Summary Of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2013

Schedule of Average Rates of Depreciation

The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:

	IPL			WPL
	2013	2012	2011	2013 (a)	2012	2011
Electric - generation	3.6%	3.7%	3.5%	3.3%	3.2%	3.3%
Electric - distribution	2.5%	2.5%	2.4%	2.7%	2.9%	2.9%
Gas	3.4%	3.4%	3.5%	2.5%	2.6%	2.6%
Other	4.4%	4.5%	4.8%	5.1%	5.3%	5.2%

(a) In 2012, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2013 as a result of a recently completed depreciation study. In 2013, the PSCW and FERC issued orders approving WPL’s requests to revise depreciation rates associated with the acquisition of Riverside effective January 1, 2013.

Schedule of Allowance for Funds Used During Construction Recovery Rate

The AFUDC recovery rates, computed in accordance with the prescribed regulatory formula, were as follows:

	2013	2012	2011
IPL (FERC formula)	8.2%	8.2%	8.5%
WPL (PSCW formula - retail jurisdiction) (a)	8.2%	8.8%	8.8%
WPL (FERC formula - wholesale jurisdiction)	4.5%	7.9%	6.2%

(a) Consistent with the PSCW’s retail rate case order issued in 2009, WPL accrued AFUDC on 100% of CWIP related to the Edgewater Unit 5 SCR emission controls project and the Columbia Units 1 and 2 scrubber and baghouse emission controls project in 2012 and 2011. Consistent with the PSCW’s retail rate case order issued in 2012, WPL earned a return on 50% of the estimated CWIP related to its Columbia Units 1 and 2 scrubber and baghouse emission controls project for 2013 and accrued AFUDC on the remaining 50% in 2013.

Schedule of Emission Allowance Amortization Expenses

Amortization of emission allowances is based upon a weighted average cost for each category of vintage year utilized during the reporting period and is recorded in “Electric production fuel and energy purchases” in the Consolidated Statements of Income as follows (in millions):

	Alliant Energy			IPL			WPL
	2013	2012	2011	2013	2012	2011	2013	2012	2011
Amortization expense	$—	$—	$13.4	$—	$—	$12.9	$—	$—	$0.5

Schedule of Allowance for Doubtful Accounts

Allowance for doubtful accounts at December 31 was as follows (in millions):

	Alliant Energy				IPL				WPL
	2013		2012		2013		2012		2013		2012
Customer (a)		$1.4		$1.3		$—		$—		$1.4		$1.3
Other	3.4		2.7		0.7		0.7		0.3		0.5
		$4.8		$4.0		$0.7		$0.7		$1.7		$1.8

(a) Refer to Note 5(a) for discussion of IPL’s allowance for doubtful accounts, which is included in its sales of accounts receivable program.

IPL [Member]

Schedule of Average Rates of Depreciation

The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:

	IPL			WPL
	2013	2012	2011	2013 (a)	2012	2011
Electric - generation	3.6%	3.7%	3.5%	3.3%	3.2%	3.3%
Electric - distribution	2.5%	2.5%	2.4%	2.7%	2.9%	2.9%
Gas	3.4%	3.4%	3.5%	2.5%	2.6%	2.6%
Other	4.4%	4.5%	4.8%	5.1%	5.3%	5.2%

(a) In 2012, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2013 as a result of a recently completed depreciation study. In 2013, the PSCW and FERC issued orders approving WPL’s requests to revise depreciation rates associated with the acquisition of Riverside effective January 1, 2013.

Schedule of Allowance for Funds Used During Construction Recovery Rate

The AFUDC recovery rates, computed in accordance with the prescribed regulatory formula, were as follows:

	2013	2012	2011
IPL (FERC formula)	8.2%	8.2%	8.5%
WPL (PSCW formula - retail jurisdiction) (a)	8.2%	8.8%	8.8%
WPL (FERC formula - wholesale jurisdiction)	4.5%	7.9%	6.2%

(a) Consistent with the PSCW’s retail rate case order issued in 2009, WPL accrued AFUDC on 100% of CWIP related to the Edgewater Unit 5 SCR emission controls project and the Columbia Units 1 and 2 scrubber and baghouse emission controls project in 2012 and 2011. Consistent with the PSCW’s retail rate case order issued in 2012, WPL earned a return on 50% of the estimated CWIP related to its Columbia Units 1 and 2 scrubber and baghouse emission controls project for 2013 and accrued AFUDC on the remaining 50% in 2013.

Schedule of Emission Allowance Amortization Expenses

Amortization of emission allowances is based upon a weighted average cost for each category of vintage year utilized during the reporting period and is recorded in “Electric production fuel and energy purchases” in the Consolidated Statements of Income as follows (in millions):

	Alliant Energy			IPL			WPL
	2013	2012	2011	2013	2012	2011	2013	2012	2011
Amortization expense	$—	$—	$13.4	$—	$—	$12.9	$—	$—	$0.5

Schedule of Allowance for Doubtful Accounts

Allowance for doubtful accounts at December 31 was as follows (in millions):

	Alliant Energy				IPL				WPL
	2013		2012		2013		2012		2013		2012
Customer (a)		$1.4		$1.3		$—		$—		$1.4		$1.3
Other	3.4		2.7		0.7		0.7		0.3		0.5
		$4.8		$4.0		$0.7		$0.7		$1.7		$1.8

(a) Refer to Note 5(a) for discussion of IPL’s allowance for doubtful accounts, which is included in its sales of accounts receivable program.

WPL [Member]

Schedule of Average Rates of Depreciation

The average rates of depreciation for electric, gas and other properties, consistent with current rate-making practices, were as follows:

	IPL			WPL
	2013	2012	2011	2013 (a)	2012	2011
Electric - generation	3.6%	3.7%	3.5%	3.3%	3.2%	3.3%
Electric - distribution	2.5%	2.5%	2.4%	2.7%	2.9%	2.9%
Gas	3.4%	3.4%	3.5%	2.5%	2.6%	2.6%
Other	4.4%	4.5%	4.8%	5.1%	5.3%	5.2%

(a) In 2012, the PSCW issued an order approving the implementation of updated depreciation rates for WPL effective January 1, 2013 as a result of a recently completed depreciation study. In 2013, the PSCW and FERC issued orders approving WPL’s requests to revise depreciation rates associated with the acquisition of Riverside effective January 1, 2013.

Schedule of Allowance for Funds Used During Construction Recovery Rate

The AFUDC recovery rates, computed in accordance with the prescribed regulatory formula, were as follows:

	2013	2012	2011
IPL (FERC formula)	8.2%	8.2%	8.5%
WPL (PSCW formula - retail jurisdiction) (a)	8.2%	8.8%	8.8%
WPL (FERC formula - wholesale jurisdiction)	4.5%	7.9%	6.2%

(a) Consistent with the PSCW’s retail rate case order issued in 2009, WPL accrued AFUDC on 100% of CWIP related to the Edgewater Unit 5 SCR emission controls project and the Columbia Units 1 and 2 scrubber and baghouse emission controls project in 2012 and 2011. Consistent with the PSCW’s retail rate case order issued in 2012, WPL earned a return on 50% of the estimated CWIP related to its Columbia Units 1 and 2 scrubber and baghouse emission controls project for 2013 and accrued AFUDC on the remaining 50% in 2013.

Schedule of Emission Allowance Amortization Expenses

Amortization of emission allowances is based upon a weighted average cost for each category of vintage year utilized during the reporting period and is recorded in “Electric production fuel and energy purchases” in the Consolidated Statements of Income as follows (in millions):

	Alliant Energy			IPL			WPL
	2013	2012	2011	2013	2012	2011	2013	2012	2011
Amortization expense	$—	$—	$13.4	$—	$—	$12.9	$—	$—	$0.5

Schedule of Allowance for Doubtful Accounts

Allowance for doubtful accounts at December 31 was as follows (in millions):

	Alliant Energy				IPL				WPL
	2013		2012		2013		2012		2013		2012
Customer (a)		$1.4		$1.3		$—		$—		$1.4		$1.3
Other	3.4		2.7		0.7		0.7		0.3		0.5
		$4.8		$4.0		$0.7		$0.7		$1.7		$1.8

(a) Refer to Note 5(a) for discussion of IPL’s allowance for doubtful accounts, which is included in its sales of accounts receivable program.