ALLIANT ENERGY CORP 10-Q

lnt-20240331 Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-Q ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 or ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Name of Registrant, State of Incorporation, Address of Principal Executive Offices, Telephone Number, Commission File Number, IRS Employer Identification Number ALLIANT ENERGY CORP ORATION (a Wisconsin Corporation) 4902 N. Biltmore Lane Madison , Wisconsin 53718 Telephone ( 608 ) 458-3311 Commission File Number - 1-9894 IRS Employer Identification Number - 39-1380265 INTERSTATE POWER & LIGHT CO MPANY (an Iowa corporation) Alliant Energy Tower Cedar Rapids , Iowa 52401 Telephone ( 319 ) 786-4411 Commission File Number - 1-4117 IRS Employer Identification Number - 42-0331370 WISCONSIN POWER & LIGHT CO MPANY (a Wisconsin corporation) 4902 N. Biltmore Lane Madison , Wisconsin 53718 Telephone ( 608 ) 458-3311 Commission File Number - 0-337 IRS Employer Identification Number - 39-0714890 This combined Form 10-Q is separately filed by Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company. Information contained in the Form 10-Q relating to Interstate Power and Light Company and Wisconsin Power and Light Company is filed by each such registrant on its own behalf. Each of Interstate Power and Light Company and Wisconsin Power and Light Company makes no representation as to information relating to registrants other than itself. Securities registered pursuant to Section 12(b) of the Act: Alliant Energy Corporation, Common Stock, $0.01 Par Value , Trading Symbol LNT , Nasdaq Global Select Market Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Alliant Energy Corporation - Yes ☒ No ☐ Interstate Power and Light Company - Yes ☒ No ☐ Wisconsin Power and Light Company - Yes ☒ No ☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Alliant Energy Corporation - Yes ☒ No ☐ Interstate Power and Light Company - Yes ☒ No ☐ Wisconsin Power and Light Company - Yes ☒ No ☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act. Alliant Energy Corporation - Large Accelerated Filer ☒ Accelerated Filer ☐ Non-accelerated Filer ☐ Smaller Reporting Company ☐ Emerging Growth Company ☐ Interstate Power and Light Company - Large Accelerated Filer ☐ Accelerated Filer ☐ Non-accelerated Filer ☒ Smaller Reporting Company ☐ Emerging Growth Company ☐ Wisconsin Power and Light Company - Large Accelerated Filer ☐ Accelerated Filer ☐ Non-accelerated Filer ☒ Smaller Reporting Company ☐ Emerging Growth Company ☐ If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. Alliant Energy Corporation ☐ Interstate Power and Light Company ☐ Wisconsin Power and Light Company ☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Alliant Energy Corporation - Yes ☐ No ☒ Interstate Power and Light Company - Yes ☐ No ☒ Wisconsin Power and Light Company - Yes ☐ No ☒ Number of shares outstanding of each class of common stock as of March 31, 2024: Alliant Energy Corporation, Common Stock, $0.01 par value, 256,379,032 shares outstanding Interstate Power and Light Company, Common Stock, $2.50 par value, 13,370,788 shares outstanding (all outstanding shares are owned beneficially and of record by Alliant Energy Corporation) Wisconsin Power and Light Company, Common Stock, $5 par value, 13,236,601 shares outstanding (all outstanding shares are owned beneficially and of record by Alliant Energy Corporation) Table of Contents TABLE OF CONTENTS Page Definitions 1 Forward-looking Statements 1 Part I. Financial Information 3 Item 1. Condensed Consolidated Financial Statements (Unaudited) 3 Alliant Energy Corporation 3 Interstate Power and Light Company 6 Wisconsin Power and Light Company 9 Combined Notes to Condensed Consolidated Financial Statements 12 1. Summary of Significant Accounting Policies 12 2. Regulatory Matters 12 3. Property, Plant and Equipment 13 4 . Receivables 13 5 . Investments 13 6 . Common Equity 13 7 . Debt 15 8 . Revenues 15 9 . Income Taxes 16 10 . Benefit Plans 16 1 1 . Derivative Instruments 17 1 2 . Fair Value Measurements 18 1 3 . Commitments and Contingencies 20 1 4 . Segments of Business 22 1 5 . Related Parties 22 Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations 23 Item 3. Quantitative and Qualitative Disclosures About Market Risk 29 Item 4. Controls and Procedures 29 Part II. Other Information 29 Item 1. Legal Proceedings 29 Item 1A. Risk Factors 29 Item 2. Unregistered Sales of Equity Securities and Use of Proceeds 29 Item 5. Other Information 30 Item 6. Exhibits 30 Signatures 30 Table of Contents DEFINITIONS The following abbreviations or acronyms used in this report are defined below: Abbreviation or Acronym Definition Abbreviation or Acronym Definition 2023 Form 10-K Combined Annual Report on Form 10-K filed by Alliant Energy, IPL and WPL for the year ended Dec. 31, 2023 IUB Iowa Utilities Board AEF Alliant Energy Finance, LLC MDA Management’s Discussion and Analysis of Financial Condition and Results of Operations AFUDC Allowance for funds used during construction MISO Midcontinent Independent System Operator, Inc. Alliant Energy Alliant Energy Corporation MW Megawatt ATC American Transmission Company LLC MWh Megawatt-hour ATC Holdings Interest in American Transmission Company LLC and ATC Holdco LLC N/A Not applicable Corporate Services Alliant Energy Corporate Services, Inc. Note(s) Combined Notes to Condensed Consolidated Financial Statements Dth Dekatherm OPEB Other postretirement benefits EGU Electric generating unit PPA Purchased power agreement EPA U.S. Environmental Protection Agency PSCW Public Service Commission of Wisconsin EPS Earnings per weighted average common share SEC Securities and Exchange Commission Financial Statements Condensed Consolidated Financial Statements U.S. United States of America FTR Financial transmission right West Riverside West Riverside Energy Center and Solar Facility GAAP U.S. generally accepted accounting principles Whiting Petroleum Whiting Petroleum Corporation IPL Interstate Power and Light Company WPL Wisconsin Power and Light Company FORWARD-LOOKING STATEMENTS Statements contained in this report that are not of historical fact are forward-looking statements intended to qualify for the safe harbors from liability established by the Private Securities Litigation Reform Act of 1995. These forward-looking statements can be identified as such because the statements include words such as “may,” “believe,” “expect,” “anticipate,” “plan,” “project,” “will,” “projections,” “estimate,” or other words of similar import. Similarly, statements that describe future financial performance or plans or strategies are forward-looking statements. Such forward-looking statements are subject to certain risks and uncertainties that could cause actual results to differ materially from those expressed in, or implied by, such statements. Some, but not all, of the risks and uncertainties of Alliant Energy, IPL and WPL that could materially affect actual results include: • the direct or indirect effects resulting from cybersecurity incidents or attacks on Alliant Energy, IPL, WPL, or their suppliers, contractors and partners, or responses to such incidents; • the impact of customer- and third party-owned generation, including alternative electric suppliers, in IPL’s and WPL’s service territories on system reliability, operating expenses and customers’ demand for electricity; • economic conditions and the impact of business or facility closures in IPL’s and WPL’s service territories; • the impact of energy efficiency, franchise retention and customer disconnects on sales volumes and operating income; • the impact that price changes may have on IPL’s and WPL’s customers’ demand for electric, gas and steam services and their ability to pay their bills; • changes in the price of delivered natural gas, transmission, purchased electricity and delivered coal, particularly during elevated market prices, and any resulting changes to counterparty credit risk, due to shifts in supply and demand caused by market conditions, regulations and MISO’s seasonal resource adequacy process; • IPL’s and WPL’s ability to obtain adequate and timely rate relief to allow for, among other things, the recovery of and/or the return on costs, including fuel costs, operating costs, transmission costs, capacity costs, deferred expenditures, deferred tax assets, tax expense, interest expense, capital expenditures, and remaining costs related to EGUs that may be permanently closed and certain other retired assets, decreases in sales volumes, earning their authorized rates of return, payments to their parent of expected levels of dividends, and the impact of rate design on current and potential customers’ demand for energy in their service territories; • weather effects on utility sales volumes and operations; • the ability to obtain deferral treatment for the recovery of and a return on prudently incurred costs in between rate reviews; • the ability to obtain regulatory approval for construction projects with acceptable conditions; • the ability to complete construction of renewable generation and storage projects by planned in-service dates and within the cost targets set by regulators due to cost increases of and access to materials, equipment and commodities, which could result from tariffs, duties or other assessments, such as any additional tariffs resulting from U.S. Department of Commerce investigations into and any decisions made regarding the sourcing of solar project materials and equipment from certain countries, labor issues or supply shortages, the ability to successfully resolve warranty issues or contract disputes, the ability to achieve the expected level of tax benefits based on tax guidelines, project costs and the level of electricity output generated by qualifying generating facilities, and the ability to efficiently utilize the renewable generation and storage project tax benefits for the benefit of customers; • WPL’s ability to obtain rate relief to allow for the return on costs of solar generation projects that exceed initial cost estimates; • the impacts of changes in the tax code, including tax rates, minimum tax rates, adjustments made to deferred tax assets and liabilities, and changes impacting the availability of and ability to transfer renewable tax credits; • the ability to utilize tax credits generated to date, and those that may be generated in the future, before they expire, as well as the ability to transfer tax credits that may be generated in the future at adequate pricing; • disruptions to ongoing operations and the supply of materials, services, equipment and commodities needed to construct solar generation, battery storage and electric and gas distribution projects, which may result from geopolitical issues, supplier manufacturing constraints, regulatory requirements, labor issues or transportation issues, and thus affect the ability to meet capacity requirements and result in increased capacity expense; • inflation and higher interest rates; 1 Table of Contents • the future development of technologies related to electrification, and the ability to reliably store and manage electricity; • federal and state regulatory or governmental actions, including the impact of legislation, and regulatory agency orders and changes in public policy; • employee workforce factors, including the ability to hire and retain employees with specialized skills, impacts from employee retirements, changes in key executives, ability to create desired corporate culture, collective bargaining agreements and negotiations, work stoppages or restructurings; • disruptions in the supply and delivery of natural gas, purchased electricity and coal; • changes to the creditworthiness of, or performance of obligations by, counterparties with which Alliant Energy, IPL and WPL have contractual arrangements, including participants in the energy markets and fuel suppliers and transporters; • the impact of penalties or third-party claims related to, or in connection with, a failure to maintain the security of personally identifiable information, including associated costs to notify affected persons and to mitigate their information security concerns; • impacts that terrorist attacks may have on Alliant Energy’s, IPL’s and WPL’s operations and recovery of costs associated with restoration activities, or on the operations of Alliant Energy’s investments; • any material post-closing paym ents related to any past asset divestitures, including the transfer of renewable tax credits and the sale of Whiting Petroleum, which could result from, among other things, indemnification agreements, warranties, guarantees or litigation; • continued access to the capital markets on competitive terms and rates, and the actions of credit rating agencies; • changes to MISO’s resource adequacy process establishing capacity planning reserve margin and capacity accreditation requirements that may impact how and when new and existing generating facilities, including IPL’s and WPL’s additional solar generation, may be accredited with energy capacity, and may require IPL and WPL to adjust their current resource plans, to add resources to meet the requirements of MISO’s process, or procure capacity in the market whereby such costs might not be recovered in rates; • issues associated with environmental remediation and environmental compliance, including compliance with all environmental and emissions permits and future changes in environmental laws and regulations, including the Coal Combustion Residuals Rule, Cross-State Air Pollution Rule and federal, state or local regulations for greenhouse gases emissions reductions from new and existing fossil-fueled EGUs under the Clean Air Act, and litigation associated with environmental requirements; • increased pressure from customers, investors and other stakeholders to more rapidly reduce greenhouse gases emissions; • the ability to defend against environmental claims brought by state and federal agencies, such as the EPA and state natural resources agencies, or third parties, such as the Sierra Club, and the impact on operating expenses of defending and resolving such claims; • the direct or indirect effects resulting from breakdown or failure of equipment in the operation of electric and gas distribution systems, such as mechanical problems and explosions or fires, and compliance with electric and gas transmission and distribution safety regulations, including regulations promulgated by the Pipeline and Hazardous Materials Safety Administration; • issues related to the availability and operations of EGUs, including start-up risks, breakdown or failure of equipment, availability of warranty coverage and successful resolution of warranty issues or contract disputes for equipment breakdowns or failures, performance below expected or contracted levels of output or efficiency, operator error, employee safety, transmission constraints, compliance with mandatory reliability standards and risks related to recovery of resulting incremental operating, fuel-related and capital costs through rates; • impacts that excessive heat, excessive cold, storms, wildfires, or natural disasters may have on Alliant Energy’s, IPL’s and WPL’s operations and construction activities, and recovery of costs associated with restoration activities, or on the operations of Alliant Energy’s investments; • Alliant Energy’s ability to sustain its dividend payout ratio goal; • changes to costs of providing benefits and related funding requirements of pension and OPEB plans due to the market value of the assets that fund the plans, economic conditions, financial market performance, interest rates, timing and form of benefits payments, life expectancies and demographics; • material changes in employee-related benefit and compensation costs, including settlement losses related to pension plans; • risks associated with operation and ownership of non-utility holdings; • changes in technology that alter the channels through which customers buy or utilize Alliant Energy’s, IPL’s or WPL’s products and services; • impacts on equity income from unconsolidated investments from changes in valuations of the assets held, as well as potential changes to ATC’s authorized return on equity; • impacts of IPL’s future tax benefits from Iowa rate-making practices, including deductions for repairs expenditures, allocation of mixed service costs and state depreciation, and recoverability of the associated regulatory assets from customers, when the differences reverse in future periods; • current or future litigation, regulatory investigations, proceedings or inquiries; • reputational damage from negative publicity, protests, fines, penalties and other negative consequences resulting in regulatory and/or legal actions; • the direct or indirect effects resulting from pandemics; • the effect of accounting standards issued periodically by standard-setting bodies; • the ability to successfully complete tax audits and changes in tax accounting methods with no material impact on earnings and cash flows; and • other factors listed in MDA and Risk Factors in Item 1A in the 2023 Form 10-K . Alliant Energy, IPL and WPL each assume no obligation, and disclaim any duty, to update the forward-looking statements in this report, except as required by law. Available Information. Alliant Energy routinely posts important information on its website and considers the Investors section of its website, www.alliantenergy.com/investors , a channel of distribution for material information. Information contained on Alliant Energy’s website is not incorporated herein by reference. 2 Table of Contents PART I. FINANCIAL INFORMATION ITEM 1. CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED) ALLIANT ENERGY CORPORATION CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) For the Three Months Ended March 31, 2024 2023 (in millions, except per share amounts) Revenues: Electric utility $ 791 $ 768 Gas utility 205 276 Other utility 13 11 Non-utility 22 22 Total revenues 1,031 1,077 Operating expenses: Electric production fuel and purchased power 163 157 Electric transmission service 152 146 Cost of gas sold 114 181 Other operation and maintenance 160 174 Depreciation and amortization 189 166 Taxes other than income taxes 31 31 Total operating expenses 809 855 Operating income 222 222 Other (income) and deductions: Interest expense 107 94 Equity income from unconsolidated investments, net ( 15 ) ( 17 ) Allowance for funds used during construction ( 19 ) ( 19 ) Other 1 3 Total other (income) and deductions 74 61 Income before income taxes 148 161 Income tax benefit ( 10 ) ( 2 ) Net income attributable to Alliant Energy common shareowners $ 158 $ 163 Weighted average number of common shares outstanding: Basic 256.2 251.2 Diluted 256.5 251.4 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. 3 Table of Contents ALLIANT ENERGY CORPORATION CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) March 31, 2024 December 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 losses 426 475 Production fuel, at weighted average cost 60 62 Gas stored underground, at weighted average cost 52 79 Materials and supplies, at weighted average cost 208 202 Regulatory assets 218 232 Other 112 160 Total current assets 1,108 1,272 Property, plant and equipment, net 17,354 17,157 Investments: ATC Holdings 392 386 Other 219 216 Total investments 611 602 Other assets: Regulatory assets 2,002 2,029 Deferred charges and other 173 177 Total other assets 2,175 2,206 Total assets $ 21,248 $ 21,237 LIABILITIES AND EQUITY Current liabilities: Current maturities of long-term debt $ 809 $ 809 Commercial paper 334 475 Accounts payable 438 611 Regulatory liabilities 100 107 Other 303 302 Total current liabilities 1,984 2,304 Long-term debt, net (excluding current portion) 8,524 8,225 Other liabilities: Deferred tax liabilities 2,038 2,042 Regulatory liabilities 1,036 1,023 Pension and other benefit obligations 245 249 Other 604 617 Total other liabilities 3,923 3,931 Commitments and contingencies ( Note 1 3 ) 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 outstanding 3 3 Additional paid-in capital 3,033 3,030 Retained earnings 3,791 3,756 Accumulated other comprehensive income 2 1 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 equity 6,817 6,777 Total liabilities and equity $ 21,248 $ 21,237 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 4 Table of Contents ALLIANT ENERGY CORPORATION CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) For the Three Months Ended March 31, 2024 2023 (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 amortization 189 166 Other ( 18 ) ( 6 ) Other changes in assets and liabilities: Accounts receivable ( 116 ) ( 86 ) Gas stored underground 27 68 Derivative assets 30 115 Regulatory assets 35 ( 32 ) Accounts payable 12 ( 97 ) Regulatory liabilities ( 14 ) ( 95 ) Other 4 ( 8 ) Net cash flows from operating activities 307 188 Cash flows used for investing activities: Construction and acquisition expenditures: Utility business ( 478 ) ( 417 ) Other ( 32 ) ( 34 ) Cash receipts on sold receivables 155 173 Proceeds from sale of partial ownership interest in West Riverside — 25 Other 2 ( 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 debt 597 862 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 activities 18 212 Net increase (decrease) in cash, cash equivalents and restricted cash ( 28 ) 137 Cash, cash equivalents and restricted cash at beginning of period 63 24 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. 5 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) For the Three Months Ended March 31, 2024 2023 (in millions) Revenues: Electric utility $ 392 $ 388 Gas utility 108 150 Steam and other 13 11 Total revenues 513 549 Operating expenses: Electric production fuel and purchased power 67 47 Electric transmission service 103 104 Cost of gas sold 60 95 Other operation and maintenance 86 95 Depreciation and amortization 96 96 Taxes other than income taxes 16 16 Total operating expenses 428 453 Operating income 85 96 Other (income) and deductions: Interest expense 42 37 Allowance for funds used during construction ( 10 ) ( 3 ) Other — 1 Total other (income) and deductions 32 35 Income before income taxes 53 61 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. 6 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) March 31, 2024 December 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 losses 204 242 Production fuel, at weighted average cost 29 27 Gas stored underground, at weighted average cost 17 35 Materials and supplies, at weighted average cost 126 122 Regulatory assets 85 93 Other 42 51 Total current assets 515 623 Property, plant and equipment, net 8,450 8,298 Other assets: Regulatory assets 1,482 1,484 Deferred charges and other 85 84 Total other assets 1,567 1,568 Total assets $ 10,532 $ 10,489 LIABILITIES AND EQUITY Current liabilities: Current maturities of long-term debt $ 500 $ 500 Accounts payable 213 262 Accrued taxes 61 50 Accrued interest 49 40 Regulatory liabilities 79 72 Other 97 101 Total current liabilities 999 1,025 Long-term debt, net (excluding current portion) 3,445 3,445 Other liabilities: Deferred tax liabilities 1,098 1,091 Regulatory liabilities 569 572 Pension and other benefit obligations 49 51 Other 335 331 Total other liabilities 2,051 2,045 Commitments and contingencies ( Note 1 3 ) Equity: Interstate Power and Light Company common equity: Common stock - $ 2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding 33 33 Additional paid-in capital 2,937 2,887 Retained earnings 1,067 1,054 Total Interstate Power and Light Company common equity 4,037 3,974 Total liabilities and equity $ 10,532 $ 10,489 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 7 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) For the Three Months Ended March 31, 2024 2023 (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 amortization 96 96 Other ( 11 ) 1 Other changes in assets and liabilities: Accounts receivable ( 119 ) ( 106 ) Gas stored underground 18 34 Derivative assets 20 69 Accounts payable ( 7 ) ( 56 ) Regulatory liabilities 4 ( 59 ) Other 12 ( 27 ) Net cash flows from operating activities 76 24 Cash flows from (used for) investing activities: Construction and acquisition expenditures ( 253 ) ( 101 ) Cash receipts on sold receivables 155 173 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 parent 50 — 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 period 53 15 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. 8 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) For the Three Months Ended March 31, 2024 2023 (in millions) Revenues: Electric utility $ 399 $ 380 Gas utility 97 126 Total revenues 496 506 Operating expenses: Electric production fuel and purchased power 96 109 Electric transmission service 49 42 Cost of gas sold 53 86 Other operation and maintenance 63 66 Depreciation and amortization 90 68 Taxes other than income taxes 14 14 Total operating expenses 365 385 Operating income 131 121 Other (income) and deductions: Interest expense 41 36 Allowance for funds used during construction ( 9 ) ( 16 ) Other 1 1 Total other (income) and deductions 33 21 Income before income taxes 98 100 Income tax expense 6 12 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. 9 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) March 31, 2024 December 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 losses 209 219 Production fuel, at weighted average cost 31 35 Gas stored underground, at weighted average cost 35 44 Materials and supplies, at weighted average cost 78 77 Regulatory assets 133 139 Prepaid gross receipts tax 38 49 Other 19 43 Total current assets 554 613 Property, plant and equipment, net 8,450 8,415 Other assets: Regulatory assets 520 545 Deferred charges and other 57 61 Total other assets 577 606 Total assets $ 9,581 $ 9,634 LIABILITIES AND EQUITY Current liabilities: Commercial paper $ — $ 318 Accounts payable 174 293 Accrued interest 42 40 Regulatory liabilities 21 35 Other 105 89 Total current liabilities 342 775 Long-term debt, net 3,367 3,070 Other liabilities: Deferred tax liabilities 811 827 Regulatory liabilities 467 451 Pension and other benefit obligations 119 121 Other 480 493 Total other liabilities 1,877 1,892 Commitments and contingencies ( Note 1 3 ) Equity: Wisconsin Power and Light Company common equity: Common stock - $ 5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding 66 66 Additional paid-in capital 2,533 2,478 Retained earnings 1,396 1,353 Total Wisconsin Power and Light Company common equity 3,995 3,897 Total liabilities and equity $ 9,581 $ 9,634 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 10 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) For the Three Months Ended March 31, 2024 2023 (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 amortization 90 68 Other ( 11 ) ( 12 ) Other changes in assets and liabilities: Gas stored underground 9 35 Derivative assets 12 46 Regulatory assets 29 ( 37 ) Accounts payable 15 ( 48 ) Derivative liabilities ( 4 ) 28 Regulatory liabilities ( 18 ) ( 35 ) Other 27 52 Net cash flows from operating activities 241 185 Cash flows used for investing activities: Construction and acquisition expenditures ( 225 ) ( 316 ) Proceeds from sale of partial ownership interest in West Riverside — 25 Other 12 ( 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 parent 55 180 Proceeds from issuance of long-term debt 297 297 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 cash 4 81 Cash, cash equivalents and restricted cash at beginning of period 7 5 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. 11 Table of Contents 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 Energy IPL WPL March 31, 2024 December 31, 2023 March 31, 2024 December 31, 2023 March 31, 2024 December 31, 2023 Tax-related $ 939 $ 934 $ 839 $ 831 $ 100 $ 103 Pension and OPEB costs 340 347 168 171 172 176 Assets retired early 267 273 253 259 14 14 Asset retirement obligations (AROs) 200 194 165 160 35 34 Commodity cost recovery 100 120 5 12 95 108 Derivatives 97 102 33 34 64 68 WPL’s Western Wisconsin gas distribution expansion investments 44 44 — — 44 44 IPL’s Duane Arnold Energy Center PPA amendment 36 42 36 42 — — Other 197 205 68 68 129 137 $ 2,220 $ 2,261 $ 1,567 $ 1,577 $ 653 $ 684 Derivatives - Refer to Note 1 0 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 Energy IPL WPL March 31, 2024 December 31, 2023 March 31, 2024 December 31, 2023 March 31, 2024 December 31, 2023 Tax-related $ 563 $ 566 $ 297 $ 299 $ 266 $ 267 Cost of removal obligations 380 366 241 242 139 124 Derivatives 49 65 28 34 21 31 Commodity cost recovery 61 48 25 13 36 35 Other 83 85 57 56 26 29 $ 1,136 $ 1,130 $ 648 $ 644 $ 488 $ 486 12 Table of Contents 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): 2024 2023 Maximum outstanding aggregate cash proceeds $ 79 $ 89 Average outstanding aggregate cash proceeds 24 58 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): March 31, 2024 December 31, 2023 Customer accounts receivable $ 125 $ 130 Unbilled utility revenues 89 98 Other receivables 1 1 Receivables sold to third party 215 229 Less: cash proceeds 18 1 Deferred proceeds 197 228 Less: allowance for expected credit losses 13 12 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): 2024 2023 Collections $ 557 $ 591 Write-offs, net of recoveries 3 2 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): 2024 2023 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, 2024 256,096,848 Shareowner Direct Plan 127,917 Equity-based compensation plans 154,267 Shares outstanding, March 31, 2024 256,379,032 13 Table of Contents Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions): Alliant Energy Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Income (Loss) Trust Equity 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 shareowners 158 158 Common stock dividends ($ 0.48 per share) ( 123 ) ( 123 ) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other ( 3 ) 1 ( 2 ) Other comprehensive income, net of tax 1 1 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 shareowners 163 163 Common stock dividends ($ 0.4525 per share) ( 113 ) ( 113 ) Shareowner Direct Plan issuances 6 6 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 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2024 Beginning balance, December 31, 2023 $ 33 $ 2,887 $ 1,054 $ 3,974 Net income 63 63 Common stock dividends ( 50 ) ( 50 ) Capital contributions from parent 50 50 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 income 72 72 Common stock dividends ( 70 ) ( 70 ) Ending balance, March 31, 2023 $ 33 $ 2,807 $ 970 $ 3,810 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended March 31, 2024 Beginning balance, December 31, 2023 $ 66 $ 2,478 $ 1,353 $ 3,897 Net income 92 92 Common stock dividends ( 49 ) ( 49 ) Capital contributions from parent 55 55 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 income 88 88 Common stock dividends ( 46 ) ( 46 ) Capital contributions from parent 180 180 Ending balance, March 31, 2023 $ 66 $ 2,413 $ 1,234 $ 3,713 14 Table of Contents 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, 2024 Alliant Energy IPL WPL Amount outstanding $ 334 $ — $ — Weighted average interest rates 5.5 % — % — % Available credit facility capacity $ 666 $ 200 $ 300 Alliant Energy IPL WPL Three Months Ended March 31 2024 2023 2024 2023 2024 2023 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 rates 5.5 % 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 Energy IPL WPL Three Months Ended March 31 2024 2023 2024 2023 2024 2023 Electric Utility: Retail - residential $ 297 $ 285 $ 150 $ 143 $ 147 $ 142 Retail - commercial 186 185 114 112 72 73 Retail - industrial 223 216 112 107 111 109 Wholesale 47 46 13 12 34 34 Bulk power and other 38 36 3 14 35 22 Total Electric Utility 791 768 392 388 399 380 Gas Utility: Retail - residential 126 167 68 93 58 74 Retail - commercial 61 88 30 44 31 44 Retail - industrial 5 7 3 4 2 3 Transportation/other 13 14 7 9 6 5 Total Gas Utility 205 276 108 150 97 126 Other Utility: Steam 12 10 12 10 — — Other utility 1 1 1 1 — — Total Other Utility 13 11 13 11 — — Non-Utility and Other: Travero and other 22 22 — — — — Total Non-Utility and Other 22 22 — — — — Total revenues $ 1,031 $ 1,077 $ 513 $ 549 $ 496 $ 506 15 Table of Contents 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 Energy IPL WPL 2024 2023 2024 2023 2024 2023 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 Dates Alliant Energy IPL WPL State net operating losses 2025-2044 $ 403 $ 6 $ 1 Federal tax credits 2032-2044 685 462 214 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 Plans OPEB Plans Alliant Energy 2024 2023 2024 2023 Service cost $ 1 $ 1 $ — $ 1 Interest cost 11 11 2 2 Expected return on plan assets ( 13 ) ( 13 ) ( 1 ) ( 1 ) Amortization of actuarial loss 6 7 — — $ 5 $ 6 $ 1 $ 2 Defined Benefit Pension Plans OPEB Plans IPL 2024 2023 2024 2023 Service cost $ 1 $ 1 $ — $ — Interest cost 5 5 1 1 Expected return on plan assets ( 7 ) ( 7 ) ( 1 ) ( 1 ) Amortization of actuarial loss 2 3 — — $ 1 $ 2 $ — $ — Defined Benefit Pension Plans OPEB Plans WPL 2024 2023 2024 2023 Interest cost $ 5 $ 5 $ 1 $ 1 Expected return on plan assets ( 6 ) ( 5 ) — — Amortization of actuarial loss 3 3 — — $ 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 Energy IPL WPL 2024 2023 2024 2023 2024 2023 Compensation expense $ 4 $ 3 $ 2 $ 2 $ 2 $ 1 Income tax benefits 1 1 1 — — — 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. 16 Table of Contents 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 Grants Grant 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) 140,683 48.40 Restricted stock units 120,557 48.40 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): Electricity FTRs Natural Gas MWhs Years MWhs Years Dths Years Alliant Energy 1,412 2024-2026 4,162 2024 173,746 2024-2032 IPL 673 2024-2026 1,444 2024 78,790 2024-2030 WPL 739 2024-2026 2,718 2024 94,956 2024-2032 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 Energy IPL WPL March 31, 2024 December 31, 2023 March 31, 2024 December 31, 2023 March 31, 2024 December 31, 2023 Current derivative assets $ 16 $ 44 $ 12 $ 30 $ 4 $ 14 Non-current derivative assets 40 44 22 24 18 20 Current derivative liabilities 49 51 23 22 26 29 Non-current derivative liabilities 45 47 7 8 38 39 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. 17 Table of Contents 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 Energy IPL WPL Gross Gross Gross (as reported) Net (as reported) Net (as reported) Net March 31, 2024 Derivative assets $ 56 $ 26 $ 34 $ 17 $ 22 $ 9 Derivative liabilities 94 64 30 13 64 51 December 31, 2023 Derivative assets 88 47 54 32 34 15 Derivative liabilities 98 57 30 8 68 49 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 Energy March 31, 2024 December 31, 2023 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $ 10 $ 10 $ — $ — $ 10 $ 45 $ 45 $ — $ — $ 45 Commodity derivatives 56 — 46 10 56 88 — 59 29 88 Interest rate derivatives 3 — 3 — 3 1 — 1 — 1 Deferred proceeds 184 — — 184 184 216 — — 216 216 Liabilities: Commodity derivatives 94 — 91 3 94 98 — 93 5 98 Long-term debt (incl. current maturities) 9,333 — 9,051 — 9,051 9,034 — 8,677 — 8,677 IPL March 31, 2024 December 31, 2023 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Money market fund investments $ 6 $ 6 $ — $ — $ 6 $ 45 $ 45 $ — $ — $ 45 Commodity derivatives 34 — 26 8 34 54 — 30 24 54 Deferred proceeds 184 — — 184 184 216 — — 216 216 Liabilities: Commodity derivatives 30 — 27 3 30 30 — 25 5 30 Long-term debt (incl. current maturities) 3,945 — 3,607 — 3,607 3,945 — 3,664 — 3,664 18 Table of Contents WPL March 31, 2024 December 31, 2023 Fair Value Fair Value Carrying Level Level Level Carrying Level Level Level Amount 1 2 3 Total Amount 1 2 3 Total Assets: Commodity derivatives $ 22 $ — $ 20 $ 2 $ 22 $ 34 $ — $ 29 $ 5 $ 34 Liabilities: Commodity derivatives 64 — 64 — 64 68 — 68 — 68 Long-term debt 3,367 — 3,176 — 3,176 3,070 — 2,933 — 2,933 Information for fair value measurements using significant unobservable inputs (Level 3 inputs) was as follows (in millions): Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2024 2023 2024 2023 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 ) $ — $ — IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended March 31 2024 2023 2024 2023 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 $ — $ — WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended March 31 2024 2023 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 Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs March 31, 2024 ($ 1 ) $ 8 ($ 1 ) $ 6 $ — $ 2 December 31, 2023 3 21 3 16 — 5 19 Table of Contents 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 Energy IPL WPL Natural gas $ 807 $ 335 $ 472 Coal 167 110 57 Other (a) 124 52 25 $ 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. 20 Table of Contents 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 Energy IPL WPL 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. 21 Table of Contents 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 Energy ATC Holdings, Alliant Utility Non-Utility, Energy Electric Gas Other Total Parent and Other Consolidated (in millions) Three Months Ended March 31, 2024 Revenues $ 791 $ 205 $ 13 $ 1,009 $ 22 $ 1,031 Operating income 164 47 5 216 6 222 Net income attributable to Alliant Energy common shareowners 155 3 158 Three Months Ended March 31, 2023 Revenues $ 768 $ 276 $ 11 $ 1,055 $ 22 $ 1,077 Operating income 163 50 4 217 5 222 Net income attributable to Alliant Energy common shareowners 160 3 163 IPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2024 Revenues $ 392 $ 108 $ 13 $ 513 Operating income 57 22 6 85 Net income 63 Three Months Ended March 31, 2023 Revenues $ 388 $ 150 $ 11 $ 549 Operating income 66 27 3 96 Net income 72 WPL Electric Gas Other Total (in millions) Three Months Ended March 31, 2024 Revenues $ 399 $ 97 $ — $ 496 Operating income (loss) 107 25 ( 1 ) 131 Net income 92 Three Months Ended March 31, 2023 Revenues $ 380 $ 126 $ — $ 506 Operating income 97 23 1 121 Net income 88 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): IPL WPL 2024 2023 2024 2023 Corporate Services billings $ 43 $ 40 $ 40 $ 36 Sales credited — 7 22 13 Purchases billed 96 93 7 15 22 Table of Contents Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL March 31, 2024 December 31, 2023 March 31, 2024 December 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): 2024 2023 ATC billings to WPL $ 37 $ 34 WPL billings to ATC 3 6 WPL owed ATC net amounts of $ 10 million as of March 31, 2024 and $ 10 million as of December 31, 2023. ITEM 2. MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS This MDA includes information relating to Alliant Energy, and IPL and WPL (collectively, the Utilities), as well as ATC Holdings, AEF and Corporate Services. Where appropriate, information relating to a specific entity has been segregated and labeled as such. The following discussion and analysis should be read in conjunction with the Financial Statements and the Notes included in this report, as well as the financial statements, notes and MDA included in the 2023 Form 10-K . Unless otherwise noted, all “per share” references in MDA refer to earnings per diluted share. 2024 HIGHLIGHTS Key highlights since the filing of the 2023 Form 10-K include the following: Customer Investments: • In March 2024, IPL completed construction of the Duane Arnold solar facility (50 MW in Linn County, Iowa). • In March 2024 and April 2024, FERC and the PSCW, respectively, approved the sales of WPL’s partial ownership interests in West Riverside to WEC Energy Group, Inc. (100 MW) and Madison Gas and Electric Company (25 MW). These sales are currently expected to occur in June 2024. • In April 2024, WPL received orders from the PSCW authorizing WPL to construct improvements at the natural gas-fired Neenah Energy Facility and Sheboygan Falls Energy Facility, which would increase the capacity and efficiency of the EGUs. • In April 2024, IPL and WPL entered into agreements to transfer a portion of the renewable tax credits generated in 2024 and 2025 from certain wind, solar and battery storage facilities to other corporate taxpayers in exchange for cash. Rate Matters: • Refer to Note 3 for discussion of WPL’s March 2024 filing for judicial review of PSCW orders related to the recovery and deferral of the return on incremental solar generation construction costs in 2024 and 2025. Environmental Matters: • In April 2024, the EPA issued the final Section 111(d) rule for certain fossil-fueled EGUs and repealed the Affordable Clean Energy rule. The final Section 111(d) rule requires states to implement plans to reduce carbon dioxide emissions through various Best System of Emission Reduction measures at affected sources, including retirement, enforceable limits on operational capacity, co-firing with low-GHG fuels, or carbon capture and storage technology. State plans are subject to EPA approval, and must be submitted within 24 months of the final rule’s effective date, which has not yet been determined. The final rule’s compliance requirements will be phased in beginning in 2030 and covers fossil-fueled EGUs that utilize steam boilers to generate electricity, including IPL’s coal-fired Ottumwa Generating Station, George Neal Generating Station, Prairie Creek Generating Station Unit 3 and Louisa Generating Station, and IPL’s natural gas-fired Burlington Generating Station and Prairie Creek Generating Station Unit 4. The final rule does not apply to EGUs that are retired by January 2032 and is not currently expected to impact WPL’s coal-fired Columbia Energy Center or Edgewater Generating Station given current plans to retire these EGUs prior to this deadline. In addition, the final rule does not impact existing natural gas-fired combustion turbines, including IPL’s Marshalltown Generating Station and Emery Generating Station, and WPL’s Riverside Energy Center and West Riverside Energy Center; however, these EGUs could be subject to future Section 111(d) rules to reduce carbon dioxide emissions from existing combustion turbines. Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these matters, including resolution of ongoing litigation that has been suspended while the EPA revised its regulations. 23 Table of Contents • In April 2024, the EPA issued final revised standards under Section 111(b), which establishes carbon dioxide emissions limits from certain new and reconstructed fossil-fueled EGU combustion turbines that commenced operation after May 23, 2023 with a capacity greater than 25 MW. The final revised standards do not apply to IPL’s Marshalltown Generating Station or WPL’s West Riverside Energy Center, which commenced operation prior to the applicability date of the final revised standards. Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these revised standards, including resolution of ongoing litigation that has been suspended while the EPA revised its regulations. • In April 2024, the EPA issued a final rule that revises discharge limits for specific categories of wastewater from existing coal-fired EGUs. The new limitations will be implemented in each facility’s wastewater discharge permits issued by state agencies and become effective as soon as possible but no later than December 31, 2029. Alliant Energy, IPL and WPL are currently evaluating the final rule and are unable to predict with certainty future compliance impacts. • In April 2024, the EPA issued revisions to the Coal Combustion Residuals Rule, which significantly expand the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities. Alliant Energy, IPL and WPL are currently evaluating the revised Coal Combustion Residuals Rule and are unable to predict with certainty the future outcome or impact of these updates. Legislative Matters: • In May 2024, the Major Economic Growth Attraction program was enacted in Iowa, which offers various tax incentives for up to two qualified businesses for c ertain large-scale projects with capital investments greater than $1 billion constructed on certified sites greater than 250 acres in Iowa. The most significant provision of this program for Alliant Energy encourages economic development in IPL’s service territory. Alliant Energy has various development-ready sites throughout Iowa, including the 1,300-acre Big Cedar Industrial Center Mega-site in Cedar Rapids, Iowa, and the 465-acre Prairie View Industrial Center Super Park in Ames, Iowa. • In May 2024, legislation was enacted in Iowa related to the advance rate-making principles for certain investments in Iowa. The most signification provisions of this legislation for Alliant Energy would allow IPL to include electric storage and nuclear-fired generation projects in the advance rate-making principles request process prior to making these investments in Iowa, and require IPL to obtain a certificate of public convenience, use and necessity (GCU Certificate) from the IUB in order to construct electric storage projects. RESULTS OF OPERATIONS Financial Results Overview - The table below includes EPS for Utilities and Corporate Services, ATC Holdings, and Non-utility and Parent, which are non-GAAP financial measures. Alliant Energy believes these non-GAAP financial measures are useful to investors because they facilitate an understanding of segment performance and trends, and provide additional information about Alliant Energy’s operations on a basis consistent with the measures that management uses to manage its operations and evaluate its performance. Alliant Energy’s net income and EPS attributable to Alliant Energy common shareowners for the three months ended March 31 were as follows (dollars in millions, except per share amounts): 2024 2023 Income (Loss) EPS Income (Loss) EPS Utilities and Corporate Services $159 $0.62 $163 $0.65 ATC Holdings 9 0.04 9 0.04 Non-utility and Parent (10) (0.04) (9) (0.04) Alliant Energy Consolidated $158 $0.62 $163 $0.65 Alliant Energy’s Utilities and Corporate Services net income decreased by $4 million for the three-month period, primarily due to lower retail electric and gas sales due to impacts of warmer than normal temperatures during the three months ended March 31, 2024, and higher financing and depreciation expenses. These items were partially offset by higher revenue requirements from WPL’s capital investments. 24 Table of Contents Net Income Variances - The following items contributed to increased (decreased) net income for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Revenues: Changes in electric utility (Refer to details below ) $23 $4 $19 Changes in gas utility (Refer to details below ) (71) (42) (29) Changes in other utility 2 2 — Changes in total revenues (46) (36) (10) Operating expenses: Changes in electric production fuel and purchased power (Refer to details below ) (6) (20) 13 Changes in electric transmission service (6) 1 (7) Changes in cost of gas sold (Refer to details below ) 67 35 33 Changes in other operation and maintenance (Refer to details below ) 14 9 3 Changes in depreciation and amortization (Higher primarily due to WPL’s solar generation placed in service in 2023, as well as WPL’s amortization of liquidated damages related to West Riverside procurement contracts, which resulted in reductions to depreciation and amortization expenses in the first quarter of 2023) (23) — (22) Changes in total operating expenses 46 25 20 Changes in operating income — (11) 10 Other income and deductions: Changes in interest expense (Higher primarily due to financings completed in 2024 and 2023) (13) (5) (5) Changes in equity income from unconsolidated investments, net (Refer to Note 5 for details) (2) — — Changes in AFUDC (Primarily due to changes in levels of CWIP balances related to solar generation and battery storage) — 7 (7) Changes in Other 2 1 — Changes in total other income and deductions (13) 3 (12) Changes in income before income taxes (13) (8) (2) Changes in income taxes (Refer to Note 9 for details) 8 (1) 6 Changes in net income ($5) ($9) $4 Electric and Gas Revenues and Sales Summary - Electric and gas revenues (in millions), and MWh and Dth sales (in thousands), for the three months ended March 31 were as follows: Alliant Energy Electric Gas Revenues MWhs Sold Revenues Dths Sold 2024 2023 2024 2023 2024 2023 2024 2023 Retail $706 $686 5,989 6,201 $192 $262 20,117 22,310 Sales for resale: Wholesale 47 46 679 698 N/A N/A N/A N/A Bulk power and other 21 23 1,670 1,243 N/A N/A N/A N/A Transportation/Other 17 13 15 15 13 14 33,908 32,614 $791 $768 8,353 8,157 $205 $276 54,025 54,924 IPL Electric Gas Revenues MWhs Sold Revenues Dths Sold 2024 2023 2024 2023 2024 2023 2024 2023 Retail $376 $362 3,365 3,544 $101 $141 10,205 11,459 Sales for resale: Wholesale 13 12 182 187 N/A N/A N/A N/A Bulk power and other (3) 7 324 496 N/A N/A N/A N/A Transportation/Other 6 7 8 8 7 9 11,695 12,035 $392 $388 3,879 4,235 $108 $150 21,900 23,494 25 Table of Contents WPL Electric Gas Revenues MWhs Sold Revenues Dths Sold 2024 2023 2024 2023 2024 2023 2024 2023 Retail $330 $324 2,624 2,657 $91 $121 9,912 10,851 Sales for resale: Wholesale 34 34 497 511 N/A N/A N/A N/A Bulk power and other 24 16 1,346 747 N/A N/A N/A N/A Transportation/Other 11 6 7 7 6 5 22,213 20,579 $399 $380 4,474 3,922 $97 $126 32,125 31,430 Sales Trends and Temperatures - Alliant Energy’s retail electric sales volumes decreased 3% for the three months ended March 31, 2024 compared to the same period in 2023, primarily due to changes in sales volumes to industrial customers due to standby service customers that can use other generation and changes in temperatures, partially offset by an additional day of sales due to leap year in 2024. Alliant Energy’s retail gas sales volumes decreased 10% for the three months ended March 31, 2024 compared to the same period in 2023, primarily due to changes in temperatures, partially offset by an additional day of sales due to leap year in 2024. Estimated decreases to operating income from the impacts of temperatures for the three months ended March 31 were as follows (in millions): Electric Gas 2024 2023 Change 2024 2023 Change IPL ($9) ($4) ($5) ($6) ($3) ($3) WPL (10) (5) (5) (5) (3) (2) Total Alliant Energy ($19) ($9) ($10) ($11) ($6) ($5) Electric Sales for Resale - Bulk Power and Other - Bulk power and other volume changes were due to changes in sales in the wholesale energy markets operated by MISO. These changes are impacted by several factors, including the availability and dispatch of Alliant Energy’s EGUs and electricity demand within these wholesale energy markets. Changes in bulk power and other revenues were largely offset by changes in fuel-related costs, and therefore did not have a significant impact on operating income. Gas Transportation/Other - Gas transportation/other sales volume changes were largely due to changes in the gas volumes supplied to Alliant Energy’s natural gas-fired EGUs caused by the availability and dispatch of such EGUs. Electric Utility Revenue Variances - The following items contributed to increased (decreased) electric utility revenues for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Higher revenue requirements at WPL (a) $38 $— $38 Estimated changes in sales volumes caused by temperatures (10) (5) (5) Higher (lower) sales for resale bulk power and other revenues (2) (10) 8 Higher (lower) revenues due to changes in retail electric fuel-related costs (Refer to Electric Production Fuel and Purchased Power Expenses Variances below) (a) (1) 26 (27) Other (2) (7) 5 $23 $4 $19 (a) In December 2023, the PSCW issued an order authorizing an annual base rate increase of $49 million for WPL’s retail electric customers, covering the 2024 forward-looking Test Period, which reflects revenue requirement impacts of increasing electric rate base and lower forecasted fuel-related expenses. Gas Utility Revenue Variances - The following items contributed to increased (decreased) gas utility revenues for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Lower revenues due to changes in gas costs (Refer to Cost of Gas Sold Expense Variances below) ($67) ($35) ($33) Estimated changes in sales volumes caused by temperatures (5) (3) (2) Higher revenue requirements at WPL (a) 5 — 5 Other (4) (4) 1 ($71) ($42) ($29) 26 Table of Contents (a) In December 2023, the PSCW issued an order authorizing an annual base rate increase of $13 million for WPL’s retail gas customers, covering the 2024 forward-looking Test Period, which reflects revenue requirement impacts of increasing gas rate base. Electric Production Fuel and Purchased Power Expenses Variances - The following items contributed to (increased) decreased electric production fuel and purchased power expenses for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Lower electric production fuel costs (a) $53 $38 $15 Changes in regulatory recovery of retail electric fuel-related costs (31) (38) 7 Higher purchased power expense (b) (27) (20) (7) Other (1) — (2) ($6) ($20) $13 (a) Electric production fuel costs decreased primarily due to lower natural gas prices in the first quarter of 2024 compared to the same period in 2023 and lower natural gas volumes due to lower dispatch of IPL’s natural gas-fired EGUs in 2024, partially offset by higher coal volumes due to higher dispatch of WPL’s coal-fired EGUs in 2024. (b) Purchased power expense increased primarily due to higher prices for electricity purchased by IPL and WPL. Cost of Gas Sold Expense Variances - The following items contributed to (increased) decreased cost of gas sold expense for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Lower natural gas prices and lower retail gas volumes primarily due to changes in temperatures $75 $50 $25 Changes in the regulatory recovery of gas costs (6) (14) 8 Other (2) (1) — $67 $35 $33 Other Operation and Maintenance Expenses Variances - The following items contributed to (increased) decreased other operation and maintenance expenses for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Lower generation and energy delivery expenses $8 $1 $7 Lower energy efficiency expense at IPL (mostly offset by higher revenues) 7 7 — Other (1) 1 (4) $14 $9 $3 LIQUIDITY AND CAPITAL RESOURCES The liquidity and capital resources summary included in the 2023 Form 10-K has not changed materially, except as described below. Liquidity Position - At March 31, 2024, Alliant Energy had $32 million of cash and cash equivalents, $666 million ($166 million at the parent company, $200 million at IPL and $300 million at WPL) of available capacity under the single revolving credit facility and $92 million of available capacity at IPL under its sales of accounts receivable program. Capital Structure - Capital structures at March 31, 2024 were as follows (Long-term Debt (including current maturities) (LD); Short-term Debt (SD); Common Equity (CE)): 27 Table of Contents Cash Flows - Selected information from the cash flows statements was as follows (in millions): Alliant Energy IPL WPL 2024 2023 2024 2023 2024 2023 Cash, cash equivalents and restricted cash, January 1 $63 $24 $53 $15 $7 $5 Cash flows from (used for): Operating activities 307 188 76 24 241 185 Investing activities (353) (263) (107) 70 (213) (295) Financing activities 18 212 (10) (74) (24) 191 Net increase (decrease) (28) 137 (41) 20 4 81 Cash, cash equivalents and restricted cash, March 31 $35 $161 $12 $35 $11 $86 Operating Activities - The following items contributed to increased (decreased) operating activity cash flows for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Higher collections from WPL’s retail electric and gas base rate increases $43 $— $43 Changes in the sales of accounts receivable at IPL 18 18 — Decreased collections from IPL’s and WPL’s retail customers caused by temperature impacts on electric and gas sales (15) (8) (7) Other (primarily due to other changes in working capital) 73 42 20 $119 $52 $56 Investing Activities - The following items contributed to increased (decreased) investing activity cash flows for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL (Higher) lower utility construction and acquisition expenditures (a) ($61) ($152) $91 Proceeds from sale of partial ownership interest in West Riverside in 2023 (25) — (25) Changes in the amount of cash receipts on sold receivables (18) (18) — Other 14 (7) 16 ($90) ($177) $82 (a) Largely due to higher expenditures for IPL’s solar generation and WPL’s battery storage, partially offset by lower expenditures for WPL’s solar generation. Financing Activities - The following items contributed to increased (decreased) financing activity cash flows for the three months ended March 31, 2024 compared to the same period in 2023 (in millions): Alliant Energy IPL WPL Higher payments to retire long-term debt ($300) $— $— Lower net proceeds from issuance of long-term debt (265) — — (Higher) lower common stock dividends (10) 20 (3) Higher (lower) capital contributions from IPL’s and WPL’s parent company, Alliant Energy — 50 (125) Net changes in the amount of commercial paper and other short-term borrowings outstanding 391 — (88) Other (10) (6) 1 ($194) $64 ($215) Common Stock Issuances - Refer to Note 6 for discussion of common stock issuances by Alliant Energy in 2024. Long-term Debt - Refer to Note 7 (b) for discussion of various issuances and/or retirements of long-term debt by AEF and WPL in 2024. Impact of Credit Ratings on Liquidity and Collateral Obligations - Ratings Triggers - In March 2024, Standard & Poor’s Ratings Services changed Alliant Energy’s and IPL’s outlooks from stable to negative. These outlook changes are not expected to have a material impact on Alliant Energy’s and IPL’s liquidity or collateral obligations. Off-Balance Sheet Arrangements and Certain Financial Commitments - A summary of Alliant Energy’s and IPL’s off-balance sheet arrangements and Alliant Energy’s, IPL’s and WPL’s contractual obligations is included in the 2023 Form 10-K and has not changed materially from the items reported in the 2023 Form 10-K , except for the items described in Notes 4 , 7 and 1 3 . 28 Table of Contents OTHER MATTERS Critical Accounting Estimates - The summary of critical accounting estimates included in the 2023 Form 10-K has not changed materially, except as described below. Long-Lived Assets - Regulated Operations - Solar Generation Projects Recently Completed or Under Construction - Alliant Energy and WPL currently expect construction costs associated with WPL’s 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. ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK Quantitative and Qualitative Disclosures About Market Risk are reported in the 2023 Form 10-K and have not changed materially. ITEM 4. CONTROLS AND PROCEDURES Alliant Energy’s, IPL’s and WPL’s management evaluated, with the participation of each of Alliant Energy’s, IPL’s and WPL’s Chief Executive Officer, Chief Financial Officer and Disclosure Committee, the effectiveness of the design and operation of Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures (as defined in Rule 13a-15(e) of the Securities Exchange Act of 1934, as amended) as of March 31, 2024 pursuant to the requirements of the Securities Exchange Act of 1934, as amended. Based on their evaluation, the Chief Executive Officer and the Chief Financial Officer concluded that Alliant Energy’s, IPL’s and WPL’s disclosure controls and procedures were effective as of the quarter ended March 31, 2024. There was no change in Alliant Energy’s, IPL’s and WPL’s internal control over financial reporting that occurred during the quarter ended March 31, 2024 that has materially affected, or is reasonably likely to materially affect, Alliant Energy’s, IPL’s or WPL’s internal control over financial reporting. PART II. OTHER INFORMATION ITEM 1. LEGAL PROCEEDINGS None. SEC regulations require Alliant Energy, IPL and WPL to disclose information about certain proceedings arising under federal, state or local environmental provisions when a governmental authority is a party to the proceedings and such proceedings involve potential monetary sanctions that Alliant Energy, IPL and WPL reasonably believe will exceed a specified threshold. Pursuant to the SEC regulations, Alliant Energy, IPL and WPL use a threshold of $1 million for purposes of determining whether disclosure of any such proceedings is required. Applying this threshold, there are no environmental matters to disclose for this period. ITEM 1A. RISK FACTORS The risk factors described in Item 1A in the 2023 Form 10-K have not changed materially. ITEM 2. UNREGISTERED SALES OF EQUITY SECURITIES AND USE OF PROCEEDS A summary of Alliant Energy common stock repurchases for the quarter ended March 31, 2024 was as follows: Total Number Average Price Total Number of Shares Maximum Number (or Approximate of Shares Paid Per Purchased as Part of Dollar Value) of Shares That May Period Purchased (a) Share Publicly Announced Plan Yet Be Purchased Under the Plan (a) January 1 through January 31 6,936 $50.38 — N/A February 1 through February 29 3,393 48.40 — N/A March 1 through March 31 439 47.87 — N/A 10,768 49.65 — 29 Table of Contents (a) All shares were purchased on the open market and held in a rabbi trust under the Alliant Energy Deferred Compensation Plan. There is no limit on the number of shares of Alliant Energy common stock that may be held under the Deferred Compensation Plan, which currently does not have an expiration date. ITEM 5. OTHER INFORMATION (c) During the quarter ended March 31, 2024, no director or officer of Alliant Energy, IPL or WPL adopted or terminated a Rule 10b5-1 trading arrangement or non-Rule 10b5-1 trading arrangement, as each term is defined in Item 408(a) of Regulation S-K . ITEM 6. EXHIBITS The following Exhibits are filed herewith or incorporated herein by reference. Exhibit Number Description 4.1 Officers’ Certificate, dated as of March 7, 2024, creating WPL’s 5.375% Debentures due March 30, 2034 (incorporated by reference to Exhibit 4.1 to WPL’s Form 8-K, filed March 7, 2024 (File No. 0-337)) 10.1 Amended and Restated Term Loan Credit Agreement, dated as of March 1, 2024, among AEF, Alliant Energy, U.S. Bank N ational A ssociation and the lender parties set forth therein (incorporated by reference to Exhibit 10.1 to Alliant Energy’s Form 8-K, filed March 5, 2024 (File No. 1-9894)) 31.1 Certification of the Chief Executive Officer for Alliant Energy 31.2 Certification of the Chief Financial Officer for Alliant Energy 31.3 Certification of the Chief Executive Officer for IPL 31.4 Certification of the Chief Financial Officer for IPL 31.5 Certification of the Chief Executive Officer for WPL 31.6 Certification of the Chief Financial Officer for WPL 32.1 Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for Alliant Energy 32.2 Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for IPL 32.3 Written Statement of the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C.§1350 for WPL 101.INS Inline XBRL Instance Document - the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document 101.SCH Inline XBRL Taxonomy Extension Schema Document 101.CAL Inline XBRL Taxonomy Extension Calculation Linkbase Document 101.LAB Inline XBRL Taxonomy Extension Label Linkbase Document 101.PRE Inline XBRL Taxonomy Extension Presentation Linkbase Document 101.DEF Inline XBRL Taxonomy Extension Definition Linkbase Document 104 Cover Page Interactive Data File (embedded within the Inline XBRL document) SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company have each duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized on the 3rd day of May 2024. ALLIANT ENERGY CORPORATION Registrant By: /s/ Benjamin M. Bilitz Chief Accounting Officer and Controller Benjamin M. Bilitz (Principal Accounting Officer and Authorized Signatory) INTERSTATE POWER AND LIGHT COMPANY Registrant By: /s/ Benjamin M. Bilitz Chief Accounting Officer and Controller Benjamin M. Bilitz (Principal Accounting Officer and Authorized Signatory) WISCONSIN POWER AND LIGHT COMPANY Registrant By: /s/ Benjamin M. Bilitz Chief Accounting Officer and Controller Benjamin M. Bilitz (Principal Accounting Officer and Authorized Signatory) 30