Summary Of Significant Accounting Policies (Policy)

9 Months Ended

Sep. 30, 2011

Summary Of Significant Accounting Policies

General

(a) General—The interim condensed consolidated financial statements included herein have been prepared by Alliant Energy, IPL and WPL, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with accounting principles generally accepted in the U.S. (GAAP) have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. Alliant Energy's condensed consolidated financial statements include the accounts of Alliant Energy and its consolidated subsidiaries (including IPL, WPL, Resources and Alliant Energy Corporate Services, Inc. (Corporate Services)). IPL's condensed consolidated financial statements include the accounts of IPL and its consolidated subsidiary. WPL's condensed consolidated financial statements include the accounts of WPL and its consolidated subsidiary. These financial statements should be read in conjunction with the financial statements and the notes thereto included in Alliant Energy's, IPL's and WPL's latest combined Annual Report on Form 10-K.

In the opinion of management, all adjustments, which unless otherwise noted are normal and recurring in nature, necessary for a fair presentation of the condensed consolidated results of operations for the three and nine months ended Sep. 30, 2011 and 2010, the condensed consolidated financial position at Sep. 30, 2011 and Dec. 31, 2010, and the condensed consolidated statements of cash flows for the nine months ended Sep. 30, 2011 and 2010 have been made. Results for the nine months ended Sep. 30, 2011 are not necessarily indicative of results that may be expected for the year ending Dec. 31, 2011. A change in management's estimates or assumptions could have a material impact on Alliant Energy's, IPL's and WPL's respective financial condition and results of operations during the period in which such change occurred. Certain prior period amounts have been reclassified on a basis consistent with the current period financial statement presentation.

Regulatory Assets And Regulatory Liabilities

(b) Regulatory Assets and Regulatory Liabilities—

Regulatory assets were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	Sep. 30,		Dec. 31,		Sep. 30,		Dec. 31,		Sep. 30,		Dec. 31,
	2011		2010		2011		2010		2011		2010
Tax-related	$	608.8	$	395.9	$	589.1	$	377.2	$	19.7	$	18.7
Pension and other postretirement benefits costs		350.8		418.9		174.7		217.4		176.1		201.5
Asset retirement obligations		65.2		49.6		48.6		33.2		16.6		16.4
Derivatives		52.1		66.8		20.6		24.0		31.5		42.8
Environmental-related costs		39.4		38.4		32.6		32.1		6.8		6.3
Emission allowances		30.0		—		30.0		—		—		—
IPL's electric transmission service costs		27.0		33.3		27.0		33.3		—		—
Proposed base-load projects costs		23.3		27.3		16.6		18.9		6.7		8.4
Debt redemption costs		22.2		23.7		15.4		16.5		6.8		7.2
Other		76.9		87.8		48.2		47.0		28.7		40.8
	$	1,295.7	$	1,141.7	$	1,002.8	$	799.6	$	292.9	$	342.1

Regulatory liabilities were comprised of the following items (in millions):

	Alliant Energy				IPL				WPL
	Sep. 30, 2011		Dec. 31, 2010		Sep. 30, 2011		Dec. 31, 2010		Sep. 30, 2011		Dec. 31, 2010
Cost of removal obligations	$	403.0	$	395.4	$	260.0	$	257.6	$	143.0	$	137.8
IPL's tax benefit rider		344.3		193.5		344.3		193.5		—		—
IPL's electric transmission assets sale		51.7		71.8		51.7		71.8		—		—
Energy conservation cost recovery		22.4		8.6		1.7		1.7		20.7		6.9
Commodity cost recovery		18.1		12.7		15.9		7.5		2.2		5.2
IPL's Duane Arnold Energy Center (DAEC) sale		15.9		42.3		15.9		42.3		—		—
Tax-related (excl. tax benefit rider)		14.6		16.8		3.6		4.6		11.0		12.2
Emission allowances		1.9		34.4		1.9		33.9		—		0.5
Other		32.1		24.6		18.8		15.0		13.3		9.6
	$	904.0	$	800.1	$	713.8	$	627.9	$	190.2	$	172.2

IPL's tax benefit rider—Alliant Energy's and IPL's "Tax-related" regulatory assets and "IPL's tax benefit rider" regulatory liabilities in the above tables increased significantly during the nine months ended Sep. 30, 2011 due to the impacts of a tax accounting method change for mixed service costs. Refer to Note 4 for additional details of the mixed service costs tax accounting method change.

Pension and other postretirement benefits costs—In May 2011, Alliant Energy, IPL and WPL amended their defined benefit postretirement health care plans, which required a remeasurement of these plans. The remeasurement caused changes in previously unrecognized net actuarial losses and prior service credits for the plans that decreased "Regulatory assets" by $53 million, $35 million and $18 million on Alliant Energy's, IPL's and WPL's Condensed Consolidated Balance Sheets, respectively, during the nine months ended Sep. 30, 2011. Refer to Note 5(a) for additional details of the plan amendment and remeasurement.

Derivatives—In accordance with IPL's and WPL's fuel and natural gas recovery mechanisms, prudently incurred costs from derivative instruments are recovered from customers in the future after any losses are realized and gains from derivative instruments are refunded to customers in the future after any gains are realized. Based on these recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on Alliant Energy's, IPL's and WPL's Condensed Consolidated Balance Sheets during the nine months ended Sep. 30, 2011. Refer to Note 10 for additional details of Alliant Energy's, IPL's and WPL's derivative assets and derivative liabilities.

Emission allowances—

Regulatory assets—IPL entered into forward contracts in 2007 to purchase sulfur dioxide (SO2) emission allowances with vintage years of 2014 through 2017 from various counterparties for $34 million to meet future Clean Air Interstate Rule (CAIR) emission reduction standards. Any SO2 emission allowances acquired under these forward contracts may be used to meet requirements under the existing Acid Rain Program regulations or the more stringent CAIR emission reduction standards. However, any emission allowances acquired under these forward contracts are not eligible to be used for compliance requirements under the Cross-State Air Pollution Rule (CSAPR) issued by the EPA in July 2011, which supersedes existing CAIR compliance requirements effective Jan. 1, 2012. Alliant Energy and IPL have received an allocation of annual Acid Rain allowances from the EPA through 2041. Based on the current forecasted emissions from IPL's generation fleet, the EPA-allocated allowances through 2041 are expected to be more than enough to comply with the Acid Rain program rules. As a result, Alliant Energy and IPL concluded in the third quarter of 2011 that the allowances to be acquired under these forward contracts will not be needed by IPL to comply with Acid Rain Program regulations. The current value of these allowances is nominal, which is significantly below the $34 million contract price for these allowances. As a result, Alliant Energy and IPL recognized charges of $34 million for these forward contracts in the third quarter of 2011. The $34 million obligation was recorded in "Other long-term liabilities and deferred credits" on Alliant Energy's and IPL's Condensed Consolidated Balance Sheets in the third quarter of 2011. Alliant Energy and IPL concluded that $30 million of the charges are probable of recovery from IPL's customers and therefore were recorded to "Regulatory assets" on Alliant Energy's and IPL's Condensed Consolidated Balance Sheets in the third quarter of 2011. The remaining $4 million of charges were determined not to be probable of recovery from IPL's customers resulting in $2 million of charges recorded to "Electric production fuel and energy purchases" and $2 million of charges recorded to "Utility—other operation and maintenance" in Alliant Energy's and IPL's Condensed Consolidated Statements of Income in the third quarter of 2011.

Regulatory liabilities—Refer to Note 13 for discussion of reductions to regulatory liabilities related to emission allowances impairments recorded in the third quarter of 2011 resulting from the EPA's issuance of CSAPR in July 2011.

Proposed base-load projects costs—In accordance with the Minnesota Public Utilities Commission's (MPUC's) August 2011 order related to IPL's 2009 test year Minnesota retail electric rate case, IPL was authorized to recover $2 million of previously incurred plant cancellation costs for its proposed base-load project referred to as Sutherland #4. As a result, Alliant Energy and IPL recorded a $2 million increase to "Regulatory assets" on their Condensed Consolidated Balance Sheets and a $2 million credit to "Utility—other operation and maintenance" on their Condensed Consolidated Statements of Income during the nine months ended Sep. 30, 2011.

IPL's Whispering Willow—East wind project—In accordance with the Iowa Utilities Board's (IUB's) January 2011 order related to IPL's 2009 test year Iowa retail electric rate case, IPL was authorized to utilize $23 million of "IPL's DAEC sale" regulatory liability and $3 million of "IPL's electric transmission assets sale" regulatory liability to offset IPL's Whispering Willow—East wind project plant in service balance. As a result, Alliant Energy and IPL recorded reductions of $26 million in both "Electric plant in service" and "Regulatory liabilities" on their Condensed Consolidated Balance Sheets during the nine months ended Sep. 30, 2011.

IPL's electric transmission assets sale—In accordance with the MPUC's August 2011 order related to IPL's 2009 test year Minnesota retail electric rate case, IPL was authorized to refund a higher amount of the gain realized from the sale of its electric transmission assets in 2007 to its Minnesota retail electric customers than previously estimated. As a result, Alliant Energy and IPL recorded a $5 million increase to "Regulatory liabilities" on their Condensed Consolidated Balance Sheets and a $5 million charge to "Utility—other operation and maintenance" on their Condensed Consolidated Statements of Income during the nine months ended Sep. 30, 2011 for the additional amount to be refunded.

In accordance with the IUB's January 2011 order related to IPL's 2009 test year Iowa retail electric rate case, IPL was authorized to utilize regulatory liabilities in 2011 to offset transmission service expenses related to the Iowa retail portion of 2009 under-recovered costs billed to IPL. As a result, Alliant Energy and IPL recorded reductions of $15 million in "Regulatory liabilities" on their Condensed Consolidated Balance Sheets during the nine months ended Sep. 30, 2011.

Energy conservation cost recovery—WPL collects revenues from its customers to offset certain expenditures incurred by WPL for conservation programs, including state mandated programs and WPL's Shared Savings program. Differences between forecasted costs used to set rates and actual costs for these programs are deferred as a regulatory asset or regulatory liability. During the nine months ended Sep. 30, 2011, WPL's forecasted costs used to set current rates exceeded actual costs for these programs, resulting in a $14 million increase to Alliant Energy's and WPL's "Energy conservation cost recovery" regulatory liability.

Other—Based on an assessment completed during the nine months ended Sep. 30, 2011, Alliant Energy, IPL and WPL recognized impairment charges of $7 million, $2 million and $5 million, respectively, for regulatory assets that are no longer probable of future recovery. The regulatory asset impairment charges were recorded by Alliant Energy, IPL and WPL as reductions in "Regulatory assets" on their Condensed Consolidated Balance Sheets and charges to "Utility—other operation and maintenance" on their Condensed Consolidated Statements of Income during the nine months ended Sep. 30, 2011.

Utility Property, Plant And Equipment

(c) Utility Property, Plant and Equipment -

Franklin County Wind Project—In 2008, Alliant Energy entered into a master supply agreement with Vestas-American Wind Technology, Inc. (Vestas) to purchase 500 MW of wind turbine generator sets and related equipment. Alliant Energy utilized 400 MW of these wind turbine generator sets and related equipment to construct IPL's Whispering Willow—East and WPL's Bent Tree—Phase I wind projects. In the second quarter of 2011, Alliant Energy decided to utilize the remaining 100 MW of wind turbine generator sets and related equipment at Resources to build a non-regulated 100 MW wind project in Iowa, referred to as the Franklin County wind project. In the second quarter of 2011, IPL sold Resources assets for this wind project for $115.3 million, which represented IPL's book value for progress payments to-date for the 100 MW of wind turbine generator sets and related equipment and land rights in Franklin County, Iowa. In addition, Resources assumed the remaining progress payments to Vestas for the 100 MW of wind turbine generator sets and related equipment. The Franklin County wind project is currently expected to be placed into service by the end of 2012. The sale of these wind project assets by IPL to Resources resulted in a decrease in "Utility—other property, plant and equipment" on Alliant Energy's and IPL's Condensed Consolidated Balance Sheets and an increase in "Non-regulated and other—Non-regulated Generation property, plant and equipment" on Alliant Energy's Condensed Consolidated Balance Sheet during the nine months ended Sep. 30, 2011. The proceeds received by IPL were recorded in investing activities in IPL's Condensed Consolidated Statement of Cash Flows during the nine months ended Sep. 30, 2011. IPL utilized the proceeds to reduce outstanding commercial paper and sales of accounts receivable, to invest in various short-term assets, and for general working capital purposes.

WPL's Bent Tree—Phase I Wind Project—In 2009, WPL received approval from the MPUC and PSCW to construct the Bent Tree—Phase I wind project, which began generating electricity in late 2010. WPL incurred capitalized expenditures of $435 million and recognized $14 million of allowance for funds used during construction (AFUDC) for the wind project. In 2010, WPL placed $265 million of the wind project into service. During the nine months ended Sep. 30, 2011, WPL placed the remaining portion of the wind project into service, which resulted in a transfer of $184 million of capitalized project costs from "Construction work in progress—Bent Tree—Phase I wind project" to "Electric plant in service" on Alliant Energy's and WPL's Condensed Consolidated Balance Sheets during the nine months ended Sep. 30, 2011. The capitalized costs for the wind project are being depreciated using a straight-line method of depreciation over a 30-year period.

WPL's Edgewater Unit 5 Emission Controls Project—WPL is currently installing a selective catalytic reduction (SCR) system at Edgewater Unit 5 to reduce nitrogen oxide (NOx) emissions at the generating facility. Construction began in the third quarter of 2010 and is expected to be completed prior to May 2013 when additional NOx emission reductions at Edgewater are required for WPL to comply with Wisconsin Reasonably Available Control Technology (RACT) Rule compliance deadlines. As of Sep. 30, 2011, WPL recorded capitalized expenditures of $60 million and AFUDC of $2 million for the SCR system in "Construction work in progress—Edgewater Generating Station Unit 5 emission controls" on Alliant Energy's and WPL's Condensed Consolidated Balance Sheets.

IPL's Whispering Willow—East Wind Project —In August 2011, IPL received an order from the MPUC approving a temporary recovery rate for the Minnesota retail portion of its Whispering Willow—East wind project construction costs. In its order, the MPUC did not conclude on the prudence of these project costs. The prudence of these project costs and the final recovery rate for these costs will be addressed in a separate proceeding that is expected to be completed in 2012. The initial recovery rate approved by the MPUC is below the amount required by IPL to recover the Minnesota retail portion of its total project costs. Based on its interpretation of the order, IPL currently believes that it is probable it will not be allowed to recover all of the Minnesota retail portion of its project costs. IPL currently believes the most likely outcome of the final rate proceeding will result in the MPUC effectively disallowing recovery of approximately $8 million of project costs out of a total of approximately $30 million of project costs allocated to the Minnesota retail jurisdiction. As a result, IPL recognized an $8 million impairment related to this probable disallowance, which was recorded as a reduction to "Electric plant in service" on Alliant Energy's and IPL's Condensed Consolidated Balance Sheets and a charge to "Utility—other operation and maintenance" in Alliant Energy's and IPL's Consolidated Statements of Income during the nine months ended Sep. 30, 2011. This amount is subject to change until the MPUC determines the final recovery rate for these project costs.

WPL's Green Lake and Fond du Lac Counties Wind Site—In 2009, WPL purchased development rights to an approximate 100 MW wind site in Green Lake and Fond du Lac Counties in Wisconsin. Due to events in the first quarter of 2011 resulting in uncertainty regarding wind siting requirements in Wisconsin and increased risks with permitting this wind site, WPL determined it would be difficult to effectively use the site for wind development. As a result, WPL recognized a $5 million impairment in the first quarter of 2011 for the amount of capitalized costs incurred for this site. The impairment was recorded as a reduction to "Utility—other property, plant and equipment" on Alliant Energy's and WPL's Condensed Consolidated Balance Sheets and a charge to "Utility—other operation and maintenance" in Alliant Energy's and WPL's Condensed Consolidated Statements of Income during the nine months ended Sep. 30, 2011.

WPL's Edgewater Unit 5 Purchase —In March 2011, WPL purchased Wisconsin Electric Power Company's (WEPCO's) 25% ownership interest in Edgewater Unit 5 for $38 million. The $38 million was equal to WEPCO's net book value of the facility and related assets at the time of the purchase. WPL now owns 100% of Edgewater Unit 5. As of the closing date, the carrying values of the assets purchased were as follows (in millions):

Electric plant in service	$	84
Accumulated depreciation		(50	)
Construction work in progress		2
Production fuel		1
Materials and supplies		1
	$	38

Comprehensive Income

(d) Comprehensive Income—Alliant Energy's comprehensive income and the components of other comprehensive income (loss), net of taxes, for the three and nine months ended Sep. 30 were as follows (in millions):

	Three Months						Nine Months
	2011			2010			2011			2010
Net income	$	125.9		$	153.7		$	260.9		$	254.3
Other comprehensive income (loss), net of tax:
Unrealized losses on securities, net of tax		—			(0.2	)		—			(0.4	)
Pension and other postretirement benefits plans adjustments, net of tax		—			0.8			0.8			0.1
Total other comprehensive income (loss)		—			0.6			0.8			(0.3	)
Comprehensive income		125.9			154.3			261.7			254.0
Preferred dividend requirements of subsidiaries		(3.9	)		(4.6	)		(14.3	)		(14.0	)
Comprehensive income attributable to
Alliant Energy common shareowners	$	122.0		$	149.7		$	247.4		$	240.0

For the three and nine months ended Sep. 30, 2011 and 2010, IPL and WPL had no other comprehensive income; therefore their comprehensive income was equal to their earnings available for common stock for such periods.