial dispositions of assets. In 2014, the IRS issued implementation guidance related to these tangible property regulations, which allowed companies to file a tax accounting method change to deduct cost of removal expenditures on partial dispositions that were previously capitalized. During the second quarter of 2014, Alliant Energy, IPL and WPL implemented this tax accounting method change, which will result in the inclusion of additional tax deductions on Alliant Energy’s U.S. federal income tax return for the calendar year 2014. In 2013, the IRS also issued guidance that clarified acceptable units of property to be used when assessing whether costs incurred for electric generation projects may be deducted as repair expenditures or if they must be capitalized. After assessing the guidance, Alliant Energy, IPL and WPL decided in the third quarter of 2014 to implement the new units of property by filing a tax accounting method change as part of Alliant Energy’s U.S. federal income tax return for the calendar year 2013. IPL currently anticipates crediting its related tax benefits from these two tax accounting method changes to its Iowa retail electric and gas customers in the future, and as a result, Alliant Energy and IPL recorded an increase of $74 million to IPL’s tax benefit riders regulatory liabilities and IPL’s tax-related regulatory assets during the nine months ended September 30, 2014. Refer to Note 9 for additional details regarding the tax benefit riders. Utility Rate Cases - WPL’s Wisconsin Retail Electric and Gas Rate Case (2015/2016 Test Period) - In July 2014, WPL received an order from the PSCW authorizing WPL to implement its retail base rate filing as requested. The order is based on a forward-looking test period that includes 2015 and 2016 and authorizes WPL to maintain customer base rates for its retail electric customers at their current levels through the end of 2016. The retail electric base rate case included a return of and a return on costs for emission controls projects at Columbia Units 1 and 2 and Edgewater Unit 5, generation performance and reliability improvements at Columbia Units 1 and 2, other ongoing capital expenditures, and an increase in electric transmission service expense. The additional revenue requirement for these cost increases was offset by the impact of changes in the amortization of regulatory liabilities associated with energy efficiency cost recoveries and increased sales volumes. The order also authorizes WPL to implement a $5 million decrease in annual base rates for its retail gas customers effective January 1, 2015 followed by a freeze of such gas base rates through the end of 2016. IPL’s Iowa Retail Electric Rate Case (2013 Test Year) - In September 2014, the IUB approved IPL’s settlement agreement as requested. The settlement agreement extends IPL’s Iowa retail electric base rate freeze through 2016 and provides retail electric customer billing credits of $105 million in aggregate, including targeting $70 million in 2014 (beginning May 2014), $25 million in 2015 and $10 million in 2016. For the three and nine months ended September 30, 2014, IPL recorded $26 million and $46 million, respectively, of such billing credits to reduce retail electric customers’ bills. IPL’s Iowa Retail Electric Rate Case (2009 Test Year) - Electric Tax Benefit Rider - In 2013, the IUB authorized IPL to reduce the electric tax benefit rider billing credits on customers’ bills by $24 million in 2013 and $15 million in 2014 to recognize the revenue requirement impact of the changes in tax accounting methods. For the three and nine months ended September 30, the revenue requirement adjustment recognized by both Alliant Energy and IPL is included in the table below (in millions). The revenue requirement adjustment resulted in increases to electric revenues in their income statements and was recognized through the energy adjustment clause as a reduction of the credits on IPL’s Iowa retail electric customers’ bills from the electric tax benefit rider.
| Three Months |  | Nine Months
| 2014 |  | 2013 |  | 2014 |  | 2013
Revenue requirement adjustment |  | $4 |  |  |  | $7 |  |  |  | $11 |  |  |  | $18 |
WPL’s Retail Fuel-related Rate Filing (2015 Test Year) - In June 2014, WPL filed a request with the PSCW to increase annual rates for WPL’s retail electric customers by $55 million, or approximately 5%, in 2015. The increase includes $41 million of anticipated increases in the retail share of electric fuel-related costs in 2015 attributable to $28 million for higher retail electric fuel-related costs per MWh anticipated in 2015 and $13 million from the impact of increased sales volumes approved in the retail electric base rate case for 2015. In addition, WPL’s request includes $14 million to recover a portion of the under-collection of fuel-related costs projected for 2014. Any rate changes granted from this request are expected to be effective on January 1, 2015. WPL currently expects a decision from the PSCW regarding this rate filing by the end of 2014. WPL’s Retail Fuel-related Rate Filing (2014 Test Year) - In December 2013, WPL received an order from the PSCW authorizing an annual retail electric rate increase of $19 million, or approximately 2%, effective January 1, 2014 to reflect anticipated increases in retail fuel-related costs in 2014 compared to the fuel-related cost estimates used to determine rates for 2013. WPL’s 2014 fuel-related costs will be subject to deferral if they fall 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, 2014 were higher than fuel-related costs used to determine rates for such period resulting in an under-collection of fuel-related costs during the nine months ended September 30, 2014. As of September 30, 2014, Alliant Energy and WPL recorded $21 million in “Regulatory assets” on their balance sheets for fuel-related costs incurred during the nine months ended September 30, 2014 that are expected to fall outside the approved bandwidth of plus or minus 2% for 2014. The $21 million of deferred fuel-related costs is included in “Other” in Alliant Energy’s and WPL’s regulatory assets tables above.
WPL [Member] |
Regulatory Matters [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, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013
Tax-related |  | $937.6 |  |  |  | $829.7 |  |  |  | $910.6 |  |  |  | $798.6 |  |  |  | $27.0 |  |  |  | $31.1 |
Pension and OPEB costs | 345.4 |  |  | 355.3 |  |  | 170.2 |  |  | 174.2 |  |  | 175.2 |  |  | 181.1 |
AROs | 74.6 |  |  | 65.7 |  |  | 43.1 |  |  | 36.7 |  |  | 31.5 |  |  | 29.0 |
Emission allowances | 28.0 |  |  | 30.0 |  |  | 28.0 |  |  | 30.0 |  |  | — |  |  | — |
Environmental-related costs | 26.6 |  |  | 25.0 |  |  | 22.0 |  |  | 21.0 |  |  | 4.6 |  |  | 4.0 |
Derivatives | 23.3 |  |  | 21.1 |  |  | 17.7 |  |  | 5.9 |  |  | 5.6 |  |  | 15.2 |
Other | 88.8 |  |  | 86.4 |  |  | 35.2 |  |  | 47.1 |  |  | 53.6 |  |  | 39.3 |
|  | $1,524.3 |  |  |  | $1,413.2 |  |  |  | $1,226.8 |  |  |  | $1,113.5 |  |  |  | $297.5 |  |  |  | $299.7 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013 |  | September 30, 2014 |  | December 31, 2013
Cost of removal obligations |  | $422.7 |  |  |  | $418.9 |  |  |  | $280.9 |  |  |  | $277.7 |  |  |  | $141.8 |  |  |  | $141.2 |
IPL’s tax benefit riders | 266.3 |  |  | 265.4 |  |  | 266.3 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 67.5 |  |  | 52.7 |  |  | 8.6 |  |  | 9.3 |  |  | 58.9 |  |  | 43.4 |
Derivatives | 41.2 |  |  | 7.2 |  |  | 8.4 |  |  | 3.6 |  |  | 32.8 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 14.1 |  |  | 14.6 |  |  | 14.1 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 13.7 |  |  | 21.6 |  |  | 13.7 |  |  | 21.6 |  |  | — |  |  | — |
Other | 51.3 |  |  | 41.1 |  |  | 31.2 |  |  | 22.7 |  |  | 20.1 |  |  | 18.4 |
|  | $876.8 |  |  |  | $821.5 |  |  |  | $623.2 |  |  |  | $614.9 |  |  |  | $253.6 |  |  |  | $206.6 |
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, 2014, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due to property-related differences for qualifying repair expenditures and tax accounting method changes in 2014 for cost of removal expenditures and generation repair expenditures at IPL. The increase related to the tax accounting method changes was offset by increased regulatory liabilities as discussed below in “IPL’s tax benefit riders.” Derivatives - Refer to Note 13 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 and allocation of insurance proceeds from floods in 2008. For the nine months ended September 30, 2014, Alliant Energy and IPL utilized “IPL’s tax benefit riders” regulatory liabilities to credit IPL’s Iowa retail electric and gas customers’ bills as follows (in millions):
Electric tax benefit rider |  | $64 |
Gas tax benefit rider | 9 |
|  | $73 |
In 2013, the U.S. Department of the Treasury issued tangible property regulations clarifying the tax treatment of costs incurred to acquire, maintain or improve tangible property and to retire and remove depreciable property. The regulations clarified the ability to deduct cost of removal expenditures on partial dispositions of assets. In 2014, the IRS issued implementation guidance related to these tangible property regulations, which allowed companies to file a tax accounting method change to deduct cost of removal expenditures on partial dispositions that were previously capitalized. During the second quarter of 2014, Alliant Energy, IPL and WPL implemented this tax accounting method change, which will result in the inclusion of additional tax deductions on Alliant Energy’s U.S. federal income tax return for the calendar year 2014. In 2013, the IRS also issued guidance that clarified acceptable units of property to be used when assessing whether costs incurred for electric generation projects may be deducted as repair expenditures or if they must be capitalized. After assessing the guidance, Alliant Energy, IPL and WPL decided in the third quarter of 2014 to implement the new units of property by filing a tax accounting method change as part of Alliant Energy’s U.S. federal income tax return for the calendar year 2013. IPL currently anticipates crediting its related tax benefits from these two tax accounting method changes to its Iowa retail electric and gas customers in the future, and as a result, Alliant Energy and IPL recorded an increase of $74 million to IPL’s tax benefit riders regulatory liabilities and IPL’s tax-related regulatory assets during the nine months ended September 30, 2014. Refer to Note 9 for additional details regarding the tax benefit riders. Utility Rate Cases - WPL’s Wisconsin Retail Electric and Gas Rate Case (2015/2016 Test Period) - In July 2014, WPL received an order from the PSCW authorizing WPL to implement its retail base rate filing as requested. The order is based on a forward-looking test period that includes 2015 and 2016 and authorizes WPL to maintain customer base rates for its retail electric customers at their current levels through the end of 2016. The retail electric base rate case included a return of and a return on costs for emission controls projects at Columbia Units 1 and 2 and Edgewater Unit 5, generation performance and reliability improvements at Columbia Units 1 and 2, other ongoing capital expenditures, and an increase in electric transmission service expense. The additional revenue requirement for these cost increases was offset by the impact of changes in the amortization of regulatory liabilities associated with energy efficiency cost recoveries and increased sales volumes. The order also authorizes WPL to implement a $5 million decrease in annual base rates for its retail gas customers effective January 1, 2015 followed by a freeze of such gas base rates through the end of 2016. IPL’s Iowa Retail Electric Rate Case (2013 Test Year) - In September 2014, the IUB approved IPL’s settlement agreement as requested. The settlement agreement extends IPL’s Iowa retail electric base rate freeze through 2016 and provides retail electric customer billing credits of $105 million in aggregate, including targeting $70 million in 2014 (beginning May 2014), $25 million in 2015 and $10 million in 2016. For the three and nine months ended September 30, 2014, IPL recorded $26 million and $46 million, respectively, of such billing credits to reduce retail electric customers’ bills. IPL’s Iowa Retail Electric Rate Case (2009 Test Year) - Electric Tax Benefit Rider - In 2013, the IUB authorized IPL to reduce the electric tax benefit rider billing credits on customers’ bills by $24 million in 2013 and $15 million in 2014 to recognize the revenue requirement impact of the changes in tax accounting methods. For the three and nine months ended September 30, the revenue requirement adjustment recognized by both Alliant Energy and IPL is included in the table below (in millions). The revenue requirement adjustment resulted in increases to electric revenues in their income statements and was recognized through the energy adjustment clause as a reduction of the credits on IPL’s Iowa retail electric customers’ bills from the electric tax benefit rider.
| Three Months |  | Nine Months
| 2014 |  | 2013 |  | 2014 |  | 2013
Revenue requirement adjustment |  | $4 |  |  |  | $7 |  |  |  | $11 |  |  |  | $18 |
WPL’s Retail Fuel-related Rate Filing (2015 Test Year) - In June 2014, WPL filed a request with the PSCW to increase annual rates for WPL’s retail electric customers by $55 million, or approximately 5%, in 2015. The increase includes $41 million of anticipated increases in the retail share of electric fuel-related costs in 2015 attributable to $28 million for higher retail electric fuel-related costs per MWh anticipated in 2015 and $13 million from the impact of increased sales volumes approved in the retail electric base rate case for 2015. In addition, WPL’s request includes $14 million to recover a portion of the under-collection of fuel-related costs projected for 2014. Any rate changes granted from this request are expected to be effective on January 1, 2015. WPL currently expects a decision from the PSCW regarding this rate filing by the end of 2014. WPL’s Retail Fuel-related Rate Filing (2014 Test Year) - In December 2013, WPL received an order from the PSCW authorizing an annual retail electric rate increase of $19 million, or approximately 2%, effective January 1, 2014 to reflect anticipated increases in retail fuel-related costs in 2014 compared to the fuel-related cost estimates used to determine rates for 2013. WPL’s 2014 fuel-related costs will be subject to deferral if they fall 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, 2014 were higher than fuel-related costs used to determine rates for such period resulting in an under-collection of fuel-related costs during the nine months ended September 30, 2014. As of September 30, 2014, Alliant Energy and WPL recorded $21 million in “Regulatory assets” on their balance sheets for fuel-related costs incurred during the nine months ended September 30, 2014 that are expected to fall outside the approved bandwidth of plus or minus 2% for 2014. The $21 million of deferred fuel-related costs is included in “Other” in Alliant Energy’s and WPL’s regulatory assets tables above.

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