Regulatory Matters (Tables)

9 Months Ended

Sep. 30, 2014

Regulatory Assets [Line Items]

Regulatory Assets

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

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 Benefit Riders

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

Revenue Requirement Adjustment

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

IPL [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

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 Benefit Riders

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

Revenue Requirement Adjustment

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 [Member]

Regulatory Assets [Line Items]

Regulatory Assets

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

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