Summary Of Significant Accounting Policies (Policy)

12 Months Ended

Dec. 31, 2012

Property, Plant and Equipment [Line Items]

The consolidated financial statements reflect investments in controlled subsidiaries on a consolidated basis and Alliant Energy’s, IPL’s and WPL’s proportionate shares of jointly owned utility facilities. Unconsolidated investments, which Alliant Energy and WPL do not control, but do have the ability to exercise significant influence over operating and financial policies, are accounted for under the equity method of accounting. Investments that do not meet the criteria for consolidation or the equity method of accounting are accounted for under the cost method. Alliant Energy, IPL and WPL did not reflect any variable interest entities (VIEs) on a consolidated basis in the consolidated financial statements. Refer to Notes 1(q) and 10(a) for further discussion of VIEs and equity method investments, respectively.

All intercompany balances and transactions, other than certain transactions affecting the rate-making process at IPL and WPL, have been eliminated from the consolidated financial statements. Such transactions not eliminated include costs that are recoverable from customers through rate-making processes.

General, Basis of Accounting

The consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States of America (U.S.) (GAAP), which give recognition to the rate-making and accounting practices of the Federal Energy Regulatory Commission (FERC) and state commissions having regulatory jurisdiction.

General, Reclassification

Certain prior period amounts in the Consolidated Financial Statements and Notes to Consolidated Financial Statements have been reclassified to conform to the current period presentation for comparative purposes. Unless otherwise noted, the notes herein have been revised to exclude discontinued operations and assets and liabilities held for sale for all periods presented.

General, Use of Estimates

Use of Estimates - The preparation of the consolidated financial statements requires management to make estimates and assumptions that affect: (a) the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements; and (b) the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Regulatory Assets and Regulatory Liabilities

Regulatory Assets and Regulatory Liabilities - Alliant Energy, IPL and WPL are subject to regulation by FERC and various state regulatory commissions. As a result, Alliant Energy, IPL and WPL are subject to GAAP provisions for regulated operations, which provide that rate-regulated public utilities record certain costs and credits allowed in the rate-making process in different periods than for non-regulated entities. Regulatory assets generally represent incurred costs that have been deferred as they are probable of recovery in future customer rates. Regulatory liabilities generally represent obligations to make refunds to customers and amounts collected in rates for which the related costs have not yet been incurred. Amounts deferred as regulatory assets or accrued as regulatory liabilities are generally recognized in the Consolidated Statements of Income at the time they are reflected in rates.

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



	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Tax-related		$770.7		$634.7		$746.2		$614.6		$24.5		$20.1
Pension and other postretirement benefits costs	549.2		514.1		279.3		264.9		269.9		249.2
Asset retirement obligations (AROs)	62.4		65.9		38.6		48.7		23.8		17.2
Derivatives	40.2		77.7		16.3		33.5		23.9		44.2
Environmental-related costs	34.9		38.9		30.3		32.2		4.6		6.7
Emission allowances	30.0		30.0		30.0		30.0		—		—
Debt redemption costs	19.8		21.8		13.6		15.1		6.2		6.7
Proposed clean air compliance projects costs	16.7		14.9		7.8		6.9		8.9		8.0
IPL’s electric transmission service costs	16.6		24.9		16.6		24.9		—		—
Proposed coal-fired base-load projects costs	14.2		21.5		10.1		15.3		4.1		6.2
Other	57.7		50.6		29.1		31.2		28.6		19.4
		$1,612.4		$1,495.0		$1,217.9		$1,117.3		$394.5		$377.7

A portion of the regulatory assets in the above table are not earning a return. These regulatory assets are expected to be recovered from customers in future rates, however the respective carrying costs of these assets are not expected to be recovered from customers in future rates. At December 31, 2012, IPL and WPL had $68 million and $13 million, respectively, of regulatory assets representing past expenditures that were not earning a return. IPL’s regulatory assets that were not earning a return consisted primarily of electric transmission service costs, costs for proposed coal-fired base-load and clean air compliance projects, and debt redemption costs. WPL’s regulatory assets that were not earning a return consisted primarily of amounts related to wholesale customer rate recovery. The other regulatory assets reported in the above table either earn a return or the cash has not yet been expended, in which case the assets are offset by liabilities that also do not incur a carrying cost.

Tax-related - IPL and WPL record regulatory assets for certain temporary differences (primarily related to utility property, plant and equipment at IPL) that result in a decrease in current rates charged to customers and an increase in future rates charged to customers based on the timing of income tax expense that is used to determine such rates. These temporary differences include the impact of Iowa accelerated tax depreciation, which contributes to lower current income tax expense during the first part of an asset’s useful life and higher current tax expense during the last part of an asset’s useful life. These regulatory assets will be recovered from customers in the future when these temporary differences reverse resulting in additional current income tax expense used to determine customers’ rates. During 2012, Alliant Energy’s and IPL’s “Tax-related” regulatory assets in the above table increased primarily due to changes in the estimated amount of qualifying repair expenditures and allocation of mixed service costs at IPL.

Pension and other postretirement benefits costs - The Iowa Utilities Board (IUB) and the Public Service Commission of Wisconsin (PSCW) have authorized IPL and WPL to record the retail portion of their respective previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets in lieu of accumulated other comprehensive loss (AOCL) on the Consolidated Balance Sheets, as these amounts are expected to be recovered in future rates. IPL and WPL also recognize the wholesale portion of their previously unrecognized net actuarial gains and losses, and prior service costs and credits, as regulatory assets on the Consolidated Balance Sheets because these costs are expected to be recovered in rates in future periods under the formula rate structure. These regulatory assets will be increased or decreased as the net actuarial gains or losses, and prior service costs or credits, are subsequently amortized and recognized as a component of net periodic benefit costs.

Pension and other postretirement benefits costs are included within the recoverable cost of service component of rates charged to IPL’s and WPL’s customers. The recoverable costs included in customers’ rates are based upon pension and other postretirement benefits costs determined in accordance with GAAP and are calculated using different methods for the various regulatory jurisdictions in which IPL and WPL operate. The methods for IPL’s and WPL’s primary regulatory jurisdictions are described below. The IUB authorized IPL in its most recent Iowa retail electric rate case order to recover from its retail electric customers in Iowa an allocated portion of annual costs equal to a two-year simple average of actual costs incurred during its test year (2009) and an estimate of costs for its forward-looking post-test year (2010). The PSCW authorized WPL to recover from its electric and gas retail customers in base rates an estimated allocated portion of annual costs equal to the costs expected to be incurred during the 2013 and 2014 rate freeze period. WPL is authorized to recover from its wholesale customers an allocated portion of actual pension costs incurred each year. In accordance with FERC-approved formula rates, any over- or under-collection of these costs each year are refunded to or recovered from customers through subsequent changes to wholesale customer rates. WPL is authorized to recover from its wholesale customers an allocated portion of other postretirement benefits costs based on the amount of other postretirement benefits costs incurred in 2006. Refer to Note 6(a) for additional details regarding pension and other postretirement benefits costs.

AROs - Alliant Energy, IPL and WPL believe it is probable that any differences between expenses accrued for legal AROs related to their regulated operations and expenses recovered currently in rates will be recoverable in future rates, and are deferring the differences as regulatory assets. The decrease in IPL’s regulatory assets related to AROs is primarily due to revisions in estimated cash flows based on revised remediation timing and cost information for asbestos remediation at Sixth Street. The increase in WPL’s regulatory assets related to AROs is primarily due to revisions in estimated cash flows based on revised remediation timing and cost information for remediation of the coal yard and ash pond at Rock River. Refer to Note 18 for additional details of AROs.

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 the Consolidated Balance Sheets. Refer to Note 12 for additional details of derivative assets and derivative liabilities.

Environmental-related costs - The IUB has permitted IPL to recover prudently incurred costs by allowing a representative level of manufactured gas plant (MGP) costs in the recoverable cost of service component of rates, as determined in its most recent retail gas rate case. Under the current rate-making treatment approved by the PSCW, the MGP expenditures of WPL are deferred and collected from retail gas customers over a five-year period after new rates are implemented. The Minnesota Public Utilities Commission (MPUC) allows the deferral of MGP-related costs applicable to IPL’s Minnesota sites and IPL has received approval to recover such costs in retail gas rates in Minnesota in its most recent retail gas rate case. Regulatory assets recorded by IPL and WPL reflect the probable future rate recovery of MGP expenditures. Refer to Note 13(e) for additional details of environmental-related MGP costs.

Emission allowances - 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 but are not eligible to be used for compliance requirements under the Cross-State Air Pollution Rule (CSAPR). In 2011, the U.S. Environmental Protection Agency (EPA) issued CSAPR to replace CAIR with an anticipated effective date in 2012. As a result of the issuance of CSAPR, Alliant Energy and IPL concluded in 2011 that the allowances to be acquired under these forward contracts would not be needed by IPL to comply with expected environmental regulations in the future. The value of these allowances was nominal, which was 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 2011 with an offsetting obligation recorded in other long-term liabilities and deferred credits. 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 in 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 related to electric customers recorded to “Electric production fuel and energy purchases” and $2 million of charges related to steam customers recorded to “Utility - Other operation and maintenance” in Alliant Energy’s and IPL’s Consolidated Statements of Income in 2011. In August 2012, the U.S. Court of Appeals for the D.C. Circuit (D.C. Circuit Court) vacated and remanded CSAPR for further revision to the EPA. The D.C. Circuit Court order also requires the EPA to continue administering CAIR pending the promulgation of a valid replacement for CSAPR. Despite CSAPR being vacated, the current value of these allowances continues to be nominal and significantly below the $34 million contract price for these allowances. Alliant Energy and IPL currently believe that CAIR will be replaced in the future, either by a modified CSAPR or another rule that addresses the interstate transport of air pollutants.

Debt redemption costs - For debt retired early with no subsequent re-issuance, IPL and WPL defer any debt repayment premiums and unamortized debt issuance costs and discounts as regulatory assets. These regulatory assets are amortized over the remaining original life of the debt retired early. Debt repayment premiums and other losses resulting from the refinancing of debt by IPL and WPL are deferred as regulatory assets and amortized over the life of the new debt issued.

Proposed clean air compliance plan (CACP) projects costs - CACP projects require material expenditures for activities related to determining the feasibility of environmental compliance projects under consideration. These expenditures are commonly referred to as preliminary survey and investigation charges. The wholesale portion of these amounts is recorded as regulatory assets on the Consolidated Balance Sheets in accordance with FERC regulations. In Iowa, no specific retail authorization is required before charging these costs to regulatory asset accounts. In Wisconsin, the retail portion of these amounts is expensed immediately unless otherwise authorized by the PSCW. However, since these amounts are material for WPL’s CACP projects, WPL requested and received deferral accounting approval to record the retail portion of these costs as regulatory assets on the Consolidated Balance Sheets.

For IPL, amounts deferred and recorded as preliminary survey and investigation charges do not include any accrual of carrying costs or allowance for funds used during construction (AFUDC). Upon management’s decision to proceed with a project, including receipt of certain regulatory approvals, all such amounts included as preliminary survey and investigation charges are transferred to construction work in progress (CWIP) and begin to accrue AFUDC.

For WPL, the wholesale portion of amounts deferred and recorded as preliminary survey and investigation charges do not include any accrual of carrying costs or AFUDC. WPL’s retail portion of deferred preliminary survey and investigation charges (commonly referred to as pre-certification expenditures) and construction expenditures incurred prior to project approval that are recorded in regulatory assets include accrual of carrying costs as prescribed in the approved deferral order. Upon regulatory approval of the project, the wholesale portion of deferred preliminary survey and investigation charges as well as all pre-construction expenditures are transferred to CWIP and begin to accrue AFUDC. The retail portion of deferred preliminary survey and investigation charges or pre-certification expenditures remain as regulatory assets until they are approved for inclusion in revenue requirements and amortized to expense.

Alliant Energy, IPL and WPL anticipate the remaining costs for proposed CACP projects are probable of recovery from future rates charged to customers. The recovery period for these remaining costs will generally be determined by regulators in future rate proceedings.

IPL’s electric transmission service costs - In 2010, IPL incurred electric transmission service costs billed by ITC Midwest LLC (ITC) under the Attachment “O” rate for ITC’s under-recovered 2008 costs. In 2010, the IUB issued an order authorizing IPL to defer the Iowa retail portion of these under-recovered costs and amortize the deferred costs over a 5-year period ending December 2014. In accordance with this order, IPL is amortizing $8 million of this regulatory asset annually, with an equal and offsetting amount of amortization of IPL’s regulatory liability related to its electric transmission assets sale. The IUB determined that IPL should not include the unamortized balance of these deferred costs in electric rate base during the 5-year recovery period. The IUB also authorized IPL to use up to $46 million of regulatory liabilities from its 2007 electric transmission assets sale to offset these deferred costs as they are amortized. In 2010, $41 million (portion allocated to Iowa retail customers) of the Attachment “O” costs were deferred by IPL and recognized as a regulatory asset.

Proposed coal-fired base-load projects costs -

IPL’s coal-fired base-load project - In 2009, IPL announced a decision to cancel the construction of the proposed 630 MW coal-fired electric generating facility in Marshalltown, Iowa referred to as Sutherland #4. In 2010, IPL received approval from the IUB to recover $26 million of the costs incurred for Sutherland #4 from its retail customers in Iowa by amortizing the costs over a 5-year period ending August 2014. In accordance with this approval, IPL is amortizing $5 million of this regulatory asset annually, with an equal and offsetting amount of amortization of IPL’s regulatory liability resulting from the sale of the Duane Arnold Energy Center (DAEC). The IUB determined that IPL should not include the unamortized balance of these Sutherland #4 costs in electric rate base during the 5-year recovery period.

In accordance with the MPUC’s November 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 Sutherland #4 over a 25-year period ending in 2037. As a result, Alliant Energy and IPL recorded a $2 million increase to regulatory assets, and a $2 million credit to “Utility - Other operation and maintenance” in their Consolidated Statements of Income in 2011.

WPL’s coal-fired base-load project - In 2008, the PSCW issued an order denying WPL’s application to construct a 300 MW coal-fired electric generating facility in Cassville, Wisconsin referred to as Nelson Dewey #3. In 2009, WPL received approval from the PSCW to recover $11 million of project costs from its retail customers over a 5-year period ending December 2014. In accordance with this approval, WPL is amortizing $2 million of this regulatory asset annually.

Other - Alliant Energy, IPL and WPL assess whether IPL’s and WPL’s regulatory assets are probable of future recovery by considering factors such as applicable regulations, recent orders by the applicable regulatory agencies, historical treatment of similar costs by the applicable regulatory agencies and regulatory environment changes. Based on these assessments, Alliant Energy, IPL and WPL believe the regulatory assets recognized as of December 31, 2012 in the above table are probable of future recovery. However, no assurance can be made that IPL and WPL will recover all of these regulatory assets in future rates. If future recovery of a regulatory asset ceases to be probable, the regulatory asset will be charged to expense in the period in which future recovery ceases to be probable. Based on assessments completed in 2011, Alliant Energy, IPL and WPL recognized impairment charges of $9 million, $2 million and $7 million, respectively, for regulatory assets that were no longer probable of future recovery. The regulatory asset impairment charges were recorded by Alliant Energy, IPL and WPL as reductions in regulatory assets and charges to “Utility - Other operation and maintenance” in their Consolidated Statements of Income in 2011.

Based on the PSCW’s July 2012 order related to WPL’s 2013/2014 test period Wisconsin retail electric and gas rate case, WPL was authorized to recover previously incurred costs associated with the acquisition of a 25% ownership interest in Edgewater Unit 5 and proposed CACP projects. As a result, Alliant Energy and WPL recorded a $5 million increase to “Regulatory assets” on their Consolidated Balance Sheets and a $5 million credit to “Utility - Other operation and maintenance” in their Consolidated Statements of Income in 2012.

Based on the IUB’s February 2011 order related to IPL’s 2009 test year Iowa retail electric rate case, IPL was authorized to recover from its retail electric customers in Iowa operation and maintenance expenses incurred in 2009 for restoration activities from severe flooding in IPL’s service territory. As a result, Alliant Energy and IPL recorded a $7 million regulatory asset in 2010 with an offsetting pre-tax regulatory-related credit of $7 million in “Utility - Other operation and maintenance” in their Consolidated Statements of Income in 2010. In addition, the IUB’s February 2011 order also authorized IPL to recover from its retail electric customers in Iowa a portion of the remaining net book value of Sixth Street and previously impaired CWIP assets related to Sixth Street, which was shut down as a result of the flooding. As a result, Alliant Energy and IPL recorded a $16 million regulatory asset in 2010 with an offsetting increase of $14 million in utility accumulated depreciation and a credit of $2 million in “Utility - Other operation and maintenance” in their Consolidated Statements of Income in 2010.

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



	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Cost of removal obligations		$408.7		$404.9		$268.0		$261.9		$140.7		$143.0
IPL’s tax benefit riders	355.8		349.6		355.8		349.6		—		—
Energy conservation cost recovery	55.1		29.6		10.0		4.7		45.1		24.9
IPL’s electric transmission assets sale	32.5		45.1		32.5		45.1		—		—
Commodity cost recovery	17.7		23.8		5.2		23.2		12.5		0.6
IPL’s DAEC sale	9.5		14.6		9.5		14.6		—		—
Other	36.8		42.5		20.4		22.2		16.4		20.3
		$916.1		$910.1		$701.4		$721.3		$214.7		$188.8

Regulatory liabilities related to cost of removal obligations, to the extent expensed through depreciation rates, reduce rate base. A significant portion of the remaining regulatory liabilities are not used to reduce rate base in the revenue requirement calculations utilized in IPL’s and WPL’s respective rate proceedings.

Cost of removal obligations - Alliant Energy, IPL and WPL collect in rates future removal costs for many assets that do not have associated legal AROs. Alliant Energy, IPL and WPL record a regulatory liability for the estimated amounts they have collected in rates for these future removal costs less amounts spent on removal activities.

IPL’s tax benefit riders - Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities in the above table increased primarily due to changes in the estimated amounts of qualifying repair expenditures and allocation of mixed service costs at IPL. These items were offset by regulatory liabilities used to credit IPL’s Iowa retail electric customers’ bills in 2012. In January 2011, the IUB approved IPL’s proposed electric tax benefit rider, which utilizes tax-related regulatory liabilities related to projected tax benefits from tax accounting methodologies and tax elections available under the Internal Revenue Code to credit IPL’s retail electric customer bills in Iowa during 2011, 2012 and 2013. 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. In 2012 and 2011, Alliant Energy and IPL utilized $83 million and $61 million, respectively, of electric tax benefit rider-related regulatory liabilities accumulated in prior years to credit IPL’s Iowa retail electric customers’ bills. In 2012 and 2011, the $83 million and $61 million reductions to “Electric operating revenues” resulted in $35 million and $25 million of credits to “Income tax expense (benefit)” as a result of the decrease in taxable income in Alliant Energy’s and IPL’s Consolidated Statements of Income in 2012 and 2011, respectively. In 2012 and 2011, additional reductions to “Income tax expense (benefit)” of $48 million and $36 million, respectively, were also recognized in Alliant Energy’s and IPL’s Consolidated Statements of Income representing the tax benefits realized related to the electric tax benefit rider.

In December 2012, the IUB issued an order authorizing $56 million of regulatory liabilities from tax benefits to be credited to IPL’s retail electric customers’ bills in Iowa during 2013 through the electric tax benefit rider. In November 2012, the IUB issued an order authorizing $12 million of regulatory liabilities from tax benefits to be credited to IPL’s retail gas customers’ bills in Iowa during 2013 through a gas tax benefit rider. In February 2013, the IUB issued an order authorizing IPL to utilize $24 million of regulatory liabilities during 2013 from tax benefits for the electric tax benefit rider to recognize the revenue requirement impact of the changes in tax accounting methods. Refer to Note 2 for discussion of the gas tax benefit rider for IPL’s Iowa retail gas customers and Note 5 for additional details regarding the tax benefit rider for IPL’s Iowa retail electric customers.

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. In 2012, WPL’s forecasted costs used to set current rates exceeded actual costs for these programs, resulting in the increase to Alliant Energy’s and WPL’s “Energy conservation cost recovery” regulatory liability.

IPL electric transmission assets sale - In 2007, IPL completed the sale of its electric transmission assets to ITC and recognized a gain based on the terms of the agreement. Upon closing of the sale, IPL established a regulatory liability of $89 million pursuant to conditions established by the IUB when it allowed the transaction to proceed. The regulatory liability represented the present value of IPL’s obligation to refund to its customers payments beginning in the year IPL’s customers experience an increase in rates related to the transmission charges assessed by ITC. The regulatory liability accrues interest at the monthly average U.S. Treasury rate for three-year maturities.

Iowa retail portion - In 2009, the IUB issued an order authorizing IPL to use a portion of this regulatory liability to reduce Iowa retail electric customers’ rates by $12 million for the period from July 2009 through February 2010 with billing credits included in the monthly energy adjustment clause. In 2010, the IUB issued an order authorizing IPL to use up to $46 million of this regulatory liability to offset electric transmission service costs expected to be billed to IPL by ITC in 2010 related to ITC’s 2008 transmission revenue adjustment. IPL expects to utilize $41 million of this regulatory liability over a 5-year period ending December 2014 to offset the Iowa retail portion of transmission costs billed to IPL by ITC in 2010 related to ITC’s 2008 transmission revenue adjustment. As a result, IPL is amortizing $8 million of this regulatory liability annually, with an equal and offsetting amount of amortization for IPL’s regulatory asset related to electric transmission service costs.

In accordance with the IUB’s 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 a reduction of $19 million in regulatory liabilities, and a reduction of $19 million in “Electric transmission service” in their Consolidated Statements of Income in 2011. The IUB also authorized IPL to utilize $3 million of this regulatory liability in 2011 to reduce IPL’s Iowa retail electric rate base associated with the Whispering Willow - East wind project.

Minnesota retail portion - In 2010, the MPUC issued an interim rate order authorizing IPL to use a portion of this regulatory liability to implement an alternative transaction adjustment through its energy adjustment clause resulting in annual credits to its Minnesota retail electric customers beginning in July 2010 to coincide with the effective date of the interim rate increase for Minnesota retail customers. The amounts of the annual credits are dependent upon the level of kilowatt-hours sold to IPL’s Minnesota retail customers. In accordance with the MPUC’s November 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, and a $5 million charge to “Utility - Other operation and maintenance” in their Consolidated Statements of Income in 2011 for the additional amount to be refunded.

Refunds related to any remaining balance of IPL’s electric transmission assets sale regulatory liability are expected to be determined in future rate proceedings.

Commodity cost recovery - Refer to Note 1(h) for additional details of IPL’s and WPL’s cost recovery mechanisms. Refer to Note 2 for discussion of certain rate refund reserves recorded as regulatory liabilities on the Consolidated Balance Sheets.

IPL’s DAEC sale - In 2006, IPL completed the sale of its 70% ownership interest in DAEC and recognized a regulatory liability of approximately $59 million from the transaction based on the terms of the sale agreement. Pursuant to the IUB order approving the DAEC sale, the gain resulting from the sale was used to establish a regulatory liability. In 2009, IPL received $12 million as part of a settlement of a claim filed against the U.S. Department of Energy (DOE) in 2004 for recovery of damages due to the DOE’s delay in accepting spent nuclear fuel produced at DAEC. IPL recognized the $12 million received from the settlement as an increase to the regulatory liability established with the sale of DAEC. The regulatory liability accrues interest at the monthly average U.S. Treasury rate for three-year maturities.

In 2009, the IUB authorized IPL to utilize $29 million of this regulatory liability to reduce electric plant in service in 2009 related to the cumulative AFUDC recognized for the Whispering Willow - East wind project. In 2010, IPL received approval from the IUB to utilize $26 million of this regulatory liability to offset the amortization of costs incurred for the Sutherland #4 project over a 5-year period ending August 2014. As a result, IPL is amortizing $5 million of this regulatory liability annually, with an equal and offsetting amount of amortization for IPL’s regulatory asset related to the Sutherland #4 project. In 2011, the IUB authorized IPL to utilize $23 million of this regulatory liability to reduce IPL’s Iowa retail electric rate base in 2011 for the Whispering Willow - East wind project.

Refunds related to any remaining balance of IPL’s DAEC sale regulatory liability are expected to be determined in future rate proceedings.

Income Taxes

Income Taxes - Alliant Energy, IPL and WPL follow the liability method of accounting for deferred income taxes, which requires the establishment of deferred income tax assets and liabilities, as appropriate, for temporary differences between the tax basis of assets and liabilities and the amounts reported in the consolidated financial statements. Deferred income taxes are recorded using currently enacted tax rates and estimates of state apportionment rates. Changes in deferred income tax assets and liabilities associated with certain property-related differences at IPL are accounted for differently than other subsidiaries of Alliant Energy due to rate-making practices in Iowa. Rate-making practices in Iowa do not include the impact of certain deferred tax expenses (benefits) in the determination of retail rates. Based on these rate-making practices, deferred tax expense (benefit) related to these property-related differences at IPL is not recorded in the income statement but instead charged to regulatory assets or regulatory liabilities until these temporary differences are reversed. Refer to Note 1(b) for further discussion of regulatory assets and regulatory liabilities associated with property-related differences at IPL. In Wisconsin, the PSCW has allowed rate recovery of deferred taxes on all temporary differences since 1991.

Alliant Energy, IPL and WPL recognize positions taken, or expected to be taken, in income tax returns that are more-likely-than-not to be realized, assuming that the position will be examined by tax authorities with full knowledge of all relevant information. If it is more-likely-than-not that a tax position, or some portion thereof, will not be sustained, the related tax benefits are not recognized in the consolidated financial statements. Uncertain tax positions may result in an increase in income taxes payable, a reduction of income tax refunds receivable or changes in deferred taxes. Also, when uncertainty about the deductibility of an amount is limited to the timing of such deductibility, the increase in taxes payable (or reduction in tax refunds receivable) is accompanied by a decrease in deferred tax liabilities. Generally Alliant Energy, IPL and WPL recognize current taxes payable related to uncertain tax positions in “Accrued taxes” and non-current taxes payable related to uncertain tax positions in “Other long-term liabilities and deferred credits” on the Consolidated Balance Sheets. However, if the uncertain tax position would be settled through the reduction of a net operating loss rather than through the payment of cash, the uncertain tax position is reflected in “Deferred income taxes” on the Consolidated Balance Sheets. Refer to Note 5 for further discussion of uncertain tax positions.

Alliant Energy, IPL and WPL defer investment tax credits and amortize the credits to income over the average lives of the related property. Other tax credits for Alliant Energy, IPL and WPL reduce income tax expense in the year claimed.

Alliant Energy, IPL and WPL have elected the alternative transition method to calculate their beginning pool of excess tax benefits available to absorb any tax deficiencies associated with recognition of share-based payment awards.

Alliant Energy files a consolidated federal income tax return, which includes the aggregate taxable income or loss of Alliant Energy and its subsidiaries. In addition, a combined return including Alliant Energy and all of its subsidiaries is filed in Wisconsin. Alliant Energy subsidiaries with a presence in Iowa file as part of a consolidated return in Iowa. Under the terms of a tax sharing agreement between Alliant Energy and its subsidiaries, the subsidiaries calculate state income tax using consolidated apportionment rates applied to separate company taxable income.

Cash and Cash Equivalents

Cash and Cash Equivalents - Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days.

Depreciation

Depreciation - IPL and WPL use a combination of remaining life and straight-line depreciation methods as approved by their respective regulatory commissions. The composite or group method of depreciation is used, in which a single depreciation rate is applied to the gross investment in a particular class of property. This method pools similar assets and then depreciates each group as a whole. Periodic depreciation studies are performed to determine the appropriate group lives, net salvage, estimated cost of removal and group depreciation rates. These depreciation studies are subject to review and approval by IPL’s and WPL’s respective regulatory commissions. Depreciation expense is included within the recoverable cost of service component of rates charged to customers.

AFUDC

AFUDC - AFUDC represents costs to finance construction additions including a return on equity component and cost of debt component as required by regulatory accounting. The concurrent credit for the amount of AFUDC capitalized is recorded as “Allowance for funds used during construction” in the Consolidated Statements of Income. The amount of AFUDC generated by equity and debt components was as follows (in millions):



	Alliant Energy						IPL						WPL
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Equity		$14.1		$7.6		$11.2		$5.2		$3.5		$3.0		$8.9		$4.1		$8.2
Debt	7.8		4.4		6.8		3.2		2.3		2.5		4.6		2.1		4.3
		$21.9		$12.0		$18.0		$8.4		$5.8		$5.5		$13.5		$6.2		$12.5

WPL recognized $11 million and $3 million of AFUDC in 2012 and 2011, respectively, for its Edgewater Unit 5 and Columbia Units 1 and 2 emission controls projects. WPL recognized $1 million and $10 million of AFUDC in 2011 and 2010, respectively, for its Bent Tree - Phase I wind project, a portion of which was placed in service in 2010 and 2011.

AFUDC for IPL’s construction projects is calculated in accordance with FERC guidelines. AFUDC for WPL’s retail and wholesale jurisdiction construction projects is calculated in accordance with PSCW and FERC guidelines, respectively. The AFUDC recovery rates, computed in accordance with the prescribed regulatory formula, were as follows:



	2012	2011	2010
IPL (FERC formula)	8.2%	8.5%	4.8%
WPL (PSCW formula - retail jurisdiction) (a)	8.8%	8.8%	8.8%
WPL (FERC formula - wholesale jurisdiction)	7.9%	6.2%	7.2%

(a)

Consistent with the PSCW’s retail rate case order issued in 2009, WPL earned a current return on 50% of the estimated CWIP related to its Bent Tree - Phase I wind project for 2010 and accrued AFUDC on the remaining 50% in 2010. Consistent with the PSCW’s retail order issued in 2009, WPL accrued AFUDC on 100% of CWIP related to the Edgewater Unit 5 emission controls project and the Columbia Units 1 and 2 emission controls project in 2012, 2011 and 2010. Consistent with the PSCW’s retail rate case order issued in 2012, WPL will earn a return on 50% of the estimated CWIP related to its Columbia Units 1 and 2 emission controls project for 2013 and will accrue AFUDC on the remaining 50% in 2013.

Operating Revenues

Operating Revenues -

Utility - Revenues from Alliant Energy’s utility business are primarily from electricity and natural gas sales and are recognized on an accrual basis as services are rendered or commodities are delivered to customers. Energy sales to individual customers are based on the reading of customers’ meters, which occurs on a systematic basis throughout each reporting period. Amounts of energy delivered to customers since the date of the last meter reading are estimated at the end of each reporting period and the corresponding estimated unbilled revenue is recorded. The unbilled revenue estimate is based on daily system demand volumes, estimated customer usage by class, weather impacts, line losses and the most recent customer rates.

IPL and WPL accrue revenues from their wholesale customers to the extent that the actual net revenue requirements calculated in accordance with FERC-approved formula rates for the reporting period are higher than the amounts billed to wholesale customers during such period. In accordance with authoritative guidance, regulatory assets are recorded as the offset for these accrued revenues under formulaic rate-making programs. IPL’s estimated recovery amount is recorded in the current period of service and is reflected in customer bills within two years under the provisions of approved formula rates. WPL’s estimated recovery amount is recorded in the current period of service and subject to final adjustments after a customer audit period in the subsequent year. Final settled recovery amounts are reflected in WPL’s customer bills within two years under the provisions of approved formula rates.

IPL and WPL participate in bid/offer-based wholesale energy and ancillary services markets operated by the Midwest Independent Transmission System Operator (MISO). IPL’s and WPL’s customers and generating resources are located in the MISO region. MISO requires that all load serving entities and generation owners, including IPL and WPL, submit hourly day-ahead and/or real-time bids and offers for energy and ancillary services. The MISO day-ahead and real-time transactions are grouped together, resulting in a net supply to or net purchase from MISO of megawatt-hours (MWhs) for each hour of each day. The net supply to MISO is recorded in “Electric utility operating revenues” and the net purchase from MISO is recorded in “Electric production fuel and energy purchases” in the Consolidated Statements of Income. IPL and WPL also engage in transactions in PJM Interconnection, LLC’s bid/offer-based wholesale energy market, which are accounted for similar to the MISO transactions.

Non-regulated - Revenues from Alliant Energy’s non-regulated businesses are primarily from its Transportation business and are recognized on an accrual basis as services are rendered or goods are delivered to customers.

Taxes Collected from Customers - Certain of Alliant Energy’s subsidiaries serve as collection agents for sales or various other taxes and record revenues on a net basis. Operating revenues do not include the collection of the aforementioned taxes.

Utility Cost Recovery Mechanisms

Utility Cost Recovery Mechanisms -

Electric Production Fuel and Energy Purchases (Fuel-related Costs) - Alliant Energy, IPL and WPL incur fuel-related costs each period to generate and purchase electricity to meet the demand of their electric customers. These fuel-related costs include the cost of fossil fuels (primarily coal and natural gas) used during each period to produce electricity at their generating facilities, electricity purchased each period from wholesale energy markets (primarily MISO) and under PPAs, costs for allowances acquired to allow certain emissions (primarily SO2 and NOx) from their generating facilities and costs for chemicals utilized to control emissions from their generating facilities. Alliant Energy, IPL and WPL record these fuel-related costs in “Electric production fuel and energy purchases” in the Consolidated Statements of Income.

IPL Retail - The cost recovery mechanisms applicable for IPL’s retail electric customers provide for subsequent adjustments to their electric rates for changes in electric production fuel and purchased energy costs. Fuel adjustment clause rules applicable to IPL’s Iowa retail jurisdiction also currently allow IPL to recover prudently incurred costs for emission allowances required to comply with EPA regulations including the Acid Rain program and CAIR through the fuel adjustment clause. Changes in the under-/over-collection of these costs each period are recognized in “Electric production fuel and energy purchases” in Alliant Energy’s and IPL’s Consolidated Statements of Income. The cumulative effects of the under-/over-collection of these costs are recorded in current “Regulatory assets” or current “Regulatory liabilities” on Alliant Energy’s and IPL’s Consolidated Balance Sheets until they are reflected in future billings to customers. The fuel adjustment clause rules applicable to IPL’s Iowa retail jurisdiction currently do not contain a provision for recovery of emission control chemical costs to flow through the fuel adjustment clause. The fuel adjustment clause rules applicable to IPL’s Minnesota retail jurisdiction currently do not contain a provision for recovery of emission allowance costs or emission control chemical costs through the fuel adjustment clause.

WPL Retail - The cost recovery mechanism applicable for WPL’s retail electric customers was changed effective January 2011. For periods prior to 2011, WPL’s retail electric rates approved by the PSCW were based on forecasts of forward-looking test periods and included estimates of future electric production fuel and purchased energy costs anticipated during the test period. During each electric retail rate proceeding, the PSCW set fuel monitoring ranges based on the forecasted electric production fuel and purchased energy costs used to determine retail base rates. If WPL’s actual electric production fuel and purchased energy costs fell outside these fuel monitoring ranges during the test period, WPL and/or other parties could request, and the PSCW could authorize, an adjustment to future retail electric rates based on changes in electric production fuel and purchased energy costs only. The PSCW could also authorize an interim retail rate increase. However, if the final retail rate increase was less than the monitoring range threshold required to be met in order to request interim rate relief, all interim rates collected would be subject to refund to WPL’s retail customers with interest at the current authorized return on common equity rate. In addition, if the final retail rate increase was less than the interim retail rate increase, WPL must refund any excess collections above the final rate increase to its retail customers with interest at the current authorized return on common equity rate.

For periods after 2010, the cost recovery mechanism applicable for WPL’s retail electric customers continues to be based on forecasts of certain fuel-related costs expected to be incurred during forward-looking test year periods and fuel monitoring ranges determined by the PSCW during each electric retail rate proceeding or in a separate fuel cost plan approval proceeding. However, under the post-2010 cost recovery mechanism, if WPL’s actual fuel-related costs fall outside these fuel monitoring ranges during the test period, WPL is authorized to defer the incremental under-/over-collection of fuel costs that are outside the approved ranges. Deferral of under-collections are reduced to the extent actual return on common equity earned by WPL during the fuel cost plan year exceeds the most recently authorized return on common equity. Such deferred amounts are recognized in “Electric production fuel and energy purchases” in Alliant Energy’s and WPL’s Consolidated Statements of Income each period. The cumulative effects of these deferred amounts are recorded in current “Regulatory assets” or current “Regulatory liabilities” on Alliant Energy’s and WPL’s Consolidated Balance Sheets until they are reflected in future billings to customers. Effective January 2012, WPL’s retail fuel-related costs include costs for emission allowances and emission control chemicals. Prior to 2012, WPL’s retail fuel-related costs excluded costs for emission allowances and emission control chemicals.

IPL and WPL Wholesale - The cost recovery mechanisms applicable for IPL’s and WPL’s wholesale electric customers provide for subsequent adjustments to their electric rates for changes in electric production fuel and purchased energy costs. Changes in the under-/over-collection of these costs are recognized in “Electric production fuel and energy purchases” in the Consolidated Statements of Income each period. The cumulative effects of the under-/over-collection of these costs are recorded in current “Regulatory assets” or current “Regulatory liabilities” on the Consolidated Balance Sheets until they are reflected in future billings to customers. IPL’s and WPL’s costs for emission allowances and emission control chemicals are recovered through the capacity charge component of their respective wholesale formula rates.

Purchased Electric Capacity - Alliant Energy, IPL and WPL enter into PPAs to help meet the electricity demand of their customers. Certain of these PPAs include minimum payments for IPL’s and WPL’s rights to electric generating capacity, which are charged each period to “Purchased electric capacity” in the Consolidated Statements of Income. Purchased electric capacity expenses are recovered from IPL’s and WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Purchased electric capacity expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure.

Electric Transmission Service - Alliant Energy, IPL and WPL incur costs for the transmission of electricity to their customers and charge these costs each period to “Electric transmission service” in the Consolidated Statements of Income. Electric transmission service expenses are recovered from WPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. Electric transmission service expenses are recovered from IPL’s and WPL’s wholesale electric customers through annual changes in base rates determined by a formula rate structure.

Prior to 2011, electric transmission service expenses were recovered from IPL’s retail electric customers through changes in base rates determined during periodic rate proceedings. In January 2011, the IUB approved IPL’s proposal to implement a transmission cost rider for recovery of electric transmission service expenses with certain conditions. The IUB stipulated that the rider would be implemented on a pilot basis conditional upon IPL’s agreement to not file an electric base rate case for three years from the date of the order and meet additional reporting requirements. In January 2011, IPL accepted the transmission cost rider with the IUB’s conditions. Effective February 2011, electric transmission service expenses were removed from base rates and billed to IPL’s Iowa electric retail customers through the transmission cost rider. This new cost recovery mechanism provides for subsequent adjustments to electric rates charged to Iowa electric retail customers for changes in electric transmission service expenses. Changes in the under-/over-collection of these costs each period are recognized in “Electric transmission service” in Alliant Energy’s and IPL’s Consolidated Statements of Income. The cumulative effects of the under-/over-collection of these costs are recorded in current “Regulatory assets” or current “Regulatory liabilities” on Alliant Energy’s and IPL’s Consolidated Balance Sheets until they are reflected in future billings to customers.

Cost of Gas Sold - Alliant Energy, IPL and WPL incur costs for the purchase, transportation and storage of natural gas to serve their gas customers and charge the costs associated with the natural gas delivered to customers during each period to “Cost of gas sold” in the Consolidated Statements of Income. The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates for changes in the cost of gas sold. Changes in the under-/over-collection of these costs are also recognized in “Cost of gas sold” in the Consolidated Statements of Income. The cumulative effects of the under-/over-collection of these costs are recorded in current “Regulatory assets” or current “Regulatory liabilities” on the Consolidated Balance Sheets until they are reflected in future billings to customers.

Energy Efficiency Costs - Alliant Energy, IPL and WPL incur costs to fund energy efficiency programs and initiatives that help customers reduce their energy usage and charge these costs incurred each period to “Utility - Other operation and maintenance” in the Consolidated Statements of Income. Energy efficiency costs incurred by IPL are recovered from its retail electric and gas customers in Iowa through an additional tariff called an energy efficiency cost recovery (EECR) factor. EECR factors are revised annually and include a reconciliation to eliminate any under-/over-collection of energy efficiency costs from prior periods. Energy efficiency costs incurred by WPL are recovered from retail electric and gas customers through changes in base rates determined during periodic rate proceedings. Reconciliation of any under-/over-collection of energy efficiency costs from prior periods are also addressed in periodic rate proceedings. Changes in the under-/over-collection of energy efficiency costs each period are recognized in “Utility - Other operation and maintenance” in the Consolidated Statements of Income. The cumulative effects of the under-/over-collection of these costs are recorded in current “Regulatory assets” or current “Regulatory liabilities” on the Consolidated Balance Sheets until they are reflected in future billings to customers.

Financial Instruments

Financial Instruments - Alliant Energy, IPL and WPL periodically use financial instruments for risk management purposes to mitigate exposures to fluctuations in certain commodity prices and transmission congestion costs. The fair value of those financial instruments that are determined to be derivatives are recorded as assets or liabilities on the Consolidated Balance Sheets. Derivative instruments representing unrealized gain positions are reported as derivative assets, and derivative instruments representing unrealized loss positions are reported as derivative liabilities at the end of each reporting period. Alliant Energy, IPL and WPL also have certain commodity purchase and sales contracts that have been designated, and qualify for, the normal purchase and sale exception and based on this designation, these contracts are accounted for on the accrual basis of accounting. Alliant Energy, IPL and WPL do not offset fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

Pension and Other Postretirement Benefit Plans

Pension and Other Postretirement Benefits Plans - Corporate Services sponsors various pension and other postretirement benefits plans. Some of the costs related to these plans are directly assigned to IPL and WPL for IPL’s and WPL’s non-bargaining employees who are participants in Corporate Services’ qualified and non-qualified defined benefit pension plans. The remaining costs related to Corporate Services’ plans are allocated to IPL, WPL, Resources and the parent company based on labor costs of plan participants.

Asset Impairments

Asset Impairments -

Property, Plant and Equipment of Regulated Operations - Property, plant and equipment of regulated operations are reviewed for possible impairment whenever events or changes in circumstances indicate all or a portion of the carrying value of the assets may be disallowed for rate-making purposes. If IPL or WPL are disallowed recovery of any portion of the carrying value of their regulated property, plant and equipment that has been recently completed or is probable of abandonment, an impairment charge is recognized equal to the amount of the carrying value that was disallowed. If IPL or WPL are disallowed a full or partial return on the carrying value of their regulated property, plant and equipment that has been recently completed or is probable of abandonment, an impairment charge is recognized equal to the difference between the carrying value and the present value of the future revenues expected from their regulated property, plant and equipment. Refer to Note 1(e) for discussion of impairments recorded by Alliant Energy and IPL in 2011 and 2010 related to IPL’s Whispering Willow - East wind project.

Property, Plant and Equipment of Non-regulated Operations and Intangible Assets - Property, plant and equipment of non-regulated operations and intangible assets are reviewed for possible impairment whenever events or changes in circumstances indicate the carrying value of the assets may not be recoverable. Impairment is indicated if the carrying value of an asset exceeds its undiscounted future cash flows. An impairment charge is recognized equal to the amount the carrying value exceeds the asset’s fair value. Refer to Note 1(e) for discussion of an impairment recorded by Alliant Energy and WPL in 2011 related to WPL’s Green Lake and Fond du Lac Counties wind site.

Unconsolidated Equity Investments - If events or circumstances indicate the carrying value of investments accounted for under the equity method of accounting may not be recoverable, potential impairment is assessed by comparing the fair value of these investments to their carrying values as well as assessing if a decline in fair value is temporary. If an impairment is indicated, a charge is recognized equal to the amount the carrying value exceeds the investment’s fair value.

Operating Leases

Operating Leases - Historically, WPL had certain PPAs that provided it exclusive rights to all or a substantial portion of the output from the specific generating facility over the contract term and that had pricing factors that required accounting for the PPAs as operating leases. Costs associated with these PPAs were included in “Electric production fuel and energy purchases” and “Purchased electric capacity” in Alliant Energy’s and WPL’s Consolidated Statements of Income based on monthly payments for these PPAs. Monthly capacity payments related to one of these PPAs was higher during the peak demand period from May 1 through September 30 and lower in all other periods during each calendar year. These seasonal differences in capacity charges were consistent with expected market pricing trends and the expected usage of energy from the facility.

Emission Allowances

Emission Allowances - Emission allowances are granted by the EPA at zero cost and permit the holder of the allowances to emit certain gaseous by-products of fossil fuel combustion, including SO2 and NOx. Unused emission allowances may be bought and sold or carried forward to be utilized in future years. Purchased emission allowances are recorded as intangible assets at their original cost and evaluated for impairment as long-lived assets to be held and used. Emission allowances allocated to or acquired by Alliant Energy, IPL or WPL are held primarily for consumption.

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
	2012	2011	2010	2012	2011	2010	2012	2011	2010
Amortization expense	$—	$13.4	$16.5	$—	$12.9	$13.1	$—	$0.5	$3.4

No amortization expense for emission allowances held at December 31, 2012 is currently expected to be recorded during 2013 through 2017.

Cash inflows and outflows related to sales and purchases of emission allowances are recorded as investing activities in the Consolidated Statements of Cash Flows.

AROs

AROs - The fair value of any retirement costs associated with an asset for which Alliant Energy, IPL and WPL have a legal obligation is recorded as a liability with an equivalent amount added to the asset cost when an asset is placed in service or when sufficient information becomes available to determine a reasonable estimate of the fair value of future retirement costs. The fair value of AROs is generally determined using discounted cash flow analyses. The liability is accreted to its present value each period and the capitalized cost is depreciated over the useful life of the related asset. Accretion and depreciation expenses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory assets on the Consolidated Balance Sheets. Upon regulatory approval to recover IPL’s AROs expenditures, its regulatory assets are amortized to depreciation and amortization expense in Alliant Energy’s and IPL’s Consolidated Statements of Income over the same time period that IPL’s customer rates are increased to recover the ARO expenditures. Effective January 1, 2013, WPL’s regulatory assets related to AROs are being recovered as a component of depreciation rates included in the most recent depreciation study approved by the PSCW in its May 2012 order. Accretion and depreciation expenses related to AROs for Alliant Energy’s non-regulated operations are recorded to depreciation and amortization expense in Alliant Energy’s Consolidated Statements of Income.

Upon settlement of the ARO liability, an entity settles the obligation for its recorded amount or incurs a gain or loss. Any gains or losses related to AROs for IPL’s and WPL’s regulated operations are recorded to regulatory liabilities or regulatory assets on the Consolidated Balance Sheets. Any gains or losses related to AROs for Alliant Energy’s non-regulated operations are recorded to non-regulated operating revenue or non-regulated operation and maintenance expense in Alliant Energy’s Consolidated Statements of Income.

Debt Issuance and Retirement Costs

Debt Issuance and Retirement Costs - Alliant Energy, IPL and WPL defer and amortize debt issuance costs and debt premiums or discounts over the expected lives of respective debt issues, considering maturity dates and, if applicable, redemption rights held by others. Alliant Energy’s non-regulated businesses and Corporate Services expense in the period of retirement any unamortized debt issuance costs and debt premiums or discounts on debt retired early.

Allowance for Doubtful Accounts

Allowance for Doubtful Accounts - Alliant Energy, IPL and WPL maintain allowances for doubtful accounts for estimated losses resulting from the inability of their customers to make required payments. Alliant Energy, IPL and WPL estimate the allowance for doubtful accounts based on historical write-offs, customer arrears and other economic factors within their service territories.

Variable Interest Entities (VIEs)

Variable Interest Entities (VIEs) - An entity is considered a VIE if its equity investors do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties or its equity investors lack any one of the following three characteristics: (1) power, through voting rights or similar rights, to direct the activities of the entity that most significantly impact the entity’s economic performance; (2) the obligation to absorb expected losses of the entity; or (3) the right to receive expected benefits of the entity. The primary beneficiary of a VIE is required to consolidate the VIE. If Alliant Energy, IPL or WPL have a variable interest in a VIE, a determination as to who the primary beneficiary is must be assessed.

Cash Flows Presentation

Cash Flows Presentation - Alliant Energy reports cash flows from continuing operations together with cash flows from discontinued operations in its Consolidated Statements of Cash Flows.

Comprehensive Income (Loss)

Comprehensive Income (Loss) - In 2012, 2011 and 2010, Alliant Energy’s other comprehensive income was $0, $0.6 million and $0, respectively; therefore, its comprehensive income was substantially equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was substantially equal to its net income attributable to Alliant Energy common shareowners for such periods. In 2012, 2011 and 2010, IPL and WPL had no other comprehensive income; therefore their comprehensive income was equal to their net income and their comprehensive income available for common stock was equal to their earnings available for common stock for such periods.

Regulated [Member]

Property, Plant and Equipment [Line Items]

Utility Property, Plant and Equipment

Utility Property, Plant and Equipment -

General - Utility plant in service (other than acquisition adjustments) is recorded at the original cost of acquisition or construction, which includes material, labor, contractor services, AFUDC and allocable overheads, such as supervision, engineering, benefits, certain taxes and transportation. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Ordinary retirements of utility plant in service and salvage value are netted and charged to accumulated depreciation upon removal from utility plant in service accounts and no gain or loss is recognized consistent with rate-making policies. Removal costs incurred reduce the regulatory liability.

Non-Regulated [Member]

Property, Plant and Equipment [Line Items]

Utility Property, Plant and Equipment

Non-regulated and Other Property, Plant and Equipment -

General - Non-regulated and other property, plant and equipment is recorded at the original cost of acquisition or construction, which includes material, labor and contractor services. Repairs, replacements and renewals of items of property determined to be less than a unit of property or that do not increase the property’s life or functionality are charged to maintenance expense. Upon retirement or sale of non-regulated and other property, plant and equipment, the original cost and related accumulated depreciation are removed from the accounts and any gain or loss is included in the Consolidated Statements of Income.

The Franklin County wind project and the Sheboygan Falls Energy Facility within Alliant Energy’s Non-regulated Generation business represent a large portion of the non-regulated and other property, plant and equipment. The Franklin County wind project was placed in service in the fourth quarter of 2012 and is being depreciated using the straight-line method over a 30-year period. As of December 31, 2012, Alliant Energy recorded $148 million (capitalized expenditures of $130 million, capitalized interest of $9 million, and AROs of $9 million) in “Non-regulated Generation property, plant and equipment” on its Consolidated Balance Sheet related to the wind project. Refer to Note 4(d) for discussion of a cash grant expected to be received related to the Franklin County wind project, which reduced the cost of the project. The Sheboygan Falls Energy Facility was placed into service in 2005 and is being depreciated using the straight-line method over a 35-year period. As of December 31, 2012, Alliant Energy recorded $111 million in “Non-regulated Generation property, plant and equipment” on its Consolidated Balance Sheet related to the Sheboygan Falls Energy Facility. The property, plant and equipment related to Corporate Services, Transportation and other non-regulated investments is recorded in “Alliant Energy Corporate Services, Inc. and other property, plant and equipment” on Alliant Energy’s Consolidated Balance Sheets and is depreciated using the straight-line method over periods ranging from 5 to 30 years.

IPL [Member]

Property, Plant and Equipment [Line Items]

General, Basis of Presentation

General, Basis of Accounting

General, Reclassification

General, Use of Estimates

Regulatory Assets and Regulatory Liabilities

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



	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Tax-related		$770.7		$634.7		$746.2		$614.6		$24.5		$20.1
Pension and other postretirement benefits costs	549.2		514.1		279.3		264.9		269.9		249.2
Asset retirement obligations (AROs)	62.4		65.9		38.6		48.7		23.8		17.2
Derivatives	40.2		77.7		16.3		33.5		23.9		44.2
Environmental-related costs	34.9		38.9		30.3		32.2		4.6		6.7
Emission allowances	30.0		30.0		30.0		30.0		—		—
Debt redemption costs	19.8		21.8		13.6		15.1		6.2		6.7
Proposed clean air compliance projects costs	16.7		14.9		7.8		6.9		8.9		8.0
IPL’s electric transmission service costs	16.6		24.9		16.6		24.9		—		—
Proposed coal-fired base-load projects costs	14.2		21.5		10.1		15.3		4.1		6.2
Other	57.7		50.6		29.1		31.2		28.6		19.4
		$1,612.4		$1,495.0		$1,217.9		$1,117.3		$394.5		$377.7

Proposed coal-fired base-load projects costs -

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



	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Cost of removal obligations		$408.7		$404.9		$268.0		$261.9		$140.7		$143.0
IPL’s tax benefit riders	355.8		349.6		355.8		349.6		—		—
Energy conservation cost recovery	55.1		29.6		10.0		4.7		45.1		24.9
IPL’s electric transmission assets sale	32.5		45.1		32.5		45.1		—		—
Commodity cost recovery	17.7		23.8		5.2		23.2		12.5		0.6
IPL’s DAEC sale	9.5		14.6		9.5		14.6		—		—
Other	36.8		42.5		20.4		22.2		16.4		20.3
		$916.1		$910.1		$701.4		$721.3		$214.7		$188.8

Refunds related to any remaining balance of IPL’s electric transmission assets sale regulatory liability are expected to be determined in future rate proceedings.

Refunds related to any remaining balance of IPL’s DAEC sale regulatory liability are expected to be determined in future rate proceedings.

Income Taxes

Cash and Cash Equivalents

Cash and Cash Equivalents - Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days.

Depreciation

AFUDC



	Alliant Energy						IPL						WPL
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Equity		$14.1		$7.6		$11.2		$5.2		$3.5		$3.0		$8.9		$4.1		$8.2
Debt	7.8		4.4		6.8		3.2		2.3		2.5		4.6		2.1		4.3
		$21.9		$12.0		$18.0		$8.4		$5.8		$5.5		$13.5		$6.2		$12.5



	2012	2011	2010
IPL (FERC formula)	8.2%	8.5%	4.8%
WPL (PSCW formula - retail jurisdiction) (a)	8.8%	8.8%	8.8%
WPL (FERC formula - wholesale jurisdiction)	7.9%	6.2%	7.2%

(a)

Operating Revenues

Operating Revenues -

Utility Cost Recovery Mechanisms

Utility Cost Recovery Mechanisms -

Financial Instruments

Pension and Other Postretirement Benefit Plans

Asset Impairments

Asset Impairments -

Emission Allowances



	Alliant Energy			IPL			WPL
	2012	2011	2010	2012	2011	2010	2012	2011	2010
Amortization expense	$—	$13.4	$16.5	$—	$12.9	$13.1	$—	$0.5	$3.4

No amortization expense for emission allowances held at December 31, 2012 is currently expected to be recorded during 2013 through 2017.

Cash inflows and outflows related to sales and purchases of emission allowances are recorded as investing activities in the Consolidated Statements of Cash Flows.

AROs

Debt Issuance and Retirement Costs

Allowance for Doubtful Accounts

Variable Interest Entities (VIEs)

Comprehensive Income (Loss)

IPL [Member] | Regulated [Member]

Property, Plant and Equipment [Line Items]

Utility Property, Plant and Equipment

Utility Property, Plant and Equipment -

IPL [Member] | Non-Regulated [Member]

Property, Plant and Equipment [Line Items]

Utility Property, Plant and Equipment

Non-regulated and Other Property, Plant and Equipment -

WPL [Member]

Property, Plant and Equipment [Line Items]

General, Basis of Presentation

General, Basis of Accounting

General, Reclassification

General, Use of Estimates

Regulatory Assets and Regulatory Liabilities

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



	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Tax-related		$770.7		$634.7		$746.2		$614.6		$24.5		$20.1
Pension and other postretirement benefits costs	549.2		514.1		279.3		264.9		269.9		249.2
Asset retirement obligations (AROs)	62.4		65.9		38.6		48.7		23.8		17.2
Derivatives	40.2		77.7		16.3		33.5		23.9		44.2
Environmental-related costs	34.9		38.9		30.3		32.2		4.6		6.7
Emission allowances	30.0		30.0		30.0		30.0		—		—
Debt redemption costs	19.8		21.8		13.6		15.1		6.2		6.7
Proposed clean air compliance projects costs	16.7		14.9		7.8		6.9		8.9		8.0
IPL’s electric transmission service costs	16.6		24.9		16.6		24.9		—		—
Proposed coal-fired base-load projects costs	14.2		21.5		10.1		15.3		4.1		6.2
Other	57.7		50.6		29.1		31.2		28.6		19.4
		$1,612.4		$1,495.0		$1,217.9		$1,117.3		$394.5		$377.7

Proposed coal-fired base-load projects costs -

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



	Alliant Energy				IPL				WPL
	2012		2011		2012		2011		2012		2011
Cost of removal obligations		$408.7		$404.9		$268.0		$261.9		$140.7		$143.0
IPL’s tax benefit riders	355.8		349.6		355.8		349.6		—		—
Energy conservation cost recovery	55.1		29.6		10.0		4.7		45.1		24.9
IPL’s electric transmission assets sale	32.5		45.1		32.5		45.1		—		—
Commodity cost recovery	17.7		23.8		5.2		23.2		12.5		0.6
IPL’s DAEC sale	9.5		14.6		9.5		14.6		—		—
Other	36.8		42.5		20.4		22.2		16.4		20.3
		$916.1		$910.1		$701.4		$721.3		$214.7		$188.8

Refunds related to any remaining balance of IPL’s electric transmission assets sale regulatory liability are expected to be determined in future rate proceedings.

Refunds related to any remaining balance of IPL’s DAEC sale regulatory liability are expected to be determined in future rate proceedings.

Income Taxes

Cash and Cash Equivalents

Cash and Cash Equivalents - Cash and cash equivalents include short-term liquid investments that have original maturities of less than 90 days.

Depreciation

AFUDC



	Alliant Energy						IPL						WPL
	2012		2011		2010		2012		2011		2010		2012		2011		2010
Equity		$14.1		$7.6		$11.2		$5.2		$3.5		$3.0		$8.9		$4.1		$8.2
Debt	7.8		4.4		6.8		3.2		2.3		2.5		4.6		2.1		4.3
		$21.9		$12.0		$18.0		$8.4		$5.8		$5.5		$13.5		$6.2		$12.5



	2012	2011	2010
IPL (FERC formula)	8.2%	8.5%	4.8%
WPL (PSCW formula - retail jurisdiction) (a)	8.8%	8.8%	8.8%
WPL (FERC formula - wholesale jurisdiction)	7.9%	6.2%	7.2%

(a)

Operating Revenues

Operating Revenues -

Utility Cost Recovery Mechanisms

Utility Cost Recovery Mechanisms -

Financial Instruments

Pension and Other Postretirement Benefit Plans

Asset Impairments

Asset Impairments -

Operating Leases

Emission Allowances



	Alliant Energy			IPL			WPL
	2012	2011	2010	2012	2011	2010	2012	2011	2010
Amortization expense	$—	$13.4	$16.5	$—	$12.9	$13.1	$—	$0.5	$3.4

No amortization expense for emission allowances held at December 31, 2012 is currently expected to be recorded during 2013 through 2017.

Cash inflows and outflows related to sales and purchases of emission allowances are recorded as investing activities in the Consolidated Statements of Cash Flows.

AROs

Debt Issuance and Retirement Costs

Allowance for Doubtful Accounts

Variable Interest Entities (VIEs)

Comprehensive Income (Loss)

WPL [Member] | Regulated [Member]

Property, Plant and Equipment [Line Items]

Utility Property, Plant and Equipment

Utility Property, Plant and Equipment -

WPL [Member] | Non-Regulated [Member]

Property, Plant and Equipment [Line Items]

Utility Property, Plant and Equipment

Non-regulated and Other Property, Plant and Equipment -