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Regulatory Matters | 3 Months Ended
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Mar. 31, 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
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Tax-related |  | $834.0 |  |  |  | $829.7 |  |  |  | $808.3 |  |  |  | $798.6 |  |  |  | $25.7 |  |  |  | $31.1 |
Pension and OPEB costs | 351.8 |  |  | 355.3 |  |  | 172.6 |  |  | 174.2 |  |  | 179.2 |  |  | 181.1 |
AROs | 68.5 |  |  | 65.7 |  |  | 38.6 |  |  | 36.7 |  |  | 29.9 |  |  | 29.0 |
Environmental-related costs | 27.8 |  |  | 25.0 |  |  | 23.0 |  |  | 21.0 |  |  | 4.8 |  |  | 4.0 |
Emission allowances | 29.2 |  |  | 30.0 |  |  | 29.2 |  |  | 30.0 |  |  | — |  |  | — |
Derivatives | 9.1 |  |  | 21.1 |  |  | 2.5 |  |  | 5.9 |  |  | 6.6 |  |  | 15.2 |
Other | 96.9 |  |  | 86.4 |  |  | 43.8 |  |  | 47.1 |  |  | 53.1 |  |  | 39.3 |
|  | $1,417.3 |  |  |  | $1,413.2 |  |  |  | $1,118.0 |  |  |  | $1,113.5 |  |  |  | $299.3 |  |  |  | $299.7 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Cost of removal obligations |  | $420.0 |  |  |  | $418.9 |  |  |  | $279.3 |  |  |  | $277.7 |  |  |  | $140.7 |  |  |  | $141.2 |
IPL’s tax benefit riders | 239.8 |  |  | 265.4 |  |  | 239.8 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 64.1 |  |  | 52.7 |  |  | 14.9 |  |  | 9.3 |  |  | 49.2 |  |  | 43.4 |
Derivatives | 33.3 |  |  | 7.2 |  |  | 8.8 |  |  | 3.6 |  |  | 24.5 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 21.2 |  |  | 14.6 |  |  | 21.2 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 18.8 |  |  | 21.6 |  |  | 18.8 |  |  | 21.6 |  |  | — |  |  | — |
Other | 39.2 |  |  | 41.1 |  |  | 21.2 |  |  | 22.7 |  |  | 18.0 |  |  | 18.4 |
|  | $836.4 |  |  |  | $821.5 |  |  |  | $604.0 |  |  |  | $614.9 |  |  |  | $232.4 |  |  |  | $206.6 |
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 and allocation of insurance proceeds from floods in 2008. For the three months ended March 31, 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 |  | $23 |
Gas tax benefit rider | 3 |
|  | $26 |
Refer to Note 8 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 April 2014, after discussions with PSCW staff and intervener groups, WPL filed a retail base rate filing with the PSCW based on a forward-looking test period that includes 2015 and 2016. The filing requested approval for WPL to implement a $5 million decrease in annual base rates for WPL’s retail gas customers effective January 1, 2015 followed by a freeze of such gas base rates through the end of 2016. The filing also requested authority to maintain customer base rates for WPL’s retail electric customers at their current levels through the end of 2016. WPL currently expects a decision from the PSCW regarding this rate filing in the second quarter of 2014. IPL’s Iowa Retail Electric Rate Case (2013 Test Year) - In March 2014, after reaching a unanimous agreement with parties to the DAEC PPA proceeding, IPL filed with the IUB a settlement agreement and joint motion for approval of the settlement agreement to extend IPL’s Iowa retail electric base rate freeze through 2016 and provide retail electric customer billing credits of $70 million in 2014 (beginning May 2014), decreasing to $25 million in 2015 and further decreasing to $10 million in 2016. IPL currently expects a decision from the IUB regarding the settlement agreement in the second quarter of 2014. 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 months ended March 31, 2014 and 2013, both Alliant Energy and IPL recognized $3.9 million and $5.5 million, respectively, of the revenue requirement adjustment resulting in increases to electric revenues in their income statements. The revenue requirement adjustment 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. 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 March 31, 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 first quarter of 2014. As of March 31, 2014, Alliant Energy and WPL recorded $10 million in “Regulatory assets” on their balance sheets for fuel-related costs incurred in the first quarter of 2014 that are expected to fall outside the approved bandwidth for 2014. The $10 million of deferred fuel-related costs is included in “Other” in Alliant Energy’s and WPL’s regulatory assets table 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
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Tax-related |  | $834.0 |  |  |  | $829.7 |  |  |  | $808.3 |  |  |  | $798.6 |  |  |  | $25.7 |  |  |  | $31.1 |
Pension and OPEB costs | 351.8 |  |  | 355.3 |  |  | 172.6 |  |  | 174.2 |  |  | 179.2 |  |  | 181.1 |
AROs | 68.5 |  |  | 65.7 |  |  | 38.6 |  |  | 36.7 |  |  | 29.9 |  |  | 29.0 |
Environmental-related costs | 27.8 |  |  | 25.0 |  |  | 23.0 |  |  | 21.0 |  |  | 4.8 |  |  | 4.0 |
Emission allowances | 29.2 |  |  | 30.0 |  |  | 29.2 |  |  | 30.0 |  |  | — |  |  | — |
Derivatives | 9.1 |  |  | 21.1 |  |  | 2.5 |  |  | 5.9 |  |  | 6.6 |  |  | 15.2 |
Other | 96.9 |  |  | 86.4 |  |  | 43.8 |  |  | 47.1 |  |  | 53.1 |  |  | 39.3 |
|  | $1,417.3 |  |  |  | $1,413.2 |  |  |  | $1,118.0 |  |  |  | $1,113.5 |  |  |  | $299.3 |  |  |  | $299.7 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Cost of removal obligations |  | $420.0 |  |  |  | $418.9 |  |  |  | $279.3 |  |  |  | $277.7 |  |  |  | $140.7 |  |  |  | $141.2 |
IPL’s tax benefit riders | 239.8 |  |  | 265.4 |  |  | 239.8 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 64.1 |  |  | 52.7 |  |  | 14.9 |  |  | 9.3 |  |  | 49.2 |  |  | 43.4 |
Derivatives | 33.3 |  |  | 7.2 |  |  | 8.8 |  |  | 3.6 |  |  | 24.5 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 21.2 |  |  | 14.6 |  |  | 21.2 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 18.8 |  |  | 21.6 |  |  | 18.8 |  |  | 21.6 |  |  | — |  |  | — |
Other | 39.2 |  |  | 41.1 |  |  | 21.2 |  |  | 22.7 |  |  | 18.0 |  |  | 18.4 |
|  | $836.4 |  |  |  | $821.5 |  |  |  | $604.0 |  |  |  | $614.9 |  |  |  | $232.4 |  |  |  | $206.6 |
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 and allocation of insurance proceeds from floods in 2008. For the three months ended March 31, 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 |  | $23 |
Gas tax benefit rider | 3 |
|  | $26 |
Refer to Note 8 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 April 2014, after discussions with PSCW staff and intervener groups, WPL filed a retail base rate filing with the PSCW based on a forward-looking test period that includes 2015 and 2016. The filing requested approval for WPL to implement a $5 million decrease in annual base rates for WPL’s retail gas customers effective January 1, 2015 followed by a freeze of such gas base rates through the end of 2016. The filing also requested authority to maintain customer base rates for WPL’s retail electric customers at their current levels through the end of 2016. WPL currently expects a decision from the PSCW regarding this rate filing in the second quarter of 2014. IPL’s Iowa Retail Electric Rate Case (2013 Test Year) - In March 2014, after reaching a unanimous agreement with parties to the DAEC PPA proceeding, IPL filed with the IUB a settlement agreement and joint motion for approval of the settlement agreement to extend IPL’s Iowa retail electric base rate freeze through 2016 and provide retail electric customer billing credits of $70 million in 2014 (beginning May 2014), decreasing to $25 million in 2015 and further decreasing to $10 million in 2016. IPL currently expects a decision from the IUB regarding the settlement agreement in the second quarter of 2014. 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 months ended March 31, 2014 and 2013, both Alliant Energy and IPL recognized $3.9 million and $5.5 million, respectively, of the revenue requirement adjustment resulting in increases to electric revenues in their income statements. The revenue requirement adjustment 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. 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 March 31, 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 first quarter of 2014. As of March 31, 2014, Alliant Energy and WPL recorded $10 million in “Regulatory assets” on their balance sheets for fuel-related costs incurred in the first quarter of 2014 that are expected to fall outside the approved bandwidth for 2014. The $10 million of deferred fuel-related costs is included in “Other” in Alliant Energy’s and WPL’s regulatory assets table 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
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Tax-related |  | $834.0 |  |  |  | $829.7 |  |  |  | $808.3 |  |  |  | $798.6 |  |  |  | $25.7 |  |  |  | $31.1 |
Pension and OPEB costs | 351.8 |  |  | 355.3 |  |  | 172.6 |  |  | 174.2 |  |  | 179.2 |  |  | 181.1 |
AROs | 68.5 |  |  | 65.7 |  |  | 38.6 |  |  | 36.7 |  |  | 29.9 |  |  | 29.0 |
Environmental-related costs | 27.8 |  |  | 25.0 |  |  | 23.0 |  |  | 21.0 |  |  | 4.8 |  |  | 4.0 |
Emission allowances | 29.2 |  |  | 30.0 |  |  | 29.2 |  |  | 30.0 |  |  | — |  |  | — |
Derivatives | 9.1 |  |  | 21.1 |  |  | 2.5 |  |  | 5.9 |  |  | 6.6 |  |  | 15.2 |
Other | 96.9 |  |  | 86.4 |  |  | 43.8 |  |  | 47.1 |  |  | 53.1 |  |  | 39.3 |
|  | $1,417.3 |  |  |  | $1,413.2 |  |  |  | $1,118.0 |  |  |  | $1,113.5 |  |  |  | $299.3 |  |  |  | $299.7 |
Regulatory liabilities were comprised of the following items (in millions):
| Alliant Energy |  | IPL |  | WPL
| March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013 |  | March 31, 2014 |  | December 31, 2013
Cost of removal obligations |  | $420.0 |  |  |  | $418.9 |  |  |  | $279.3 |  |  |  | $277.7 |  |  |  | $140.7 |  |  |  | $141.2 |
IPL’s tax benefit riders | 239.8 |  |  | 265.4 |  |  | 239.8 |  |  | 265.4 |  |  | — |  |  | — |
Energy efficiency cost recovery | 64.1 |  |  | 52.7 |  |  | 14.9 |  |  | 9.3 |  |  | 49.2 |  |  | 43.4 |
Derivatives | 33.3 |  |  | 7.2 |  |  | 8.8 |  |  | 3.6 |  |  | 24.5 |  |  | 3.6 |
IPL’s electric transmission cost recovery | 21.2 |  |  | 14.6 |  |  | 21.2 |  |  | 14.6 |  |  | — |  |  | — |
IPL’s electric transmission assets sale | 18.8 |  |  | 21.6 |  |  | 18.8 |  |  | 21.6 |  |  | — |  |  | — |
Other | 39.2 |  |  | 41.1 |  |  | 21.2 |  |  | 22.7 |  |  | 18.0 |  |  | 18.4 |
|  | $836.4 |  |  |  | $821.5 |  |  |  | $604.0 |  |  |  | $614.9 |  |  |  | $232.4 |  |  |  | $206.6 |
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 and allocation of insurance proceeds from floods in 2008. For the three months ended March 31, 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 |  | $23 |
Gas tax benefit rider | 3 |
|  | $26 |
Refer to Note 8 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 April 2014, after discussions with PSCW staff and intervener groups, WPL filed a retail base rate filing with the PSCW based on a forward-looking test period that includes 2015 and 2016. The filing requested approval for WPL to implement a $5 million decrease in annual base rates for WPL’s retail gas customers effective January 1, 2015 followed by a freeze of such gas base rates through the end of 2016. The filing also requested authority to maintain customer base rates for WPL’s retail electric customers at their current levels through the end of 2016. WPL currently expects a decision from the PSCW regarding this rate filing in the second quarter of 2014. IPL’s Iowa Retail Electric Rate Case (2013 Test Year) - In March 2014, after reaching a unanimous agreement with parties to the DAEC PPA proceeding, IPL filed with the IUB a settlement agreement and joint motion for approval of the settlement agreement to extend IPL’s Iowa retail electric base rate freeze through 2016 and provide retail electric customer billing credits of $70 million in 2014 (beginning May 2014), decreasing to $25 million in 2015 and further decreasing to $10 million in 2016. IPL currently expects a decision from the IUB regarding the settlement agreement in the second quarter of 2014. 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 months ended March 31, 2014 and 2013, both Alliant Energy and IPL recognized $3.9 million and $5.5 million, respectively, of the revenue requirement adjustment resulting in increases to electric revenues in their income statements. The revenue requirement adjustment 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. 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 March 31, 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 first quarter of 2014. As of March 31, 2014, Alliant Energy and WPL recorded $10 million in “Regulatory assets” on their balance sheets for fuel-related costs incurred in the first quarter of 2014 that are expected to fall outside the approved bandwidth for 2014. The $10 million of deferred fuel-related costs is included in “Other” in Alliant Energy’s and WPL’s regulatory assets table above.

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