Item 1. CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

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Item 1. CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

For the Three Months
Ended March 31,
20242023
(in millions, except per share amounts)
Revenues:
Electric utility$791$768
Gas utility205276
Other utility1311
Non-utility2222
Total revenues1,0311,077
Operating expenses:
Electric production fuel and purchased power163157
Electric transmission service152146
Cost of gas sold114181
Other operation and maintenance160174
Depreciation and amortization189166
Taxes other than income taxes3131
Total operating expenses809855
Operating income222222
Other (income) and deductions:
Interest expense10794
Equity income from unconsolidated investments, net(15)(17)
Allowance for funds used during construction(19)(19)
Other13
Total other (income) and deductions7461
Income before income taxes148161
Income tax benefit(10)(2)
Net income attributable to Alliant Energy common shareowners$158$163
Weighted average number of common shares outstanding:
Basic256.2251.2
Diluted256.5251.4
Earnings per weighted average common share attributable to Alliant Energy common shareowners (basic and diluted)$0.62$0.65

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

March 31, 2024December 31, 2023
(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents$32$62
Accounts receivable, less allowance for expected credit losses426475
Production fuel, at weighted average cost6062
Gas stored underground, at weighted average cost5279
Materials and supplies, at weighted average cost208202
Regulatory assets218232
Other112160
Total current assets1,1081,272
Property, plant and equipment, net17,35417,157
Investments:
ATC Holdings392386
Other219216
Total investments611602
Other assets:
Regulatory assets2,0022,029
Deferred charges and other173177
Total other assets2,1752,206
Total assets$21,248$21,237
LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt$809$809
Commercial paper334475
Accounts payable438611
Regulatory liabilities100107
Other303302
Total current liabilities1,9842,304
Long-term debt, net (excluding current portion)8,5248,225
Other liabilities:
Deferred tax liabilities2,0382,042
Regulatory liabilities1,0361,023
Pension and other benefit obligations245249
Other604617
Total other liabilities3,9233,931
Commitments and contingencies (Note 13)
Equity:
Alliant Energy Corporation common equity:
Common stock - $0.01 par value - 480,000,000 shares authorized; 256,379,032 and 256,096,848 shares outstanding33
Additional paid-in capital3,0333,030
Retained earnings3,7913,756
Accumulated other comprehensive income21
Shares in deferred compensation trust - 341,937 and 379,006 shares at a weighted average cost of $34.96 and $34.48 per share(12)(13)
Total Alliant Energy Corporation common equity6,8176,777
Total liabilities and equity$21,248$21,237

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

For the Three Months
Ended March 31,
20242023
(in millions)
Cash flows from operating activities:
Net income$158$163
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization189166
Other(18)(6)
Other changes in assets and liabilities:
Accounts receivable(116)(86)
Gas stored underground2768
Derivative assets30115
Regulatory assets35(32)
Accounts payable12(97)
Regulatory liabilities(14)(95)
Other4(8)
Net cash flows from operating activities307188
Cash flows used for investing activities:
Construction and acquisition expenditures:
Utility business(478)(417)
Other(32)(34)
Cash receipts on sold receivables155173
Proceeds from sale of partial ownership interest in West Riverside—25
Other2(10)
Net cash flows used for investing activities(353)(263)
Cash flows from financing activities:
Common stock dividends(123)(113)
Proceeds from issuance of long-term debt597862
Payments to retire long-term debt(300)—
Net change in commercial paper and other short-term borrowings(141)(532)
Other(15)(5)
Net cash flows from financing activities18212
Net increase (decrease) in cash, cash equivalents and restricted cash(28)137
Cash, cash equivalents and restricted cash at beginning of period6324
Cash, cash equivalents and restricted cash at end of period$35$161
Supplemental cash flows information:
Cash paid during the period for:
Interest($97)($93)
Income taxes, net($2)$—
Significant non-cash investing and financing activities:
Accrued capital expenditures$204$254
Beneficial interest obtained in exchange for securitized accounts receivable$184$153

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

For the Three Months
Ended March 31,
20242023
(in millions)
Revenues:
Electric utility$392$388
Gas utility108150
Steam and other1311
Total revenues513549
Operating expenses:
Electric production fuel and purchased power6747
Electric transmission service103104
Cost of gas sold6095
Other operation and maintenance8695
Depreciation and amortization9696
Taxes other than income taxes1616
Total operating expenses428453
Operating income8596
Other (income) and deductions:
Interest expense4237
Allowance for funds used during construction(10)(3)
Other—1
Total other (income) and deductions3235
Income before income taxes5361
Income tax benefit(10)(11)
Net income$63$72

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of IPL’s common stock outstanding during the periods presented.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

March 31, 2024December 31, 2023
(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents$12$53
Accounts receivable, less allowance for expected credit losses204242
Production fuel, at weighted average cost2927
Gas stored underground, at weighted average cost1735
Materials and supplies, at weighted average cost126122
Regulatory assets8593
Other4251
Total current assets515623
Property, plant and equipment, net8,4508,298
Other assets:
Regulatory assets1,4821,484
Deferred charges and other8584
Total other assets1,5671,568
Total assets$10,532$10,489
LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt$500$500
Accounts payable213262
Accrued taxes6150
Accrued interest4940
Regulatory liabilities7972
Other97101
Total current liabilities9991,025
Long-term debt, net (excluding current portion)3,4453,445
Other liabilities:
Deferred tax liabilities1,0981,091
Regulatory liabilities569572
Pension and other benefit obligations4951
Other335331
Total other liabilities2,0512,045
Commitments and contingencies (Note 13)
Equity:
Interstate Power and Light Company common equity:
Common stock - $2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding3333
Additional paid-in capital2,9372,887
Retained earnings1,0671,054
Total Interstate Power and Light Company common equity4,0373,974
Total liabilities and equity$10,532$10,489

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

For the Three Months
Ended March 31,
20242023
(in millions)
Cash flows from operating activities:
Net income$63$72
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization9696
Other(11)1
Other changes in assets and liabilities:
Accounts receivable(119)(106)
Gas stored underground1834
Derivative assets2069
Accounts payable(7)(56)
Regulatory liabilities4(59)
Other12(27)
Net cash flows from operating activities7624
Cash flows from (used for) investing activities:
Construction and acquisition expenditures(253)(101)
Cash receipts on sold receivables155173
Other(9)(2)
Net cash flows from (used for) investing activities(107)70
Cash flows used for financing activities:
Common stock dividends(50)(70)
Capital contributions from parent50—
Other(10)(4)
Net cash flows used for financing activities(10)(74)
Net increase (decrease) in cash, cash equivalents and restricted cash(41)20
Cash, cash equivalents and restricted cash at beginning of period5315
Cash, cash equivalents and restricted cash at end of period$12$35
Supplemental cash flows information:
Cash paid during the period for:
Interest($32)($37)
Income taxes, net($2)$—
Significant non-cash investing and financing activities:
Accrued capital expenditures$110$98
Beneficial interest obtained in exchange for securitized accounts receivable$184$153

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

For the Three Months
Ended March 31,
20242023
(in millions)
Revenues:
Electric utility$399$380
Gas utility97126
Total revenues496506
Operating expenses:
Electric production fuel and purchased power96109
Electric transmission service4942
Cost of gas sold5386
Other operation and maintenance6366
Depreciation and amortization9068
Taxes other than income taxes1414
Total operating expenses365385
Operating income131121
Other (income) and deductions:
Interest expense4136
Allowance for funds used during construction(9)(16)
Other11
Total other (income) and deductions3321
Income before income taxes98100
Income tax expense612
Net income$92$88

Earnings per share data is not disclosed given Alliant Energy Corporation is the sole shareowner of all shares of WPL’s common stock outstanding during the periods presented.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)

March 31, 2024December 31, 2023
(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents$11$7
Accounts receivable, less allowance for expected credit losses209219
Production fuel, at weighted average cost3135
Gas stored underground, at weighted average cost3544
Materials and supplies, at weighted average cost7877
Regulatory assets133139
Prepaid gross receipts tax3849
Other1943
Total current assets554613
Property, plant and equipment, net8,4508,415
Other assets:
Regulatory assets520545
Deferred charges and other5761
Total other assets577606
Total assets$9,581$9,634
LIABILITIES AND EQUITY
Current liabilities:
Commercial paper$—$318
Accounts payable174293
Accrued interest4240
Regulatory liabilities2135
Other10589
Total current liabilities342775
Long-term debt, net3,3673,070
Other liabilities:
Deferred tax liabilities811827
Regulatory liabilities467451
Pension and other benefit obligations119121
Other480493
Total other liabilities1,8771,892
Commitments and contingencies (Note 13)
Equity:
Wisconsin Power and Light Company common equity:
Common stock - $5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding6666
Additional paid-in capital2,5332,478
Retained earnings1,3961,353
Total Wisconsin Power and Light Company common equity3,9953,897
Total liabilities and equity$9,581$9,634

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

For the Three Months
Ended March 31,
20242023
(in millions)
Cash flows from operating activities:
Net income$92$88
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization9068
Other(11)(12)
Other changes in assets and liabilities:
Gas stored underground935
Derivative assets1246
Regulatory assets29(37)
Accounts payable15(48)
Derivative liabilities(4)28
Regulatory liabilities(18)(35)
Other2752
Net cash flows from operating activities241185
Cash flows used for investing activities:
Construction and acquisition expenditures(225)(316)
Proceeds from sale of partial ownership interest in West Riverside—25
Other12(4)
Net cash flows used for investing activities(213)(295)
Cash flows from (used for) financing activities:
Common stock dividends(49)(46)
Capital contributions from parent55180
Proceeds from issuance of long-term debt297297
Net change in commercial paper(318)(230)
Other(9)(10)
Net cash flows from (used for) financing activities(24)191
Net increase in cash, cash equivalents and restricted cash481
Cash, cash equivalents and restricted cash at beginning of period75
Cash, cash equivalents and restricted cash at end of period$11$86
Supplemental cash flows information:
Cash paid during the period for:
Interest($40)($40)
Significant non-cash investing and financing activities:
Accrued capital expenditures$91$152

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.

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ALLIANT ENERGY CORPORATION

INTERSTATE POWER AND LIGHT COMPANY

WISCONSIN POWER AND LIGHT COMPANY

COMBINED NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the SEC. Accordingly, certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted, although management believes that the disclosures are adequate to make the information presented not misleading. These Financial Statements should be read in conjunction with the financial statements and the notes thereto included in the 2023 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 results of operations, financial position and cash flows have been made. Results for the three months ended March 31, 2024 are not necessarily indicative of results that may be expected for the year ending December 31, 2024.

A change in management’s estimates or assumptions could have a material impact on financial condition and results of operations during the period in which such change occurred. Certain prior period amounts in the Financial Statements and Notes have been reclassified to conform to the current period presentation for comparative purposes.

NOTE 2. REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

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

Alliant EnergyIPLWPL
March 31, 2024December 31, 2023March 31, 2024December 31, 2023March 31, 2024December 31, 2023
Tax-related$939$934$839$831$100$103
Pension and OPEB costs340347168171172176
Assets retired early2672732532591414
Asset retirement obligations (AROs)2001941651603534
Commodity cost recovery10012051295108
Derivatives9710233346468
WPL’s Western Wisconsin gas distribution expansion investments4444——4444
IPL’s Duane Arnold Energy Center PPA amendment36423642——
Other1972056868129137
$2,220$2,261$1,567$1,577$653$684

Derivatives - Refer to Note 10 for discussion of changes in Alliant Energy’s, IPL’s and WPL’s derivative liabilities/assets during the three months ended March 31, 2024, which resulted in comparable changes to regulatory assets/liabilities on the balance sheets.

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

Alliant EnergyIPLWPL
March 31, 2024December 31, 2023March 31, 2024December 31, 2023March 31, 2024December 31, 2023
Tax-related$563$566$297$299$266$267
Cost of removal obligations380366241242139124
Derivatives496528342131
Commodity cost recovery614825133635
Other838557562629
$1,136$1,130$648$644$488$486
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NOTE 3. PROPERTY, PLANT AND EQUIPMENT

WPL currently expects construction costs associated with its approximately 1,100 MW of new solar generation will exceed the construction cost estimates previously approved by the PSCW by approximately $180 million. In February 2024, the PSCW issued an order approving deferral of the incremental solar generation construction costs. The PSCW’s order did not authorize a deferral for the return on such costs. In March 2024, WPL filed for judicial review of the PSCW’s retail electric rate review order (2024/2025 forward-looking Test Period) and solar generation construction cost deferral order related to the recovery and deferral of the return on the incremental solar generation construction costs in 2024 and 2025. Alliant Energy and WPL concluded that there was not a probable disallowance of anticipated higher rate base amounts as of March 31, 2024 given construction costs were reasonably and prudently incurred.

NOTE 4. RECEIVABLES

Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. In March 2024, IPL amended and extended through March 2026 the purchase commitment from the third party to which it sells its receivables. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. As of March 31, 2024, IPL had $92 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three months ended March 31 were as follows (in millions):

20242023
Maximum outstanding aggregate cash proceeds$79$89
Average outstanding aggregate cash proceeds2458

The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions):

March 31, 2024December 31, 2023
Customer accounts receivable$125$130
Unbilled utility revenues8998
Other receivables11
Receivables sold to third party215229
Less: cash proceeds181
Deferred proceeds197228
Less: allowance for expected credit losses1312
Fair value of deferred proceeds$184$216

As of March 31, 2024, outstanding receivables past due under the Receivables Agreement were $22 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three months ended March 31 were as follows (in millions):

20242023
Collections$557$591
Write-offs, net of recoveries32

Effective April 2024, the limit on cash proceeds under the Receivables Agreement is $80 million.

NOTE 5. INVESTMENTS

Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three months ended March 31 was as follows (in millions):

20242023
ATC Holdings($12)($13)
Other(3)(4)
($15)($17)

NOTE 6. COMMON EQUITY

Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows:

Shares outstanding, January 1, 2024256,096,848
Shareowner Direct Plan127,917
Equity-based compensation plans154,267
Shares outstanding, March 31, 2024256,379,032
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Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):

Alliant EnergyAccumulatedShares in
AdditionalOtherDeferredTotal
CommonPaid-InRetainedComprehensiveCompensationCommon
StockCapitalEarningsIncome (Loss)TrustEquity
Three Months Ended March 31, 2024
Beginning balance, December 31, 2023$3$3,030$3,756$1($13)$6,777
Net income attributable to Alliant Energy common shareowners158158
Common stock dividends ($0.48 per share)(123)(123)
Shareowner Direct Plan issuances66
Equity-based compensation plans and other(3)1(2)
Other comprehensive income, net of tax11
Ending balance, March 31, 2024$3$3,033$3,791$2($12)$6,817
Three Months Ended March 31, 2023
Beginning balance, December 31, 2022$3$2,777$3,509$—($13)$6,276
Net income attributable to Alliant Energy common shareowners163163
Common stock dividends ($0.4525 per share)(113)(113)
Shareowner Direct Plan issuances66
Equity-based compensation plans and other(3)(3)
Other comprehensive loss, net of tax(1)(1)
Ending balance, March 31, 2023$3$2,780$3,559($1)($13)$6,328
IPLAdditionalTotal
CommonPaid-InRetainedCommon
StockCapitalEarningsEquity
Three Months Ended March 31, 2024
Beginning balance, December 31, 2023$33$2,887$1,054$3,974
Net income6363
Common stock dividends(50)(50)
Capital contributions from parent5050
Ending balance, March 31, 2024$33$2,937$1,067$4,037
Three Months Ended March 31, 2023
Beginning balance, December 31, 2022$33$2,807$968$3,808
Net income7272
Common stock dividends(70)(70)
Ending balance, March 31, 2023$33$2,807$970$3,810
WPLAdditionalTotal
CommonPaid-InRetainedCommon
StockCapitalEarningsEquity
Three Months Ended March 31, 2024
Beginning balance, December 31, 2023$66$2,478$1,353$3,897
Net income9292
Common stock dividends(49)(49)
Capital contributions from parent5555
Ending balance, March 31, 2024$66$2,533$1,396$3,995
Three Months Ended March 31, 2023
Beginning balance, December 31, 2022$66$2,233$1,192$3,491
Net income8888
Common stock dividends(46)(46)
Capital contributions from parent180180
Ending balance, March 31, 2023$66$2,413$1,234$3,713
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NOTE 7. DEBT

NOTE 7(a) Short-term Debt - In March 2024, Alliant Energy, IPL and WPL reallocated credit facility capacity amounts to $500 million for Alliant Energy at the parent company level, $200 million for IPL and $300 million for WPL, within the $1 billion total commitment. Information regarding commercial paper classified as short-term debt was as follows (dollars in millions):

March 31, 2024Alliant EnergyIPLWPL
Amount outstanding$334$—$—
Weighted average interest rates5.5%—%—%
Available credit facility capacity$666$200$300
Alliant EnergyIPLWPL
Three Months Ended March 31202420232024202320242023
Maximum amount outstanding (based on daily outstanding balances)$632$793$14$—$390$349
Average amount outstanding (based on daily outstanding balances)$487$574$1$—$255$304
Weighted average interest rates5.5%4.8%5.5%—%5.5%4.8%

NOTE 7(b) Long-term Debt - In March 2024, AEF entered into a $300 million variable rate (6% as of March 31, 2024) term loan credit agreement (with Alliant Energy as guarantor), which expires in March 2025. This term loan credit agreement amends and restates the term loan credit agreement that expired in March 2024, and retired the $300 million variable rate term loan set forth therein. AEF’s restated term loan credit agreement includes an option to increase the amount outstanding with one or more additional term loans in an aggregate amount not to exceed $100 million. In March 2024, WPL issued $300 million of 5.375% debentures due 2034. WPL’s debentures were issued as green bonds, and an amount equal to or in excess of the net proceeds will be allocated or disbursed for the development and acquisition of WPL’s solar EGUs.

Convertible Senior Notes - As of March 31, 2024, the conditions allowing holders of Alliant Energy’s convertible senior notes due 2026 (the Notes) to convert their Notes were not met, and as a result, the Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet. As of March 31, 2024, the net carrying amount of the Notes was $569 million, with unamortized debt issuance costs of $6 million, and the estimated fair value (Level 2) of the Notes was $567 million. As of March 31, 2024, there were no shares of Alliant Energy’s common stock related to the potential conversion of the Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the Notes.

NOTE 8. REVENUES

Disaggregation of revenues from contracts with customers, which correlates to revenues for each reportable segment, was as follows (in millions):

Alliant EnergyIPLWPL
Three Months Ended March 31202420232024202320242023
Electric Utility:
Retail - residential$297$285$150$143$147$142
Retail - commercial1861851141127273
Retail - industrial223216112107111109
Wholesale474613123434
Bulk power and other38363143522
Total Electric Utility791768392388399380
Gas Utility:
Retail - residential12616768935874
Retail - commercial618830443144
Retail - industrial573423
Transportation/other13147965
Total Gas Utility20527610815097126
Other Utility:
Steam12101210——
Other utility1111——
Total Other Utility13111311——
Non-Utility and Other:
Travero and other2222————
Total Non-Utility and Other2222————
Total revenues$1,031$1,077$513$549$496$506
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NOTE 9. INCOME TAXES

Income Tax Rates - Overall effective income tax rates for the three months ended March 31, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences.

Alliant EnergyIPLWPL
202420232024202320242023
Overall income tax rate(7%)(1%)(19%)(18%)6%12%

Deferred Tax Assets and Liabilities -

Carryforwards - At March 31, 2024, the carryforwards and expiration dates were estimated as follows (in millions):

Range of Expiration DatesAlliant EnergyIPLWPL
State net operating losses2025-2044$403$6$1
Federal tax credits2032-2044685462214

NOTE 10. BENEFIT PLANS

NOTE 10(a) Pension and OPEB Plans -

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three months ended March 31 are included below (in millions). For IPL and WPL, amounts are for their plan participants covered under plans they sponsor, as well as amounts directly assigned to them related to certain participants in the Alliant Energy and Corporate Services sponsored plans.

Defined Benefit Pension PlansOPEB Plans
Alliant Energy2024202320242023
Service cost$1$1$—$1
Interest cost111122
Expected return on plan assets(13)(13)(1)(1)
Amortization of actuarial loss67——
$5$6$1$2
Defined Benefit Pension PlansOPEB Plans
IPL2024202320242023
Service cost$1$1$—$—
Interest cost5511
Expected return on plan assets(7)(7)(1)(1)
Amortization of actuarial loss23——
$1$2$—$—
Defined Benefit Pension PlansOPEB Plans
WPL2024202320242023
Interest cost$5$5$1$1
Expected return on plan assets(6)(5)——
Amortization of actuarial loss33——
$2$3$1$1

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three months ended March 31 was as follows (in millions):

Alliant EnergyIPLWPL
202420232024202320242023
Compensation expense$4$3$2$2$2$1
Income tax benefits111———

As of March 31, 2024, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $22 million, $11 million and $10 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years.

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For the three months ended March 31, 2024, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.

Weighted Average
GrantsGrant Date Fair Value
Performance shares (total shareowner return metric)123,098$46.04
Performance shares (net income and diversity metrics) (formerly granted as performance restricted stock units)140,68348.40
Restricted stock units120,55748.40

As of March 31, 2024, 242,680 shares were included in the calculation of diluted EPS related to the nonvested equity awards.

NOTE 11. DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Notional Amounts - As of March 31, 2024, gross notional amounts and settlement/delivery years related to outstanding swap contracts, option contracts, physical forward contracts and FTRs that were accounted for as commodity derivative instruments were as follows (units in thousands):

ElectricityFTRsNatural Gas
MWhsYearsMWhsYearsDthsYears
Alliant Energy1,4122024-20264,1622024173,7462024-2032
IPL6732024-20261,444202478,7902024-2030
WPL7392024-20262,718202494,9562024-2032

Financial Statement Presentation - Derivative instruments are recorded at fair value each reporting date on the balance sheets as assets or liabilities as follows (in millions):

Alliant EnergyIPLWPL
March 31, 2024December 31, 2023March 31, 2024December 31, 2023March 31, 2024December 31, 2023
Current derivative assets$16$44$12$30$4$14
Non-current derivative assets404422241820
Current derivative liabilities495123222629
Non-current derivative liabilities4547783839

During the three months ended March 31, 2024, Alliant Energy’s, IPL’s and WPL’s derivative assets decreased primarily due to settlements of FTRs, natural gas and electricity contracts, and lower natural gas prices. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets resulted in comparable changes to regulatory assets/liabilities on the balance sheets.

Credit Risk-related Contingent Features - Various agreements contain credit risk-related contingent features, including requirements to maintain certain credit ratings and/or limitations on liability positions under the agreements based on credit ratings. Certain of these agreements with credit risk-related contingency features are accounted for as derivative instruments. In the event of a material change in creditworthiness or if liability positions exceed certain contractual limits, credit support may need to be provided up to the amount of exposure under the contracts, or the contracts may need to be unwound and underlying liability positions paid. At March 31, 2024 and December 31, 2023, the aggregate fair value of all derivative instruments with credit risk-related contingent features in a net liability position was not materially different than amounts that would be required to be posted as credit support to counterparties by Alliant Energy, IPL or WPL if the most restrictive credit risk-related contingent features for derivative agreements in a net liability position were triggered.

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Balance Sheet Offsetting - The fair value amounts of derivative instruments subject to a master netting arrangement are not netted by counterparty on the balance sheets. However, if the fair value amounts of derivative instruments by counterparty were netted, derivative assets and derivative liabilities related to commodity contracts would have been presented on the balance sheets as follows (in millions):

Alliant EnergyIPLWPL
GrossGrossGross
(as reported)Net(as reported)Net(as reported)Net
March 31, 2024
Derivative assets$56$26$34$17$22$9
Derivative liabilities946430136451
December 31, 2023
Derivative assets884754323415
Derivative liabilities98573086849

Fair value amounts recognized for the right to reclaim cash collateral (receivable) or the obligation to return cash collateral (payable) are not offset against fair value amounts recognized for derivative instruments executed with the same counterparty under the same master netting arrangement.

Interest Rate Derivative - The interest rate derivative associated with AEF’s interest rate swap maturing in January 2026 was valued based on quoted prices that utilize current market interest rate forecasts. As of March 31, 2024, $3 million of non-current interest rate derivative assets was recorded in “Deferred charges and other” on Alliant Energy’s balance sheet. This interest rate derivative was designated as a cash flow hedge, with changes in fair value recorded as other comprehensive income/loss. As of March 31, 2024, accumulated other comprehensive income included $2 million of income related to the interest rate swap. For the three months ended March 31, 2024 and 2023, $1 million and $1 million, respectively, of reductions to interest expense were recorded in Alliant Energy’s income statement related to the interest rate swap.

NOTE 12. FAIR VALUE MEASUREMENTS

Fair Value of Financial Instruments - The carrying amounts of current assets and current liabilities approximate fair value because of the short maturity of such financial instruments. Carrying amounts and related estimated fair values of other financial instruments were as follows (in millions):

Alliant EnergyMarch 31, 2024December 31, 2023
Fair ValueFair Value
CarryingLevelLevelLevelCarryingLevelLevelLevel
Amount123TotalAmount123Total
Assets:
Money market fund investments$10$10$—$—$10$45$45$—$—$45
Commodity derivatives56—46105688—592988
Interest rate derivatives3—3—31—1—1
Deferred proceeds184——184184216——216216
Liabilities:
Commodity derivatives94—9139498—93598
Long-term debt (incl. current maturities)9,333—9,051—9,0519,034—8,677—8,677
IPLMarch 31, 2024December 31, 2023
Fair ValueFair Value
CarryingLevelLevelLevelCarryingLevelLevelLevel
Amount123TotalAmount123Total
Assets:
Money market fund investments$6$6$—$—$6$45$45$—$—$45
Commodity derivatives34—2683454—302454
Deferred proceeds184——184184216——216216
Liabilities:
Commodity derivatives30—2733030—25530
Long-term debt (incl. current maturities)3,945—3,607—3,6073,945—3,664—3,664
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WPLMarch 31, 2024December 31, 2023
Fair ValueFair Value
CarryingLevelLevelLevelCarryingLevelLevelLevel
Amount123TotalAmount123Total
Assets:
Commodity derivatives$22$—$20$2$22$34$—$29$5$34
Liabilities:
Commodity derivatives64—64—6468—68—68
Long-term debt3,367—3,176—3,1763,070—2,933—2,933

Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions):

Alliant EnergyCommodity Contract Derivative
Assets and (Liabilities), netDeferred Proceeds
Three Months Ended March 312024202320242023
Beginning balance, January 1$24$19$216$185
Total net losses included in changes in net assets (realized/unrealized)(3)(4)——
Settlements (a)(14)(20)(32)(32)
Ending balance, March 31$7($5)$184$153
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at March 31($3)($4)$—$—
IPLCommodity Contract Derivative
Assets and (Liabilities), netDeferred Proceeds
Three Months Ended March 312024202320242023
Beginning balance, January 1$19$16$216$185
Total net gains (losses) included in changes in net assets (realized/unrealized)(4)1——
Settlements (a)(10)(17)(32)(32)
Ending balance, March 31$5$—$184$153
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31($4)$1$—$—
WPLCommodity Contract Derivative
Assets and (Liabilities), net
Three Months Ended March 3120242023
Beginning balance, January 1$5$3
Total net gains (losses) included in changes in net assets (realized/unrealized)1(5)
Settlements(4)(3)
Ending balance, March 31$2($5)
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at March 31$1($5)

(a)Settlements related to deferred proceeds are due to the change in the carrying amount of receivables sold less the allowance for expected credit losses associated with the receivables sold and cash amounts received from the receivables sold.

Commodity Contracts - The fair value of FTR and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets (liabilities) as follows (in millions):

Alliant EnergyIPLWPL
Excluding FTRsFTRsExcluding FTRsFTRsExcluding FTRsFTRs
March 31, 2024($1)$8($1)$6$—$2
December 31, 2023321316—5
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NOTE 13. COMMITMENTS AND CONTINGENCIES

NOTE 13(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including WPL’s expansion of battery storage, IPL’s and WPL’s expansion of solar generation, and IPL’s repowering of the existing Franklin County wind farm. At March 31, 2024, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $191 million, $80 million and $111 million, respectively.

NOTE 13(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At March 31, 2024, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):

Alliant EnergyIPLWPL
Natural gas$807$335$472
Coal16711057
Other (a)1245225
$1,098$497$554

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at March 31, 2024.

NOTE 13(c) Guarantees and Indemnifications -

Whiting Petroleum - Whiting Petroleum is an independent oil and gas company. In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, continues to guarantee the partnership obligations of an affiliate of Whiting Petroleum under multiple general partnership agreements in the oil and gas industry. The guarantees do not include a maximum limit. Based on information made available to Alliant Energy by Whiting Petroleum, the Whiting Petroleum affiliate holds an approximate 6% share in the partnerships, and currently known obligations include costs associated with the future abandonment of certain facilities owned by the partnerships. The general partnerships were formed under California law, and Alliant Energy Resources, LLC may need to perform under the guarantees if the affiliate of Whiting Petroleum is unable to meet its partnership obligations.

As of March 31, 2024, the currently known partnership obligations for the abandonment obligations are estimated at $49 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy estimates its expected loss to be a portion of the $49 million of known partnership abandonment obligations of the Whiting Petroleum affiliate and the other partners. Alliant Energy is not aware of any material liabilities related to these guarantees that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of March 31, 2024 and December 31, 2023.

Whiting Petroleum completed a business combination with Oasis Petroleum Inc. in 2022. The combined operations are now known as Chord Energy Corporation. The business combination is not expected to affect the scope of the Whiting Petroleum affiliate’s obligations to Alliant Energy or Alliant Energy’s related guarantees.

Non-utility Wind Farm in Oklahoma - In 2017, a wholly-owned subsidiary of AEF acquired a cash equity ownership interest in a non-utility wind farm located in Oklahoma. The wind farm provides electricity to a third party under a long-term PPA. Alliant Energy provided a parent guarantee of its subsidiary’s indemnification obligations under the related operating agreement and PPA. Alliant Energy’s obligations under the operating agreement were $51 million as of March 31, 2024 and will reduce annually until expiring in July 2047. Alliant Energy’s obligations under the PPA are subject to a maximum limit of $17 million and expire in December 2031, subject to potential extension. Alliant Energy is not aware of any material liabilities related to this guarantee that it is probable that it will be obligated to pay and therefore has not recognized any material liabilities related to this guarantee as of March 31, 2024 and December 31, 2023.

Transfers of Renewable Tax Credits - In 2023, IPL and WPL entered into agreements to transfer renewable tax credits from certain wind, solar and battery storage facilities to other corporate taxpayers in exchange for cash. IPL and WPL provided indemnifications associated with $76 million and $22 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers in 2023 in the event of an adverse interpretation of tax law, including whether the related tax credits meet the qualification requirements. Alliant Energy, IPL and WPL believe the likelihood of having to make any material cash payments under these indemnifications is remote.

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NOTE 13(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At March 31, 2024, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, which are not discounted, were as follows (in millions):

Alliant EnergyIPLWPL
Range of estimated future costs$8-$29$6-$18$2-$11
Current and non-current environmental liabilities$13$8$5

IPL Consent Decree - In 2015, the U.S. District Court for the Northern District of Iowa approved a Consent Decree that IPL entered into with the EPA, the Sierra Club, the State of Iowa and Linn County in Iowa, thereby resolving potential Clean Air Act issues associated with emissions from IPL’s coal-fired generating facilities in Iowa. IPL has completed various requirements under the Consent Decree. IPL’s remaining requirements include fuel switching or retiring Prairie Creek Units 1 and 3 by December 31, 2025. Alliant Energy and IPL currently expect to recover material costs incurred by IPL related to compliance with the terms of the Consent Decree from IPL’s electric customers.

Other Environmental Contingencies - In addition to the environmental liabilities discussed above, various environmental rules are monitored that may have a significant impact on future operations. Several of these environmental rules are subject to legal challenges, reconsideration and/or other uncertainties. Given uncertainties regarding the outcome, timing and compliance plans for these environmental matters, the complete financial impact of each of these rules is not able to be determined; however, future capital investments and/or modifications to EGUs and electric and gas distribution systems to comply with certain of these rules could be significant. Specific current, proposed or potential environmental matters include, among others: Cross-State Air Pollution Rule, Effluent Limitation Guidelines, Coal Combustion Residuals Rule, and various legislation and EPA regulations to monitor and regulate the emission of greenhouse gases, including the Clean Air Act.

NOTE 13(e) MISO Transmission Owner Return on Equity Complaints - A group of stakeholders, including MISO cooperative and municipal utilities, previously filed complaints with the Federal Energy Regulatory Commission (FERC) requesting a reduction to the base return on equity authorized for MISO transmission owners, including ITC Midwest LLC and ATC. In 2019, FERC issued an order on the previously filed complaints and reduced the base return on equity authorized for the MISO transmission owners to 9.88% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2020, FERC issued orders in response to various rehearing requests and increased the base return on equity authorized for the MISO transmission owners from 9.88% to 10.02% for November 12, 2013 through February 11, 2015, and subsequent to September 28, 2016. In 2022, the U.S. Court of Appeals for the District of Columbia vacated FERC’s prior orders that established the base return on equity authorized for the MISO transmission owners and remanded the cases to FERC for further proceedings, which may result in additional changes to the base return on equity authorized for the MISO transmission owners. Any further changes in FERC’s decisions may have an impact on Alliant Energy’s share of ATC’s future earnings and customer costs.

NOTE 13(f) Collective Bargaining Agreements - At March 31, 2024, employees covered by collective bargaining agreements represented 53%, 70% and 83% of total employees of Alliant Energy, IPL and WPL, respectively. In August 2024, IPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 204 (Cedar Rapids) expires, representing 18% and 53% of total employees of Alliant Energy and IPL, respectively.

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NOTE 14. SEGMENTS OF BUSINESS

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s business segments is as follows. Intersegment revenues were not material to their respective operations.

Alliant EnergyATC Holdings,Alliant
UtilityNon-Utility,Energy
ElectricGasOtherTotalParent and OtherConsolidated
(in millions)
Three Months Ended March 31, 2024
Revenues$791$205$13$1,009$22$1,031
Operating income1644752166222
Net income attributable to Alliant Energy common shareowners1553158
Three Months Ended March 31, 2023
Revenues$768$276$11$1,055$22$1,077
Operating income1635042175222
Net income attributable to Alliant Energy common shareowners1603163
IPLElectricGasOtherTotal
(in millions)
Three Months Ended March 31, 2024
Revenues$392$108$13$513
Operating income5722685
Net income63
Three Months Ended March 31, 2023
Revenues$388$150$11$549
Operating income6627396
Net income72
WPLElectricGasOtherTotal
(in millions)
Three Months Ended March 31, 2024
Revenues$399$97$—$496
Operating income (loss)10725(1)131
Net income92
Three Months Ended March 31, 2023
Revenues$380$126$—$506
Operating income97231121
Net income88

NOTE 15. RELATED PARTIES

Service Agreements - Pursuant to service agreements, IPL and WPL receive various administrative and general services from an affiliate, Corporate Services. These services are billed to IPL and WPL at cost based on expenses incurred by Corporate Services for the benefit of IPL and WPL, respectively. These costs consisted primarily of employee compensation and benefits, fees associated with various professional services, depreciation and amortization of property, plant and equipment, and a return on net assets. Corporate Services also acts as agent on behalf of IPL and WPL pursuant to the service agreements. As agent, Corporate Services enters into energy, capacity, ancillary services, and transmission sale and purchase transactions within MISO. Corporate Services assigns such sales and purchases among IPL and WPL based on statements received from MISO. The amounts billed for services provided, sales credited and purchases for the three months ended March 31 were as follows (in millions):

IPLWPL
2024202320242023
Corporate Services billings$43$40$40$36
Sales credited—72213
Purchases billed9693715
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Net intercompany payables to Corporate Services were as follows (in millions):

IPLWPL
March 31, 2024December 31, 2023March 31, 2024December 31, 2023
Net payables to Corporate Services$132$129$70$72

ATC - Pursuant to various agreements, WPL receives a range of transmission services from ATC. WPL provides operation, maintenance, and construction services to ATC. WPL and ATC also bill each other for use of shared facilities owned by each party. The related amounts billed between the parties for the three months ended March 31 were as follows (in millions):

20242023
ATC billings to WPL$37$34
WPL billings to ATC36

WPL owed ATC net amounts of $10 million as of March 31, 2024 and $10 million as of December 31, 2023.

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