Regulatory Matters (Tables)

12 Months Ended

Dec. 31, 2014

Regulatory Assets [Line Items]

Schedule of Regulatory Assets

At December 31, regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	2014		2013		2014		2013		2014		2013
Tax-related		$955.3		$829.7		$928.0		$798.6		$27.3		$31.1
Pension and OPEB costs	570.2		355.3		287.9		174.2		282.3		181.1
AROs	73.7		65.7		41.4		36.7		32.3		29.0
Derivatives	46.9		21.1		28.0		5.9		18.9		15.2
Commodity cost recovery	31.1		2.0		0.4		0.7		30.7		1.3
Emission allowances	27.4		30.0		27.4		30.0		—		—
Debt redemption costs	16.1		17.9		10.9		12.2		5.2		5.7
Environmental-related costs	16.0		25.0		11.5		21.0		4.5		4.0
Other	47.0		66.5		22.4		34.2		24.6		32.3
		$1,783.7		$1,413.2		$1,357.9		$1,113.5		$425.8		$299.7

Schedule of Regulatory Liabilities

At December 31, regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	2014		2013		2014		2013		2014		2013
Cost of removal obligations		$421.7		$418.9		$279.1		$277.7		$142.6		$141.2
IPL’s tax benefit riders	243.0		265.4		243.0		265.4		—		—
Energy efficiency cost recovery	64.3		52.7		—		9.3		64.3		43.4
IPL’s electric transmission cost recovery	19.4		14.6		19.4		14.6		—		—
Commodity cost recovery	15.4		7.5		15.1		5.5		0.3		2.0
IPL’s electric transmission assets sale	11.3		21.6		11.3		21.6		—		—
Other	46.1		40.8		15.6		20.8		30.5		20.0
		$821.2		$821.5		$583.5		$614.9		$237.7		$206.6

Tax Benefit Riders

In 2014, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by ($22) million as follows (in millions):

Electric tax benefit rider credits		($85	)
Gas tax benefit rider credits	(12		)
Tax accounting method changes	75
		($22	)

Electric Tax Benefit Rider

Alliant Energy and IPL recognize an offsetting reduction to income tax expense for the after-tax amounts credited to IPL’s retail electric customers’ bills in Iowa, resulting in no impact to Alliant Energy’s and IPL’s net income from the electric tax benefit rider as follows (in millions):

	2014		2013		2012
Credit to IPL’s Iowa retail electric customers’ bills with reduction to electric revenues		$85		$79		$83
Income tax benefit resulting from decreased taxable income caused by credits	35		33		35
Income tax benefit representing tax benefits realized from electric tax benefit rider	50		46		48

Revenue Requirement Adjustment

The revenue requirement adjustment resulted in increases to electric revenues in Alliant Energy’s and IPL’s 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 as follows (in millions):

	2014		2013
Revenue requirement adjustment		$15		$24

Gas Tax Benefit Rider

Alliant Energy and IPL utilized gas tax benefit rider-related regulatory liabilities to credit IPL’s Iowa retail gas customers’ bills as follows (in millions):

	2014		2013
Credit to IPL’s Iowa retail gas customers’ bills with reduction to gas revenues		$12		$11
Income tax benefit resulting from decreased taxable income caused by credits	5		4
Income tax benefit representing tax benefits realized from gas tax benefit rider	7		7

Customer Billing Credits

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 of $105 million in aggregate, beginning May 2014 as follows (in millions):

	2014		2015		2016
Billing credits to reduce retail electric customers’ bills		$70		$25		$10

IPL [Member]

Regulatory Assets [Line Items]

Schedule of Regulatory Assets

At December 31, regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	2014		2013		2014		2013		2014		2013
Tax-related		$955.3		$829.7		$928.0		$798.6		$27.3		$31.1
Pension and OPEB costs	570.2		355.3		287.9		174.2		282.3		181.1
AROs	73.7		65.7		41.4		36.7		32.3		29.0
Derivatives	46.9		21.1		28.0		5.9		18.9		15.2
Commodity cost recovery	31.1		2.0		0.4		0.7		30.7		1.3
Emission allowances	27.4		30.0		27.4		30.0		—		—
Debt redemption costs	16.1		17.9		10.9		12.2		5.2		5.7
Environmental-related costs	16.0		25.0		11.5		21.0		4.5		4.0
Other	47.0		66.5		22.4		34.2		24.6		32.3
		$1,783.7		$1,413.2		$1,357.9		$1,113.5		$425.8		$299.7

Schedule of Regulatory Liabilities

At December 31, regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	2014		2013		2014		2013		2014		2013
Cost of removal obligations		$421.7		$418.9		$279.1		$277.7		$142.6		$141.2
IPL’s tax benefit riders	243.0		265.4		243.0		265.4		—		—
Energy efficiency cost recovery	64.3		52.7		—		9.3		64.3		43.4
IPL’s electric transmission cost recovery	19.4		14.6		19.4		14.6		—		—
Commodity cost recovery	15.4		7.5		15.1		5.5		0.3		2.0
IPL’s electric transmission assets sale	11.3		21.6		11.3		21.6		—		—
Other	46.1		40.8		15.6		20.8		30.5		20.0
		$821.2		$821.5		$583.5		$614.9		$237.7		$206.6

Tax Benefit Riders

In 2014, Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities decreased by ($22) million as follows (in millions):

Electric tax benefit rider credits		($85	)
Gas tax benefit rider credits	(12		)
Tax accounting method changes	75
		($22	)

Electric Tax Benefit Rider

Alliant Energy and IPL recognize an offsetting reduction to income tax expense for the after-tax amounts credited to IPL’s retail electric customers’ bills in Iowa, resulting in no impact to Alliant Energy’s and IPL’s net income from the electric tax benefit rider as follows (in millions):

	2014		2013		2012
Credit to IPL’s Iowa retail electric customers’ bills with reduction to electric revenues		$85		$79		$83
Income tax benefit resulting from decreased taxable income caused by credits	35		33		35
Income tax benefit representing tax benefits realized from electric tax benefit rider	50		46		48

Revenue Requirement Adjustment

The revenue requirement adjustment resulted in increases to electric revenues in Alliant Energy’s and IPL’s 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 as follows (in millions):

	2014		2013
Revenue requirement adjustment		$15		$24

Gas Tax Benefit Rider

Alliant Energy and IPL utilized gas tax benefit rider-related regulatory liabilities to credit IPL’s Iowa retail gas customers’ bills as follows (in millions):

	2014		2013
Credit to IPL’s Iowa retail gas customers’ bills with reduction to gas revenues		$12		$11
Income tax benefit resulting from decreased taxable income caused by credits	5		4
Income tax benefit representing tax benefits realized from gas tax benefit rider	7		7

Customer Billing Credits

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 of $105 million in aggregate, beginning May 2014 as follows (in millions):

	2014		2015		2016
Billing credits to reduce retail electric customers’ bills		$70		$25		$10

WPL [Member]

Regulatory Assets [Line Items]

Schedule of Regulatory Assets

At December 31, regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	2014		2013		2014		2013		2014		2013
Tax-related		$955.3		$829.7		$928.0		$798.6		$27.3		$31.1
Pension and OPEB costs	570.2		355.3		287.9		174.2		282.3		181.1
AROs	73.7		65.7		41.4		36.7		32.3		29.0
Derivatives	46.9		21.1		28.0		5.9		18.9		15.2
Commodity cost recovery	31.1		2.0		0.4		0.7		30.7		1.3
Emission allowances	27.4		30.0		27.4		30.0		—		—
Debt redemption costs	16.1		17.9		10.9		12.2		5.2		5.7
Environmental-related costs	16.0		25.0		11.5		21.0		4.5		4.0
Other	47.0		66.5		22.4		34.2		24.6		32.3
		$1,783.7		$1,413.2		$1,357.9		$1,113.5		$425.8		$299.7

Schedule of Regulatory Liabilities

At December 31, regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	2014		2013		2014		2013		2014		2013
Cost of removal obligations		$421.7		$418.9		$279.1		$277.7		$142.6		$141.2
IPL’s tax benefit riders	243.0		265.4		243.0		265.4		—		—
Energy efficiency cost recovery	64.3		52.7		—		9.3		64.3		43.4
IPL’s electric transmission cost recovery	19.4		14.6		19.4		14.6		—		—
Commodity cost recovery	15.4		7.5		15.1		5.5		0.3		2.0
IPL’s electric transmission assets sale	11.3		21.6		11.3		21.6		—		—
Other	46.1		40.8		15.6		20.8		30.5		20.0
		$821.2		$821.5		$583.5		$614.9		$237.7		$206.6