Summary Of Significant Accounting Policies

3 Months Ended

Mar. 31, 2013

Summary Of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

(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 months ended March 31, 2013 and 2012, the condensed consolidated financial position at March 31, 2013 and December 31, 2012, and the condensed consolidated statements of cash flows for the three months ended March 31, 2013 and 2012 have been made. Results for the three months ended March 31, 2013 are not necessarily indicative of results that may be expected for the year ending December 31, 2013. 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 in the Condensed Consolidated Financial Statements and Combined Notes to Condensed 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.

(b) Regulatory Assets and Regulatory Liabilities -

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

	Alliant Energy				IPL				WPL
	March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012
Tax-related		$781.9		$770.7		$757.2		$746.2		$24.7		$24.5
Pension and other postretirement benefits costs	541.4		549.2		275.6		279.3		265.8		269.9
Asset retirement obligations (AROs)	62.9		62.4		38.5		38.6		24.4		23.8
Environmental-related costs	32.2		34.9		27.7		30.3		4.5		4.6
Emission allowances	30.0		30.0		30.0		30.0		—		—
Derivatives	17.0		40.2		6.3		16.3		10.7		23.9
Other	117.2		125.0		72.6		77.2		44.6		47.8
		$1,582.6		$1,612.4		$1,207.9		$1,217.9		$374.7		$394.5

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

	Alliant Energy				IPL				WPL
	March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012
Cost of removal obligations		$411.3		$408.7		$270.6		$268.0		$140.7		$140.7
IPL’s tax benefit riders	335.1		355.8		335.1		355.8		—		—
Energy conservation cost recovery	61.3		55.1		16.4		10.0		44.9		45.1
IPL’s electric transmission assets sale	29.7		32.5		29.7		32.5		—		—
Commodity cost recovery	39.2		17.7		25.4		5.2		13.8		12.5
Other	59.1		46.3		38.0		29.9		21.1		16.4
		$935.7		$916.1		$715.2		$701.4		$220.5		$214.7

Tax-related - Alliant Energy’s and IPL’s tax-related regulatory assets are generally impacted by certain property-related differences at IPL for which deferred tax is not recorded in the income statement pursuant to Iowa rate-making principles. Deferred tax amounts are recorded to regulatory assets, along with the necessary revenue requirement tax gross-ups. During the three months ended March 31, 2013, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due toqualifying repair expenditures at IPL.

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 Condensed Consolidated Balance Sheets for the three months ended March 31, 2013. Refer to Note 11 for additional details of derivative assets and derivative liabilities.

IPL’s tax benefit riders - Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities in the above table decreased $20.7 million during the three months ended March 31, 2013 due to the following items:

Electric tax benefit rider - In January 2011, the Iowa Utilities Board (IUB) approved an electric tax benefit rider proposed by IPL, which utilizes regulatory liabilities to credit bills of Iowa retail electric customers beginning in February 2011 to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs and allocation of insurance proceeds from floods in 2008. IPL utilized $18.3 million of regulatory liabilities to credit Iowa retail electric customers’ bills during the three months ended March 31, 2013.

Gas tax benefit rider - In November 2012, the IUB approved a gas tax benefit rider proposed by IPL, which utilizes regulatory liabilities to credit bills of Iowa retail gas customers beginning in January 2013 to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs and allocation of insurance proceeds from floods in 2008. IPL utilized $2.4 million of regulatory liabilities to credit Iowa retail gas customers’ bills during the three months ended March 31, 2013.

Refer to Note 4 for additional details regarding IPL’s tax benefit riders.

(c) Comprehensive Income - For the three months ended March 31, 2013 and 2012, Alliant Energy had no other comprehensive income; therefore, its comprehensive income was equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three months ended March 31, 2013 and 2012, 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.

IPL [Member]

Summary Of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

(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 months ended March 31, 2013 and 2012, the condensed consolidated financial position at March 31, 2013 and December 31, 2012, and the condensed consolidated statements of cash flows for the three months ended March 31, 2013 and 2012 have been made. Results for the three months ended March 31, 2013 are not necessarily indicative of results that may be expected for the year ending December 31, 2013. 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 in the Condensed Consolidated Financial Statements and Combined Notes to Condensed 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.

(b) Regulatory Assets and Regulatory Liabilities -

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

	Alliant Energy				IPL				WPL
	March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012
Tax-related		$781.9		$770.7		$757.2		$746.2		$24.7		$24.5
Pension and other postretirement benefits costs	541.4		549.2		275.6		279.3		265.8		269.9
Asset retirement obligations (AROs)	62.9		62.4		38.5		38.6		24.4		23.8
Environmental-related costs	32.2		34.9		27.7		30.3		4.5		4.6
Emission allowances	30.0		30.0		30.0		30.0		—		—
Derivatives	17.0		40.2		6.3		16.3		10.7		23.9
Other	117.2		125.0		72.6		77.2		44.6		47.8
		$1,582.6		$1,612.4		$1,207.9		$1,217.9		$374.7		$394.5

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

	Alliant Energy				IPL				WPL
	March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012
Cost of removal obligations		$411.3		$408.7		$270.6		$268.0		$140.7		$140.7
IPL’s tax benefit riders	335.1		355.8		335.1		355.8		—		—
Energy conservation cost recovery	61.3		55.1		16.4		10.0		44.9		45.1
IPL’s electric transmission assets sale	29.7		32.5		29.7		32.5		—		—
Commodity cost recovery	39.2		17.7		25.4		5.2		13.8		12.5
Other	59.1		46.3		38.0		29.9		21.1		16.4
		$935.7		$916.1		$715.2		$701.4		$220.5		$214.7

Tax-related - Alliant Energy’s and IPL’s tax-related regulatory assets are generally impacted by certain property-related differences at IPL for which deferred tax is not recorded in the income statement pursuant to Iowa rate-making principles. Deferred tax amounts are recorded to regulatory assets, along with the necessary revenue requirement tax gross-ups. During the three months ended March 31, 2013, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due toqualifying repair expenditures at IPL.

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 Condensed Consolidated Balance Sheets for the three months ended March 31, 2013. Refer to Note 11 for additional details of derivative assets and derivative liabilities.

IPL’s tax benefit riders - Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities in the above table decreased $20.7 million during the three months ended March 31, 2013 due to the following items:

Electric tax benefit rider - In January 2011, the Iowa Utilities Board (IUB) approved an electric tax benefit rider proposed by IPL, which utilizes regulatory liabilities to credit bills of Iowa retail electric customers beginning in February 2011 to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs and allocation of insurance proceeds from floods in 2008. IPL utilized $18.3 million of regulatory liabilities to credit Iowa retail electric customers’ bills during the three months ended March 31, 2013.

Gas tax benefit rider - In November 2012, the IUB approved a gas tax benefit rider proposed by IPL, which utilizes regulatory liabilities to credit bills of Iowa retail gas customers beginning in January 2013 to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs and allocation of insurance proceeds from floods in 2008. IPL utilized $2.4 million of regulatory liabilities to credit Iowa retail gas customers’ bills during the three months ended March 31, 2013.

Refer to Note 4 for additional details regarding IPL’s tax benefit riders.

(c) Comprehensive Income - For the three months ended March 31, 2013 and 2012, Alliant Energy had no other comprehensive income; therefore, its comprehensive income was equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three months ended March 31, 2013 and 2012, 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.

WPL [Member]

Summary Of Significant Accounting Policies

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

(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 months ended March 31, 2013 and 2012, the condensed consolidated financial position at March 31, 2013 and December 31, 2012, and the condensed consolidated statements of cash flows for the three months ended March 31, 2013 and 2012 have been made. Results for the three months ended March 31, 2013 are not necessarily indicative of results that may be expected for the year ending December 31, 2013. 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 in the Condensed Consolidated Financial Statements and Combined Notes to Condensed 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.

(b) Regulatory Assets and Regulatory Liabilities -

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

	Alliant Energy				IPL				WPL
	March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012
Tax-related		$781.9		$770.7		$757.2		$746.2		$24.7		$24.5
Pension and other postretirement benefits costs	541.4		549.2		275.6		279.3		265.8		269.9
Asset retirement obligations (AROs)	62.9		62.4		38.5		38.6		24.4		23.8
Environmental-related costs	32.2		34.9		27.7		30.3		4.5		4.6
Emission allowances	30.0		30.0		30.0		30.0		—		—
Derivatives	17.0		40.2		6.3		16.3		10.7		23.9
Other	117.2		125.0		72.6		77.2		44.6		47.8
		$1,582.6		$1,612.4		$1,207.9		$1,217.9		$374.7		$394.5

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

	Alliant Energy				IPL				WPL
	March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012		March 31, 2013		December 31, 2012
Cost of removal obligations		$411.3		$408.7		$270.6		$268.0		$140.7		$140.7
IPL’s tax benefit riders	335.1		355.8		335.1		355.8		—		—
Energy conservation cost recovery	61.3		55.1		16.4		10.0		44.9		45.1
IPL’s electric transmission assets sale	29.7		32.5		29.7		32.5		—		—
Commodity cost recovery	39.2		17.7		25.4		5.2		13.8		12.5
Other	59.1		46.3		38.0		29.9		21.1		16.4
		$935.7		$916.1		$715.2		$701.4		$220.5		$214.7

Tax-related - Alliant Energy’s and IPL’s tax-related regulatory assets are generally impacted by certain property-related differences at IPL for which deferred tax is not recorded in the income statement pursuant to Iowa rate-making principles. Deferred tax amounts are recorded to regulatory assets, along with the necessary revenue requirement tax gross-ups. During the three months ended March 31, 2013, Alliant Energy’s and IPL’s tax-related regulatory assets increased primarily due toqualifying repair expenditures at IPL.

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 Condensed Consolidated Balance Sheets for the three months ended March 31, 2013. Refer to Note 11 for additional details of derivative assets and derivative liabilities.

IPL’s tax benefit riders - Alliant Energy’s and IPL’s “IPL’s tax benefit riders” regulatory liabilities in the above table decreased $20.7 million during the three months ended March 31, 2013 due to the following items:

Electric tax benefit rider - In January 2011, the Iowa Utilities Board (IUB) approved an electric tax benefit rider proposed by IPL, which utilizes regulatory liabilities to credit bills of Iowa retail electric customers beginning in February 2011 to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs and allocation of insurance proceeds from floods in 2008. IPL utilized $18.3 million of regulatory liabilities to credit Iowa retail electric customers’ bills during the three months ended March 31, 2013.

Gas tax benefit rider - In November 2012, the IUB approved a gas tax benefit rider proposed by IPL, which utilizes regulatory liabilities to credit bills of Iowa retail gas customers beginning in January 2013 to help offset the impact of rate increases on such customers. These regulatory liabilities are related to tax benefits from tax accounting method changes for repairs expenditures, allocation of mixed service costs and allocation of insurance proceeds from floods in 2008. IPL utilized $2.4 million of regulatory liabilities to credit Iowa retail gas customers’ bills during the three months ended March 31, 2013.

Refer to Note 4 for additional details regarding IPL’s tax benefit riders.

(c) Comprehensive Income - For the three months ended March 31, 2013 and 2012, Alliant Energy had no other comprehensive income; therefore, its comprehensive income was equal to its net income and its comprehensive income attributable to Alliant Energy common shareowners was equal to its net income attributable to Alliant Energy common shareowners for such periods. For the three months ended March 31, 2013 and 2012, 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.