ALLIANT ENERGY CORP 10-Q

lnt-20260630 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 June 30, 2026 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 June 30, 2026: Alliant Energy Corporation, Common Stock, $0.01 par value, 259,284,699 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 Forward-looking Statements 1 Part I. Financial Information 4 Item 1. Condensed Consolidated Financial Statements (Unaudited) 4 Alliant Energy Corporation 4 Interstate Power and Light Company 7 Wisconsin Power and Light Company 10 Combined Notes to Condensed Consolidated Financial Statements 13 1. Summary of Significant Accounting Policies 13 2. Regulatory Matters 13 3 . Receivables 14 4 . Investments 15 5 . Common Equity 15 6 . Debt 18 7 . Revenues 19 8 . Income Taxes 20 9 . Benefit Plans 21 1 0 . Derivative Instruments 22 1 1 . Fair Value Measurements 23 1 2 . Commitments and Contingencies 25 1 3 . Segments of Business 27 1 4 . Related Parties 29 Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations 30 Item 3. Quantitative and Qualitative Disclosures About Market Risk 38 Item 4. Controls and Procedures 38 Part II. Other Information 38 Item 1. Legal Proceedings 38 Item 1A. Risk Factors 39 Item 2. Unregistered Sales of Equity Securities and Use of Proceeds 39 Item 5. Other Information 39 Item 6. Exhibits 40 Signatures 40 DEFINITIONS The following abbreviations or acronyms used in this report are defined below: Abbreviation or Acronym Definition Abbreviation or Acronym Definition 2025 Form 10-K Combined Annual Report on Form 10-K filed by Alliant Energy, IPL and WPL for the year ended Dec. 31, 2025 IPL Interstate Power and Light Company AEF Alliant Energy Finance, LLC IUC Iowa Utilities Commission Alliant Energy Alliant Energy Corporation MDA Management’s Discussion and Analysis of Financial Condition and Results of Operations ATC American Transmission Company LLC MISO Midcontinent Independent System Operator, Inc. ATC Holdings Interest in American Transmission Company LLC and ATC Holdco LLC MW Megawatt Corporate Services Alliant Energy Corporate Services, Inc. MWh Megawatt-hour Dth Dekatherm N/A Not applicable EPA U.S. Environmental Protection Agency Note(s) Combined Notes to Condensed Consolidated Financial Statements EPS Earnings per weighted average common share PSCW Public Service Commission of Wisconsin Financial Statements Condensed Consolidated Financial Statements SEC Securities and Exchange Commission FTR Financial transmission right U.S. United States of America GAAP U.S. generally accepted accounting principles WPL Wisconsin Power and Light Company Table of Contents 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: • IPL’s and WPL’s ability to obtain adequate and timely rate relief to allow for, among other things, recovery of and/or the return on costs, including fuel costs, operating costs, transmission costs, capacity costs, costs of cancelled generation projects incurred prior to pursuing regulatory approval, including costs incurred for generation projects that are delayed, modified or no longer pursued due to changes in resource needs or plans, as well as costs of generation projects incurred prior to regulatory approval or that exceed initial estimates, deferred expenditures, deferred tax assets, tax expense, interest expense, capital expenditures, marginal costs to service new customers, and remaining costs related to electric generating units (EGUs) that have been or may be permanently closed and certain other retired assets, environmental remediation costs, and decreases in sales volumes, as well as earning their authorized rates of return, payments to their parent of expected levels of dividends, the impact of rate design on current and potential customers and demand for energy in their service territories, and the ability to obtain regulatory approval with acceptable conditions for individual customer rates for large load growth customers and WPL’s large load tariff; • the impact of IPL’s retail electric base rate moratorium; • the ability to obtain regulatory approval for constr uction projects with acceptable conditions; • the ability to complete construction of generation and energy storage projects by planned in-service dates, with the expected earnings contributions 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, including previously exempted tariffs related to solar project materials and equipment from certain countries, duties or other assessments, including antidumping or countervailing duties, inflation, labor issues or supply shortages, supply chain disruptions which may result from geopolitical issues, contractor performance, the ability to successfully resolve warranty issues or contract disputes, the ability to obtain adequate generator interconnection agreements to connect the new projects to MISO in a timely manner, the ability to obtain siting and environmental permits from local and state agencies and the ability of ITC Midwest LLC (ITC) and ATC to complete transmission upgrades in a timely manner; • weather effects on utility sales volumes and operations; • 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 and other non-traditional service models, including alternative electric suppliers and potential policy changes, regulatory changes, or legislation that may enable large customers to source behind-the-meter generation directly from third parties or to own or otherwise procure on-site or behind-the-meter generation or participate in co-located resource arrangements, in IPL’s and WPL’s service territories on system reliability, operating expenses and customers’ demand for electricity; • economic conditions in IPL’s and WPL’s service territories, including the potential impacts of business or facility closures and tariffs; • the ability and cost to attract large load growth customers and to provide sufficient generation and the ability of ITC and ATC to provide sufficient transmission capacity for potential load growth timely, including significant new commercial or industrial customers, such as data centers; • the ability of potential large load growth customers to timely construct new facilities, due to local or state regulatory actions, zoning, siting, or permitting actions, public or community opposition or other factors, as well as the resulting higher system load demand by expected levels and timeframes; • the impact of large load growth customers altering, delaying or cancelling planned facilities, including any resulting impacts of overbuilt or under-utilized transmission capacity or generation and energy storage assets; • 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 and gas services and their ability to pay their bills; • changes in the price of delivered natural gas, transmission, purchased electric energy, purchased electric capacity 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; • the ability to achieve the expected level of tax benefits for renewable generation and energy storage projects based on tax guidelines, timely beginning of construction and in-service dates, sourcing permissible amounts of construction and/or financing support from entities with ties to certain foreign countries, compliance with prevailing wage and apprenticeship requirements, project costs and the level of electricity output generated by qualifying generating facilities, and the ability to efficiently utilize the renewable generation and energy storage project tax benefits to achieve IPL’ s authorized rate of return and for the benefit of IPL’s and WPL’s customers; • federal and state regulatory or governmental actions, including the impact of legislation, Treasury regulations, executive orders, interpretations and guidance, and changes in public policy, including changes impacting renewable tax credits, including any repeal, modification, or reduced funding of the Inflation Reduction Act and the One Big Beautiful Bill Act, and siting generation and energy storage projects; • 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; 1 Table of Contents • the impacts of changes in the tax code, including tax rates, minimum tax rates, adjustments made to deferred tax assets and liabilities, changes in state income tax apportionment, and changes impacting the availability of and ability to transfer renewable tax credits, including preserving the qualification of any future tax credits; • disruptions to ongoing operations and the supply of materials, services, equipment and commodities needed to continue to operate and maintain existing assets and to construct capital projects, which may result from geopolitical issues, tariffs, 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; • continued access to the capital markets on competitive terms and rates, and risks associated with potential increases in borrowing costs or reduced access to funding, and the actions of credit rating agencies; • the future development of technologies related to electrification, and the ability to reliably store and manage electricity; • 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 large load growth customers, 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; • changes to MISO’s interconnection or resource adequacy process establishing capacity planning reserve margin and capacity accreditation requirements that may impact how and when new and existing generating and energy storage facilities 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 to procure capacity in the market whereby such costs might not be recovered in rates; • any legislative or regulatory changes that impose mandatory integrated resource planning requirements or materially modify existing planning processes, potentially affecting resource selection, cost recovery, and the ability to meet large load growth demand for energy; • any material post-closing payments related to any past asset divestitures, including the transfer of renewable tax credits, which could result from, among other things, indemnification agreements, warranties, guarantees or litigation; • issues associated with environmental remediation and environmental compliance, including compliance with all current environmental and emissions laws, regulations, siting requirements, and 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 emissions reductions, including greenhouse gases (GHG), 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 GHG emissions; • the timely development of technologies, innovations and advancements to provide cost effective alternatives to traditional energy sources; • 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, disruptions in telecommunications, technological 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 and energy storage facilities, including start-up risks, breakdown or failure of equipment, fires, 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, capacity, 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 other postretirement benefits (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, including potential impairments and risks associated with valuation changes of investments; • changes in technology that alter the channels through which customers buy or utilize Alliant Energy’s, IPL’s or WPL’s products and services; • risks associated with third-party risk management practices, including vendor financial condition, operational performance, cybersecurity incidents, and compliance with contractual and regulatory requirements; 2 Table of Contents • risks associated with large-scale internal technology modernization initiatives, including enterprise asset management systems, operational technology/informational technology integration, cloud transformation, and digital modernization, and the potential for delays, cost overruns, or operational impacts; • 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 and cost of removal obligations, 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 2025 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. 3 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 For the Six Months Ended June 30, Ended June 30, 2026 2025 2026 2025 (in millions, except per share amounts) Revenues: Electric utility $ 861 $ 851 $ 1,748 $ 1,703 Gas utility 82 76 353 316 Other utility 2 11 5 25 Non-utility 26 23 49 44 Total revenues 971 961 2,155 2,088 Operating expenses: Electric production fuel and purchased power 132 150 301 325 Electric transmission service 155 151 314 308 Cost of gas sold 37 30 210 167 Other operation and maintenance 209 168 390 327 Depreciation and amortization 220 208 442 420 Taxes other than income taxes 33 31 64 62 Total operating expenses 786 738 1,721 1,609 Operating income 185 223 434 479 Other (income) and deductions: Interest expense 143 124 285 243 Equity income from unconsolidated investments, net ( 43 ) ( 10 ) ( 65 ) ( 23 ) Allowance for funds used during construction ( 31 ) ( 23 ) ( 61 ) ( 41 ) Other ( 2 ) 1 ( 5 ) 4 Total other (income) and deductions 67 92 154 183 Income before income taxes 118 131 280 296 Income tax benefit ( 52 ) ( 43 ) ( 114 ) ( 91 ) Net income attributable to Alliant Energy common shareowners $ 170 $ 174 $ 394 $ 387 Weighted average number of common shares outstanding: Basic 258.5 256.9 257.9 256.8 Diluted 260.9 257.3 259.9 257.3 Earnings per weighted average common share attributable to Alliant Energy common shareowners: Basic $ 0.66 $ 0.68 $ 1.53 $ 1.51 Diluted $ 0.65 $ 0.68 $ 1.52 $ 1.50 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 4 Table of Contents ALLIANT ENERGY CORPORATION CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) June 30, 2026 December 31, 2025 (in millions, except per share and share amounts) ASSETS Current assets: Cash and cash equivalents $ 25 $ 556 Accounts receivable, less allowance for expected credit losses 381 476 Production fuel, at weighted average cost 60 46 Gas stored underground, at weighted average cost 30 49 Materials and supplies, at weighted average cost 208 193 Regulatory assets 172 155 Income taxes receivable 40 12 Other 284 210 Total current assets 1,200 1,697 Property, plant and equipment, net 21,058 20,344 Investments: ATC Holdings 501 463 Other 255 231 Total investments 756 694 Other assets: Regulatory assets 2,139 2,119 Deferred charges and other 165 137 Total other assets 2,304 2,256 Total assets $ 25,318 $ 24,991 LIABILITIES AND EQUITY Current liabilities: Current maturities of long-term debt $ 374 $ 1,074 Commercial paper 708 88 Other short-term borrowings 400 — Accounts payable 628 498 Accrued interest 116 124 Regulatory liabilities 80 88 Other 268 251 Total current liabilities 2,574 2,123 Long-term debt, net (excluding current portion) 10,636 10,954 Other liabilities: Deferred tax liabilities 2,360 2,310 Regulatory liabilities 1,049 1,113 Pension and other benefit obligations 157 173 Other 1,013 984 Total other liabilities 4,579 4,580 Commitments and contingencies ( Note 1 2 ) Equity: Alliant Energy Corporation common equity: Common stock - $ 0.01 par value - 480,000,000 shares authorized; 259,284,699 and 257,137,261 shares outstanding 3 3 Additional paid-in capital 3,174 3,101 Retained earnings 4,363 4,243 Accumulated other comprehensive income 3 1 Shares in deferred compensation trust - 351,469 and 367,338 shares at a weighted average cost of $ 40.46 and $ 39.05 per share ( 14 ) ( 14 ) Total Alliant Energy Corporation common equity 7,529 7,334 Total liabilities and equity $ 25,318 $ 24,991 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 5 Table of Contents ALLIANT ENERGY CORPORATION CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) For the Six Months Ended June 30, 2026 2025 (in millions) Cash flows from operating activities: Net income $ 394 $ 387 Adjustments to reconcile net income to net cash flows from operating activities: Depreciation and amortization 442 420 Deferred tax benefit and tax credits ( 94 ) ( 100 ) Equity income from unconsolidated investments, net ( 65 ) ( 23 ) Other 34 22 Other changes in assets and liabilities: Accounts receivable ( 183 ) ( 289 ) Derivative assets ( 55 ) ( 29 ) Regulatory liabilities 1 71 Deferred income taxes (a) 87 86 Other ( 80 ) ( 53 ) Net cash flows from operating activities 481 492 Cash flows used for investing activities: Construction and acquisition expenditures: Utility business ( 913 ) ( 976 ) Other ( 109 ) ( 89 ) Cash receipts on sold receivables 264 198 Other ( 37 ) ( 27 ) Net cash flows used for investing activities ( 795 ) ( 894 ) Cash flows from (used for) financing activities: Common stock dividends ( 274 ) ( 261 ) Proceeds from issuance of common stock, net 70 12 Proceeds from issuance of long-term debt — 1,162 Proceeds from issuance of other short-term borrowings 400 — Payments to retire long-term debt ( 1,075 ) — Net change in commercial paper 670 ( 266 ) Other ( 8 ) 3 Net cash flows from (used for) financing activities ( 217 ) 650 Net increase (decrease) in cash, cash equivalents and restricted cash ( 531 ) 248 Cash, cash equivalents and restricted cash at beginning of period 556 81 Cash, cash equivalents and restricted cash at end of period $ 25 $ 329 Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 293 ) ($ 239 ) Income taxes, net (a) $ 96 $ 91 Significant non-cash investing and financing activities: Accrued capital expenditures $ 279 $ 204 Beneficial interest obtained in exchange for securitized accounts receivable $ 95 $ 235 (a) 2026 and 2025 include $ 102 million and $ 97 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers. Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 6 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) For the Three Months For the Six Months Ended June 30, Ended June 30, 2026 2025 2026 2025 (in millions) Revenues: Electric utility $ 431 $ 418 $ 867 $ 848 Gas utility 43 40 166 158 Steam and other 1 11 3 24 Total revenues 475 469 1,036 1,030 Operating expenses: Electric production fuel and purchased power 45 40 110 107 Electric transmission service 98 100 202 207 Cost of gas sold 22 17 96 81 Other operation and maintenance 108 84 195 169 Depreciation and amortization 119 115 239 230 Taxes other than income taxes 16 15 30 29 Total operating expenses 408 371 872 823 Operating income 67 98 164 207 Other (income) and deductions: Interest expense 57 52 114 99 Allowance for funds used during construction ( 21 ) ( 13 ) ( 40 ) ( 22 ) Other ( 1 ) ( 2 ) ( 3 ) ( 2 ) Total other (income) and deductions 35 37 71 75 Income before income taxes 32 61 93 132 Income tax benefit ( 33 ) ( 37 ) ( 66 ) ( 77 ) Net income $ 65 $ 98 $ 159 $ 209 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. 7 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) June 30, 2026 December 31, 2025 (in millions, except per share and share amounts) ASSETS Current assets: Cash and cash equivalents $ 12 $ 7 Accounts receivable, less allowance for expected credit losses 117 185 Production fuel, at weighted average cost 25 18 Gas stored underground, at weighted average cost 12 24 Materials and supplies, at weighted average cost 118 111 Regulatory assets 65 59 Other 94 58 Total current assets 443 462 Property, plant and equipment, net 10,808 10,436 Other assets: Regulatory assets 1,582 1,557 Deferred charges and other 39 40 Total other assets 1,621 1,597 Total assets $ 12,872 $ 12,495 LIABILITIES AND EQUITY Current liabilities: Commercial paper $ 77 $ 88 Accounts payable 302 232 Accounts payable to associated companies 47 45 Accrued taxes 66 53 Accrued interest 46 47 Regulatory liabilities 34 41 Other 89 80 Total current liabilities 661 586 Long-term debt, net 4,732 4,680 Other liabilities: Deferred tax liabilities 1,314 1,278 Regulatory liabilities 517 545 Pension and other benefit obligations 26 30 Other 549 532 Total other liabilities 2,406 2,385 Commitments and contingencies ( Note 1 2 ) 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 3,647 3,497 Retained earnings 1,393 1,314 Total Interstate Power and Light Company common equity 5,073 4,844 Total liabilities and equity $ 12,872 $ 12,495 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 8 Table of Contents INTERSTATE POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) For the Six Months Ended June 30, 2026 2025 (in millions) Cash flows from operating activities: Net income $ 159 $ 209 Adjustments to reconcile net income to net cash flows from operating activities: Depreciation and amortization 239 230 Deferred tax benefit and tax credits ( 59 ) ( 59 ) Other ( 28 ) ( 14 ) Other changes in assets and liabilities: Accounts receivable ( 218 ) ( 273 ) Derivative assets ( 41 ) ( 21 ) Regulatory assets ( 42 ) ( 47 ) Accounts payable 38 7 Deferred income taxes (a) 70 98 Other 22 ( 22 ) Net cash flows from operating activities 140 108 Cash flows used for investing activities: Construction and acquisition expenditures ( 491 ) ( 628 ) Cash receipts on sold receivables 264 198 Other ( 15 ) ( 11 ) Net cash flows used for investing activities ( 242 ) ( 441 ) Cash flows from financing activities: Common stock dividends ( 80 ) ( 180 ) Capital contributions from parent 150 145 Proceeds from issuance of long-term debt — 594 Net change in commercial paper 39 ( 50 ) Other ( 2 ) ( 1 ) Net cash flows from financing activities 107 508 Net increase in cash, cash equivalents and restricted cash 5 175 Cash, cash equivalents and restricted cash at beginning of period 7 29 Cash, cash equivalents and restricted cash at end of period $ 12 $ 204 Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 115 ) ($ 97 ) Income taxes, net (a) $ 79 $ 68 Significant non-cash investing and financing activities: Accrued capital expenditures $ 137 $ 149 Beneficial interest obtained in exchange for securitized accounts receivable $ 95 $ 235 (a) 2026 and 2025 include $ 58 million and $ 73 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers. Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 9 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED) For the Three Months For the Six Months Ended June 30, Ended June 30, 2026 2025 2026 2025 (in millions) Revenues: Electric utility $ 430 $ 433 $ 881 $ 855 Gas utility 39 36 187 158 Other 1 — 2 1 Total revenues 470 469 1,070 1,014 Operating expenses: Electric production fuel and purchased power 87 110 191 218 Electric transmission service 57 51 112 101 Cost of gas sold 15 13 114 86 Other operation and maintenance 87 72 169 137 Depreciation and amortization 98 90 198 183 Taxes other than income taxes 16 15 31 29 Total operating expenses 360 351 815 754 Operating income 110 118 255 260 Other (income) and deductions: Interest expense 49 43 97 86 Allowance for funds used during construction ( 10 ) ( 10 ) ( 21 ) ( 19 ) Other ( 1 ) 3 ( 1 ) 5 Total other (income) and deductions 38 36 75 72 Income before income taxes 72 82 180 188 Income tax benefit ( 6 ) ( 5 ) ( 15 ) ( 10 ) Net income $ 78 $ 87 $ 195 $ 198 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. 10 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) June 30, 2026 December 31, 2025 (in millions, except per share and share amounts) ASSETS Current assets: Cash and cash equivalents $ 12 $ 37 Accounts receivable, less allowance for expected credit losses 247 273 Production fuel, at weighted average cost 35 28 Gas stored underground, at weighted average cost 18 25 Materials and supplies, at weighted average cost 88 81 Regulatory assets 107 96 Prepaid gross receipts tax 55 52 Income taxes receivable 45 1 Other 54 58 Total current assets 661 651 Property, plant and equipment, net 9,729 9,363 Other assets: Regulatory assets 557 562 Deferred charges and other 99 79 Total other assets 656 641 Total assets $ 11,046 $ 10,655 LIABILITIES AND EQUITY Current liabilities: Commercial paper $ 83 $ — Accounts payable 258 197 Accrued interest 45 46 Regulatory liabilities 46 47 Other 105 105 Total current liabilities 537 395 Long-term debt, net 3,671 3,669 Other liabilities: Deferred tax liabilities 881 861 Regulatory liabilities 532 568 Pension and other benefit obligations 68 75 Other 796 712 Total other liabilities 2,277 2,216 Commitments and contingencies ( Note 1 2 ) 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 2,713 2,613 Retained earnings 1,782 1,696 Total Wisconsin Power and Light Company common equity 4,561 4,375 Total liabilities and equity $ 11,046 $ 10,655 Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 11 Table of Contents WISCONSIN POWER AND LIGHT COMPANY CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) For the Six Months Ended June 30, 2026 2025 (in millions) Cash flows from operating activities: Net income $ 195 $ 198 Adjustments to reconcile net income to net cash flows from operating activities: Depreciation and amortization 198 183 Deferred tax benefit and tax credits ( 25 ) ( 43 ) Other 3 ( 4 ) Other changes in assets and liabilities: Accounts receivable 45 ( 33 ) Income taxes receivable ( 44 ) 17 Regulatory liabilities 1 65 Other (a) ( 18 ) ( 46 ) Net cash flows from operating activities 355 337 Cash flows used for investing activities: Construction and acquisition expenditures ( 422 ) ( 348 ) Other ( 29 ) ( 14 ) Net cash flows used for investing activities ( 451 ) ( 362 ) Cash flows from (used for) financing activities: Common stock dividends ( 109 ) ( 119 ) Capital contributions from parent 100 — Net change in commercial paper 83 109 Other ( 3 ) ( 6 ) Net cash flows from (used for) financing activities 71 ( 16 ) Net decrease in cash, cash equivalents and restricted cash ( 25 ) ( 41 ) Cash, cash equivalents and restricted cash at beginning of period 37 51 Cash, cash equivalents and restricted cash at end of period $ 12 $ 10 Supplemental cash flows information: Cash (paid) received during the period for: Interest ($ 97 ) ($ 88 ) Income taxes, net (a) ($ 19 ) $ 8 Significant non-cash investing and financing activities: Accrued capital expenditures $ 129 $ 48 (a) 2026 and 2025 include $ 44 million and $ 24 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers. Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements. 12 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 2025 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 and six months ended June 30, 2026 are not necessarily indicative of results that may be expected for the year ending December 31, 2026. 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 1 (b) Leases - Finance Leases - WPL is currently leasing the Sheboygan Falls Energy Facility from AEF’s Non-utility Generation business. WPL is responsible for the operation of the EGU and has exclusive rights to its output. In the second quarter of 2026, WPL’s rent payments increased following the completion of the Sheboygan Falls Unit 2 advanced gas path project, which increased the efficiency and capacity of the Sheboygan Falls Energy Facility, resulting in a lease modification and remeasurement, which increased both “Property, plant and equipment, net” and “Other liabilities” by approximately $ 70 million on WPL’s balance sheet. For Alliant Energy, the leased Sheboygan Falls Energy Facility is eliminated upon consolidation and therefore is not reflected in Alliant Energy’s balance sheet. NOTE 1 (c) New Accounting Standards - Environmental Credits - In May 2026, the Financial Accounting Standards Board issued an accounting standard that establishes recognition, measurement, presentation and disclosure requirements for environmental credits and environmental credit obligations. The standard requires environmental credits to be evaluated based on their intended use in determining whether the costs of such credits are recognized as assets and how those assets are subsequently measured. The standard also establishes a framework for recognizing and measuring environmental credit obligations and requires expanded annual and interim disclosures regarding environmental credits and environmental credit obligations, including information about the nature, intended use, measurement and settlement of environmental credits and related obligations. Alliant Energy, IPL and WPL currently expect to adopt this standard on January 1, 2028. Upon adoption, the standard is required to be applied retrospectively through a cumulative-effect adjustment to the opening retained earnings balance as of January 1, 2028. Alliant Energy, IPL and WPL are currently evaluating the impact of this standard on their financial condition and results of operations and do not currently anticipate a material increase in environmental credit assets or environmental credit obligations upon adoption. NOTE 2. REGULATORY MATTERS Regulatory Assets and Regulatory Liabilities - Regulatory assets were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 Tax-related $ 1,100 $ 1,089 $ 969 $ 949 $ 131 $ 140 Asset retirement obligations 483 455 328 312 155 143 Pension and OPEB costs 265 274 132 136 133 138 Assets retired early 147 158 140 149 7 9 Derivatives 75 52 24 12 51 40 Non-service pension and OPEB costs 58 57 21 21 37 36 WPL’s Western Wisconsin gas distribution expansion investments 38 39 — — 38 39 Other 145 150 33 37 112 113 $ 2,311 $ 2,274 $ 1,647 $ 1,616 $ 664 $ 658 13 Table of Contents Regulatory liabilities were comprised of the following items (in millions): Alliant Energy IPL WPL June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 Tax-related $ 662 $ 690 $ 286 $ 304 $ 376 $ 386 Cost of removal obligations 340 366 208 217 132 149 Derivatives 35 47 20 26 15 21 Commodity cost recovery 28 13 10 5 18 8 Other 64 85 27 34 37 51 $ 1,129 $ 1,201 $ 551 $ 586 $ 578 $ 615 NOTE 3. 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 2026, IPL amended and extended through March 2029 the purchase commitment from the third party to which it sells receivables. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. Under the amended Receivables Agreement, the limit on cash proceeds fluctuates between $ 5 million and $ 180 million, which IPL may change periodically throughout the year. As of June 30, 2026, the limit on cash proceeds was $ 138 million and IPL had no 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 and six months ended June 30 were as follows (in millions): Three Months Six Months 2026 2025 2026 2025 Maximum outstanding aggregate cash proceeds $ 142 $ 110 $ 142 $ 110 Average outstanding aggregate cash proceeds 105 60 96 84 The attributes of IPL’s receivables sold under the Receivables Agreement were as follows (in millions): June 30, 2026 December 31, 2025 Customer accounts receivable $ 140 $ 147 Unbilled utility revenues 107 104 Receivables sold to third party 247 251 Less: cash proceeds 138 110 Deferred proceeds 109 141 Less: allowance for expected credit losses 14 15 Fair value of deferred proceeds $ 95 $ 126 Outstanding receivables past due $ 19 $ 21 Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and six months ended June 30 were as follows (in millions): Three Months Six Months 2026 2025 2026 2025 Collections $ 482 $ 445 $ 1,096 $ 1,052 Write-offs, net of recoveries 2 2 5 4 Effective July 2026, the limit on cash proceeds under the Receivables Agreement is $ 180 million. 14 Table of Contents NOTE 4. INVESTMENTS Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and six months ended June 30 was as follows (in millions): Three Months Six Months 2026 2025 2026 2025 ATC Holdings ($ 17 ) ($ 14 ) ($ 33 ) ($ 28 ) Non-utility wind farm in Oklahoma ( 4 ) ( 3 ) ( 7 ) ( 4 ) Corporate venture investments (a) ( 22 ) 7 ( 24 ) 11 Other — — ( 1 ) ( 2 ) ($ 43 ) ($ 10 ) ($ 65 ) ($ 23 ) (a) Alliant Energy reports its share of equity earnings from certain corporate venture fund investments on a one-quarter lag. Equity earnings for the three and six months ended June 30, 2026 were primarily driven by increased valuations of certain underlying investments within the venture funds, including an investment in a company that provides onsite power solutions. In June 2026, the onsite power solutions company completed an initial public offering. Due to the one-quarter reporting lag, the financial effects of the initial public offering are expected to be recognized in Alliant Energy’s equity earnings in the third quarter of 2026. NOTE 5. COMMON EQUITY Common Share Activity - A summary of Alliant Energy’s common stock activity was as follows: Shares outstanding, January 1, 2026 257,137,261 At-the-market offering program 929,759 Shareowner Direct Plan 155,122 Equity-based compensation plans 227,746 Convertible debt settlement (Refer to Note 6 for details) 834,811 Shares outstanding, June 30, 2026 259,284,699 At-the-Market Offering Programs - In March 2026, Alliant Energy fully utilized the remaining capacity under its $ 1.3 billion 2025 at-the-market offering program and Alliant Energy filed a new prospectus supplement and executed a related distribution agreement, under which it may sell up to $ 1 billion in aggregate of its common stock through 2029 through an at-the-market offering program that includes an equity forward sales component (the 2026 at-the-market offering program). Alliant Energy expects to use proceeds from the issuance of common stock for general corporate purposes. Alliant Energy entered into forward sale agreements under its 2026 at-the-market offering program with various counterparties who, for the three months ended June 30, 2026, borrowed and sold an aggregate of 6,550,857 shares of Alliant Energy common stock at an aggregate gross sales price of $ 482 million, including approximately $ 4 million in commissions, to the counterparties payable by Alliant Energy when the forward sale agreements are settled. Alliant Energy has not yet received any proceeds from this program and no amounts have been or will be recorded in equity on Alliant Energy’s balance sheets until the forward sale agreements settle. Alliant Energy currently expects to settle the forward sale agreements prior to December 31, 2028 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. As of June 30, 2026, the weighted-average forward price, net of commissions, was $ 72.89 per share and is subject to daily adjustment based on a floating interest rate factor and decreased by other fixed amounts specified in the forward sale agreements. As of June 30, 2026, Alliant Energy could have settled all of its outstanding forward sale agreements under the 2026 at-the-market offering program with physical delivery of 6,912,857 shares of Alliant Energy common stock to the counterparties in exchange for cash of $ 504 million. During the three months ended June 30, 2026, Alliant Energy physically settled its obligations under various forward sale agreements entered into under its 2025 at-the-market offering program with the issuance and delivery of 929,759 shares of common stock at a weighted average forward sale price of $ 63.24 per share, net of commissions. Alliant Energy received net proceeds of $ 59 million, which were recorded in equity on Alliant Energy’s balance sheet. Alliant Energy used the net proceeds for general corporate purposes, which included repayment of commercial paper. Alliant Energy currently expects to settle the remainder of the 2025 at-the-market offering program forward sale agreements in 2026 and 2027 through physical delivery of shares of common stock in exchange for cash proceeds at the then-applicable forward sale price; however, Alliant Energy may elect cash settlement or net share settlement for all or a portion of the obligations under the forward sale agreements. As of June 30, 2026, the weighted-average forward price, net of commissions, of all of the outstanding forward agreements under the 2025 at-the-market offering was $ 66.06 per share and is subject to daily adjustment based on a floating interest rate factor and decreased by other fixed amounts specified in the forward sale agreements. As of June 30, 2026, Alliant Energy could have settled all of its outstanding forward sale agreements under the 2025 at-the-market offering program with physical delivery of 18,668,448 shares of Alliant Energy common stock to the counterparties in exchange for cash of $ 1,233 million. 15 Table of Contents Alliant Energy has concluded that the forward sale agreements meet the derivative scope exception for certain contracts involving an entity’s own equity. Until settlement of the forward sale agreements, Alliant Energy’s EPS dilution resulting from the agreements, if any, is determined using the treasury stock method. Share dilution occurs when the average market price of Alliant Energy stock during the reporting period is higher than the forward sale price as of the end of the reporting period. For the three and six months ended June 30, 2026, 1,741,407 and 46,957 incremental shares were included in the calculation of diluted EPS related to the securities under the forward sale agreements for the 2025 and 2026 at-the-market offering programs, respectively. 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 Trust Equity Three Months Ended June 30, 2026 Beginning balance, March 31, 2026 $ 3 $ 3,101 $ 4,330 $ 2 ($ 14 ) $ 7,422 Net income attributable to Alliant Energy common shareowners 170 170 Common stock dividends ($ 0.535 per share) ( 137 ) ( 137 ) Shareowner Direct Plan issuances 5 5 At-the-market offering program issuances 59 59 Equity-based compensation plans and other 9 9 Other comprehensive income, net of tax 1 1 Ending balance, June 30, 2026 $ 3 $ 3,174 $ 4,363 $ 3 ($ 14 ) $ 7,529 Three Months Ended June 30, 2025 Beginning balance, March 31, 2025 $ 3 $ 3,066 $ 4,037 $ — ($ 13 ) $ 7,093 Net income attributable to Alliant Energy common shareowners 174 174 Common stock dividends ($ 0.5075 per share) ( 131 ) ( 131 ) Shareowner Direct Plan issuances 6 6 Equity-based compensation plans and other 3 3 Ending balance, June 30, 2025 $ 3 $ 3,075 $ 4,080 $ — ($ 13 ) $ 7,145 Alliant Energy Accumulated Shares in Additional Other Deferred Total Common Paid-In Retained Comprehensive Compensation Common Stock Capital Earnings Income Trust Equity Six Months Ended June 30, 2026 Beginning balance, December 31, 2025 $ 3 $ 3,101 $ 4,243 $ 1 ($ 14 ) $ 7,334 Net income attributable to Alliant Energy common shareowners 394 394 Common stock dividends ($ 1.07 per share) ( 274 ) ( 274 ) Shareowner Direct Plan issuances 11 11 At-the-market offering program issuances 59 59 Equity-based compensation plans and other 3 3 Other comprehensive income, net of tax 2 2 Ending balance, June 30, 2026 $ 3 $ 3,174 $ 4,363 $ 3 ($ 14 ) $ 7,529 Six Months Ended June 30, 2025 Beginning balance, December 31, 2024 $ 3 $ 3,060 $ 3,954 $ 1 ($ 14 ) $ 7,004 Net income attributable to Alliant Energy common shareowners 387 387 Common stock dividends ($ 1.015 per share) ( 261 ) ( 261 ) Shareowner Direct Plan issuances 12 12 Equity-based compensation plans and other 3 1 4 Other comprehensive loss, net of tax ( 1 ) ( 1 ) Ending balance, June 30, 2025 $ 3 $ 3,075 $ 4,080 $ — ($ 13 ) $ 7,145 16 Table of Contents IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2026 Beginning balance, March 31, 2026 $ 33 $ 3,622 $ 1,368 $ 5,023 Net income 65 65 Common stock dividends ( 40 ) ( 40 ) Capital contributions from parent 25 25 Ending balance, June 30, 2026 $ 33 $ 3,647 $ 1,393 $ 5,073 Three Months Ended June 30, 2025 Beginning balance, March 31, 2025 $ 33 $ 3,257 $ 1,237 $ 4,527 Net income 98 98 Common stock dividends ( 90 ) ( 90 ) Capital contributions from parent 100 100 Ending balance, June 30, 2025 $ 33 $ 3,357 $ 1,245 $ 4,635 IPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2026 Beginning balance, December 31, 2025 $ 33 $ 3,497 $ 1,314 $ 4,844 Net income 159 159 Common stock dividends ( 80 ) ( 80 ) Capital contributions from parent 150 150 Ending balance, June 30, 2026 $ 33 $ 3,647 $ 1,393 $ 5,073 Six Months Ended June 30, 2025 Beginning balance, December 31, 2024 $ 33 $ 3,212 $ 1,216 $ 4,461 Net income 209 209 Common stock dividends ( 180 ) ( 180 ) Capital contributions from parent 145 145 Ending balance, June 30, 2025 $ 33 $ 3,357 $ 1,245 $ 4,635 WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Three Months Ended June 30, 2026 Beginning balance, March 31, 2026 $ 66 $ 2,638 $ 1,758 $ 4,462 Net income 78 78 Common stock dividends ( 54 ) ( 54 ) Capital contributions from parent 75 75 Ending balance, June 30, 2026 $ 66 $ 2,713 $ 1,782 $ 4,561 Three Months Ended June 30, 2025 Beginning balance, March 31, 2025 $ 66 $ 2,533 $ 1,537 $ 4,136 Net income 87 87 Common stock dividends ( 43 ) ( 43 ) Ending balance, June 30, 2025 $ 66 $ 2,533 $ 1,581 $ 4,180 17 Table of Contents WPL Additional Total Common Paid-In Retained Common Stock Capital Earnings Equity Six Months Ended June 30, 2026 Beginning balance, December 31, 2025 $ 66 $ 2,613 $ 1,696 $ 4,375 Net income 195 195 Common stock dividends ( 109 ) ( 109 ) Capital contributions from parent 100 100 Ending balance, June 30, 2026 $ 66 $ 2,713 $ 1,782 $ 4,561 Six Months Ended June 30, 2025 Beginning balance, December 31, 2024 $ 66 $ 2,533 $ 1,502 $ 4,101 Net income 198 198 Common stock dividends ( 119 ) ( 119 ) Ending balance, June 30, 2025 $ 66 $ 2,533 $ 1,581 $ 4,180 NOTE 6. DEBT NOTE 6(a) Short-term Debt - In March 2026, Alliant Energy, IPL and WPL reallocated credit facility capacity amounts to $ 700 million for Alliant Energy at the parent company level, $ 300 million for IPL and $ 300 million for WPL, within the $ 1.3 billion total commitment. Information regarding Alliant Energy’s, IPL’s and WPL’s commercial paper and borrowings under the single credit facility classified as short-term debt was as follows (dollars in millions): June 30, 2026 Alliant Energy IPL WPL Amount outstanding $ 708 $ 77 $ 83 Weighted average interest rates 3.9 % 3.9 % 3.9 % Available credit facility capacity (a) $ 542 $ 173 $ 217 Alliant Energy IPL WPL Three Months Ended June 30 2026 2025 2026 2025 2026 2025 Maximum amount outstanding (based on daily outstanding balances) $ 732 $ 741 $ 77 $ 141 $ 110 $ 292 Average amount outstanding (based on daily outstanding balances) $ 569 $ 449 $ 12 $ 33 $ 47 $ 225 Weighted average interest rates 3.9 % 4.6 % 3.9 % 4.6 % 3.9 % 4.6 % Six Months Ended June 30 Maximum amount outstanding (based on daily outstanding balances) $ 732 $ 741 $ 103 $ 141 $ 110 $ 292 Average amount outstanding (based on daily outstanding balances) $ 347 $ 495 $ 29 $ 43 $ 24 $ 193 Weighted average interest rates 3.9 % 4.6 % 3.8 % 4.6 % 3.9 % 4.6 % (a) Alliant Energy’s and IPL’s available credit facility capacities reflect outstanding commercial paper classified as both short- and long-term debt at June 30, 2026. In March 2026, Alliant Energy entered into a $ 400 million variable rate ( 4.5 % as of June 30, 2026) term loan credit agreement, which matures in March 2027 and is recorded in “Other short-term borrowings” on Alliant Energy’s balance sheet as of June 30, 2026. Alliant Energy’s 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. The proceeds were used for general corporate purposes. NOTE 6(b) Long-term Debt - As of June 30, 2026, $ 50 million of commercial paper was recorded in “Long-term debt, net” on Alliant Energy’s and IPL’s balance sheets due to the existence of the long-term single credit facility that back-stops this commercial paper balance, along with Alliant Energy’s and IPL’s intent and ability to refinance these balances on a long-term basis. As of June 30, 2026, this commercial paper balance had a 3.9 % interest rate. In January 2026, AEF retired its $ 300 million variable rate term loan. In March 2026, AEF retired its $ 200 million of 1.4 % senior notes. Convertible Senior Notes 2026 Notes - Alliant Energy’s $ 575 million of 3.875 % convertible senior notes issued in March 2023 matured in March 2026. Alliant Energy settled its related conversion obligations to holders by paying the aggregate principal amount outstanding of $ 575 million in cash, and issuing 834,811 shares of Alliant Energy common stock for the excess of its conversion obligation over such principal amount, which was classified as a non-cash financing activity. 18 Table of Contents 2028 Notes - In May 2025, Alliant Energy issued $ 575 million of 3.25 % convertible senior notes (the 2028 Notes), which are senior unsecured obligations. As of June 30, 2026, the conditions allowing holders to convert their 2028 Notes were not met, and the 2028 Notes were classified as “Long-term debt, net” on Alliant Energy’s balance sheet. As of June 30, 2026, the net carrying amount was $ 570 million, with unamortized debt issuance costs of $ 5 million, and the estimated fair value (Level 2) was $ 630 million. For the three and six months ended June 30, 2026, there were no shares of Alliant Energy’s common stock related to the potential conversion of the 2028 Notes included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the 2028 Notes. NOTE 7. REVENUES Disaggregation of revenues from contracts with customers is provided for each reportable segment (IPL and WPL), as well as by customer class within electric and gas sales, as follows (in millions): Alliant Energy IPL WPL Three Months Ended June 30 2026 2025 2026 2025 2026 2025 Electric Utility: Retail - residential $ 309 $ 295 $ 151 $ 142 $ 158 $ 153 Retail - commercial 221 211 143 135 78 76 Retail - industrial 251 240 126 118 125 122 Wholesale 36 49 — 14 36 35 Bulk power and other 44 56 11 9 33 47 Total Electric Utility 861 851 431 418 430 433 Gas Utility: Retail - residential 44 41 23 21 21 20 Retail - commercial 25 20 13 10 12 10 Retail - industrial 3 3 2 2 1 1 Transportation/other 10 12 5 7 5 5 Total Gas Utility 82 76 43 40 39 36 Other Utility: Steam (a) — 9 — 9 — — Other utility 2 2 1 2 1 — Total Other Utility 2 11 1 11 1 — Non-Utility and Other: Travero and other 26 23 — — — — Total Non-Utility and Other 26 23 — — — — Total revenues $ 971 $ 961 $ 475 $ 469 $ 470 $ 469 19 Table of Contents Alliant Energy IPL WPL Six Months Ended June 30 2026 2025 2026 2025 2026 2025 Electric Utility: Retail - residential $ 641 $ 618 $ 311 $ 297 $ 330 $ 321 Retail - commercial 442 425 285 271 157 154 Retail - industrial 491 475 249 236 242 239 Wholesale 71 97 — 28 71 69 Bulk power and other 103 88 22 16 81 72 Total Electric Utility 1,748 1,703 867 848 881 855 Gas Utility: Retail - residential 206 188 99 95 107 93 Retail - commercial 111 94 48 43 63 51 Retail - industrial 9 8 4 4 5 4 Transportation/other 27 26 15 16 12 10 Total Gas Utility 353 316 166 158 187 158 Other Utility: Steam (a) — 19 — 19 — — Other utility 5 6 3 5 2 1 Total Other Utility 5 25 3 24 2 1 Non-Utility and Other: Travero and other 49 44 — — — — Total Non-Utility and Other 49 44 — — — — Total revenues $ 2,155 $ 2,088 $ 1,036 $ 1,030 $ 1,070 $ 1,014 (a) IPL was engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa, which were each under contract through 2025 for taking minimum quantities of annual steam usage. Subsequent to December 31, 2025, IPL exited the steam business. NOTE 8. INCOME TAXES Income Tax Rates - The overall income tax rates shown in the following table were computed by dividing income tax expense (benefit) by income before income taxes. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, net of federal benefits (primarily from state income taxes in Iowa and Wisconsin), production tax credits, investment tax credits, amortization of excess deferred taxes and the effect of rate-making on property-related differences. Also impacting Alliant Energy’s and IPL’s effective income tax rates for the three and six months ended June 30, 2026 were additional tax credits during 2026 from renewable generation and energy storage projects previously placed in service, as well as projects currently expected to be placed in service during 2026. Alliant Energy’s effective income tax rate for the six months ended June 30, 2026 was also impacted by changes in state income tax apportionment. Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2026 2025 2026 2025 2026 2025 2026 2025 2026 2025 2026 2025 Overall income tax rate ( 44 %) ( 33 %) ( 41 %) ( 31 %) ( 103 %) ( 61 %) ( 71 %) ( 58 %) ( 8 %) ( 6 %) ( 8 %) ( 5 %) Deferred Tax Assets and Liabilities - Carryforwards - At June 30, 2026, the carryforwards and expiration dates were estimated as follows (in millions): Range of Expiration Dates Alliant Energy IPL WPL Federal net operating losses Indefinite $ 47 $ 14 $ — State net operating losses 2026-2046 360 7 1 Federal tax credits 2034-2046 700 461 224 20 Table of Contents State Income Tax Apportionment - Deferred tax assets and liabilities are recorded for temporary differences between the tax basis of assets and liabilities and the amounts reported in the financial statements. Deferred taxes are recorded using currently enacted tax rates and estimates of state income tax apportionment. Estimates of state income tax apportionment are supported by historical data and reasonable projections. In the third quarter of 2025, WPL entered into an electric service agreement with a customer who expected to build a data center in WPL’s service territory. In the first quarter of 2026, the customer selected an alternative data center location in IPL’s service territory, and as a result, the electric service agreement with WPL was terminated and subsequently renegotiated and executed with IPL. Accordingly, Alliant Energy currently expects a decrease in Wisconsin state income tax apportionment and an increase in Iowa state income tax apportionment, primarily due to the change in projected electric utility revenues at WPL and IPL. Alliant Energy parent company’s deferred tax assets were remeasured to reflect the change in estimated state income tax apportionment, which resulted in a $ 12 million reduction to income tax expense in Alliant Energy’s income statement and a decrease in deferred tax liabilities on Alliant Energy’s balance sheet in the first quarter of 2026. NOTE 9. BENEFIT PLANS NOTE 9(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 and six months ended June 30 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 Three Months Six Months Three Months Six Months Alliant Energy 2026 2025 2026 2025 2026 2025 2026 2025 Service cost $ 1 $ 1 $ 2 $ 2 $ — $ 1 $ — $ 1 Interest cost 11 12 22 23 2 2 4 4 Expected return on plan assets ( 14 ) ( 14 ) ( 28 ) ( 27 ) ( 1 ) ( 2 ) ( 2 ) ( 3 ) Amortization of actuarial loss 5 5 9 11 — — — — $ 3 $ 4 $ 5 $ 9 $ 1 $ 1 $ 2 $ 2 Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months IPL 2026 2025 2026 2025 2026 2025 2026 2025 Service cost $ 1 $ — $ 1 $ 1 $ — $ — $ — $ — Interest cost 5 5 10 10 1 1 2 2 Expected return on plan assets ( 6 ) ( 6 ) ( 12 ) ( 12 ) ( 1 ) ( 1 ) ( 2 ) ( 2 ) Amortization of actuarial loss 1 2 3 4 — — — — $ 1 $ 1 $ 2 $ 3 $ — $ — $ — $ — Defined Benefit Pension Plans OPEB Plans Three Months Six Months Three Months Six Months WPL 2026 2025 2026 2025 2026 2025 2026 2025 Service cost $ — $ 1 $ — $ 1 $ — $ — $ — $ — Interest cost 5 5 10 10 — — 1 1 Expected return on plan assets ( 6 ) ( 6 ) ( 12 ) ( 12 ) — — — — Amortization of actuarial loss 2 2 4 5 — — — — $ 1 $ 2 $ 2 $ 4 $ — $ — $ 1 $ 1 NOTE 9 (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 and six months ended June 30 was as follows (in millions): Alliant Energy IPL WPL Three Months Six Months Three Months Six Months Three Months Six Months 2026 2025 2026 2025 2026 2025 2026 2025 2026 2025 2026 2025 Compensation expense $ 10 $ 3 $ 16 $ 7 $ 5 $ 2 $ 8 $ 4 $ 4 $ 1 $ 7 $ 3 Income tax benefits — 1 1 2 — — — 1 — — — 1 As of June 30, 2026, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $ 26 million, $ 13 million and $ 12 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years. 21 Table of Contents For the six months ended June 30, 2026, 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 settled 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) 118,637 $ 75.27 Performance shares (net income metric) 118,637 70.06 Restricted stock units 98,600 70.17 For the three and six months ended June 30, 2026, 675,838 shares were included in the calculation of diluted EPS related to the nonvested equity awards. NOTE 10. DERIVATIVE INSTRUMENTS Commodity Derivatives - Notional Amounts - 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 June 30, 2026 Alliant Energy 1,232 2026-2028 24,263 2026-2027 147,110 2026-2032 IPL 726 2026-2028 9,512 2026-2027 71,421 2026-2031 WPL 506 2026-2027 14,751 2026-2027 75,689 2026-2032 December 31, 2025 Alliant Energy 1,682 2026 11,332 2026 140,731 2026-2032 IPL 634 2026 4,482 2026 60,773 2026-2030 WPL 1,048 2026 6,850 2026 79,958 2026-2032 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 June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 Current derivative assets $ 111 $ 49 $ 79 $ 33 $ 32 $ 16 Non-current derivative assets 10 20 6 11 4 9 Current derivative liabilities 38 25 15 9 23 16 Non-current derivative liabilities 33 26 6 2 27 24 During the six months ended June 30, 2026, Alliant Energy’s, IPL’s and WPL’s current derivative assets increased primarily due to new FTRs resulting from the annual FTR auction in the second quarter of 2026 operated by MISO. Based on IPL’s and WPL’s cost recovery mechanisms, the changes in the fair value of derivative liabilities/assets result 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 June 30, 2026 and December 31, 2025, 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. 22 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 June 30, 2026 Derivative assets $ 121 $ 114 $ 85 $ 80 $ 36 $ 34 Derivative liabilities 71 64 21 16 50 48 December 31, 2025 Derivative assets 69 59 44 40 25 19 Derivative liabilities 51 41 11 7 40 34 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. NOTE 11. 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 June 30, 2026 December 31, 2025 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 $ — $ — $ — $ — $ — $ 411 $ 411 $ — $ — $ 411 Commodity derivatives 121 — 18 103 121 69 — 36 33 69 Interest rate derivatives 4 — 4 — 4 1 — 1 — 1 Deferred proceeds 95 — — 95 95 126 — — 126 126 Liabilities: Commodity derivatives 71 — 71 — 71 51 — 50 1 51 Long-term debt (incl. current maturities) 11,010 — 10,650 — 10,650 12,028 — 11,748 — 11,748 IPL June 30, 2026 December 31, 2025 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 $ 85 $ — $ 10 $ 75 $ 85 $ 44 $ — $ 18 $ 26 $ 44 Deferred proceeds 95 — — 95 95 126 — — 126 126 Liabilities: Commodity derivatives 21 — 21 — 21 11 — 10 1 11 Long-term debt 4,732 — 4,456 — 4,456 4,680 — 4,445 — 4,445 WPL June 30, 2026 December 31, 2025 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 $ — $ — $ — $ — $ — $ 25 $ 25 $ — $ — $ 25 Commodity derivatives 36 — 8 28 36 25 — 18 7 25 Liabilities: Commodity derivatives 50 — 50 — 50 40 — 40 — 40 Long-term debt 3,671 — 3,538 — 3,538 3,669 — 3,575 — 3,575 23 Table of Contents 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 June 30 2026 2025 2026 2025 Beginning balance, April 1 $ 16 $ 9 $ 208 $ 86 Total net gains included in changes in net assets (realized/unrealized) 12 10 — — Purchases 91 50 — — Sales ( 3 ) ( 1 ) — — Settlements (a) ( 13 ) ( 12 ) ( 113 ) 149 Ending balance, June 30 $ 103 $ 56 $ 95 $ 235 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 $ 12 $ 10 $ — $ — Alliant Energy Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2026 2025 2026 2025 Beginning balance, January 1 $ 32 $ 25 $ 126 $ 163 Total net gains included in changes in net assets (realized/unrealized) 15 8 — — Purchases 91 50 — — Sales ( 3 ) ( 1 ) — — Settlements (a) ( 32 ) ( 26 ) ( 31 ) 72 Ending balance, June 30 $ 103 $ 56 $ 95 $ 235 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 $ 15 $ 8 $ — $ — IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Three Months Ended June 30 2026 2025 2026 2025 Beginning balance, April 1 $ 13 $ 9 $ 208 $ 86 Total net gains included in changes in net assets (realized/unrealized) 5 6 — — Purchases 69 40 — — Sales ( 2 ) ( 1 ) — — Settlements (a) ( 10 ) ( 10 ) ( 113 ) 149 Ending balance, June 30 $ 75 $ 44 $ 95 $ 235 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 $ 5 $ 6 $ — $ — IPL Commodity Contract Derivative Assets and (Liabilities), net Deferred Proceeds Six Months Ended June 30 2026 2025 2026 2025 Beginning balance, January 1 $ 25 $ 20 $ 126 $ 163 Total net gains included in changes in net assets (realized/unrealized) 7 6 — — Purchases 69 40 — — Sales ( 2 ) ( 1 ) — — Settlements (a) ( 24 ) ( 21 ) ( 31 ) 72 Ending balance, June 30 $ 75 $ 44 $ 95 $ 235 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 $ 7 $ 6 $ — $ — 24 Table of Contents WPL Commodity Contract Derivative Assets and (Liabilities), net Three Months Ended June 30 2026 2025 Beginning balance, April 1 $ 3 $ — Total net gains included in changes in net assets (realized/unrealized) 7 4 Purchases 22 10 Sales ( 1 ) — Settlements ( 3 ) ( 2 ) Ending balance, June 30 $ 28 $ 12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 $ 7 $ 4 WPL Commodity Contract Derivative Assets and (Liabilities), net Six Months Ended June 30 2026 2025 Beginning balance, January 1 $ 7 $ 5 Total net gains included in changes in net assets (realized/unrealized) 8 2 Purchases 22 10 Sales ( 1 ) — Settlements ( 8 ) ( 5 ) Ending balance, June 30 $ 28 $ 12 The amount of total net gains for the period included in changes in net assets attributable to the change in unrealized gains relating to assets and liabilities held at June 30 $ 8 $ 2 (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 FTRs and natural gas commodity contracts categorized as Level 3 was recognized as net derivative assets as follows (in millions): Alliant Energy IPL WPL Excluding FTRs FTRs Excluding FTRs FTRs Excluding FTRs FTRs June 30, 2026 $ 3 $ 100 $ 3 $ 72 $ — $ 28 December 31, 2025 3 29 3 22 — 7 NOTE 12. COMMITMENTS AND CONTINGENCIES NOTE 12(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including expansion of IPL’s gas generation, IPL’s and WPL’s expansion of energy storage and repowering projects at WPL’s Bent Tree Energy Facility. At June 30, 2026, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $ 278 million, $ 171 million and $ 106 million, respectively. Tariff-Related Costs - In February 2026, the Supreme Court ruled that the International Emergency Economic Powers Act (IEEPA) does not provide the Executive Branch of the U.S. government with authority to impose tariffs, and, in March 2026, the Court of International Trade ordered Customs and Border Protection to refund IEEPA tariffs previously collected. Certain third-party suppliers engaged by IPL and WPL act as importers of record and may be eligible for refunds of tariffs previously paid. Alliant Energy, IPL and WPL are currently evaluating the potential recovery of tariff-related costs, which could reduce amounts previously capitalized as part of the construction of generation and energy storage facilities. Due to uncertainty regarding the eligibility, timing and amount of tariff-related cost recoveries, Alliant Energy, IPL and WPL concluded that recovery is not probable and therefore have not recognized any amounts related to potential tariff cost recoveries as of June 30, 2026. 25 Table of Contents NOTE 12 (b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. Purchased power commitments primarily relate to minimum payments associated with electric generating capacity agreements. In addition, there are various purchase commitments associated with other goods and services. At June 30, 2026, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but require payment when electricity is generated by the provider and amounts for future commitments to deliver power to electric customers that do not have current minimum thresholds but will be billed for requirements when power is provided, were as follows (in millions): Alliant Energy IPL WPL Natural gas $ 1,156 $ 484 $ 672 Coal 162 89 73 Purchased power 180 180 — Other (a) 107 55 25 $ 1,605 $ 808 $ 770 (a) Includes individual commitments incurred during the normal course of business that exceeded $ 1 million at June 30, 2026. NOTE 12 (c) Guarantees and Indemnifications - Whiting Petroleum Corporation (Whiting Petroleum) - In 2004, Alliant Energy sold its remaining interest in Whiting Petroleum, an independent oil and gas company. Alliant Energy Resources, LLC, as the successor to a predecessor entity that owned Whiting Petroleum, and a wholly-owned subsidiary of AEF, has guaranteed 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. Whiting Petroleum previously completed bankruptcy proceedings and business combinations, which substantially reduce the likelihood that Alliant Energy will be obligated to make any payments under these guarantees. As of June 30, 2026, the currently known partnership obligations for the abandonment obligations are estimated at $ 92 million, which represents Alliant Energy’s currently estimated maximum exposure under the guarantees. Alliant Energy is not currently aware of, nor does it currently expect to incur in the future, any material liabilities related to these guarantees and therefore has not recognized any material liabilities related to these guarantees as of June 30, 2026 and December 31, 2025. 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 purchased power agreement (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 $ 35 million as of June 30, 2026 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 June 30, 2026 and December 31, 2025. Transfers of Renewable Tax Credits - IPL and WPL have entered into agreements to transfer renewable tax credits from certain wind, solar and energy storage facilities to other corporate taxpayers in exchange for cash. As of June 30, 2026, IPL and WPL provided indemnifications associated with $ 391 million and $ 310 million, respectively, of proceeds for renewable tax credits transferred to other corporate taxpayers 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. Electric Transmission Infrastructure - IPL and WPL have entered into agreements with their respective electric transmission service providers related to the construction of infrastructure necessary for the data centers that are expected to be built in IPL’s and WPL’s service territories by certain of their customers. If these construction projects were to be terminated prior to the infrastructure being placed in service by the electric transmission service providers, then IPL or WPL must reimburse their respective provider for the related costs incurred to-date. As of June 30, 2026, IPL’s and WPL’s related guarantees were approximately $ 184 million and $ 103 million, respectively. Alliant Energy, IPL and WPL are not aware of any material liabilities related to these guarantees that it is probable that they will be obligated to pay and therefore have not recognized any material liabilities related to these guarantees as of June 30, 2026 and December 31, 2025. 26 Table of Contents NOTE 12 (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 June 30, 2026, 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 $ 11 - $ 34 $ 7 - $ 23 $ 4 - $ 11 Current and non-current environmental liabilities $ 13 $ 8 $ 5 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 GHG, including the Clean Air Act. NOTE 12 (e) Collective Bargaining Agreements - At June 30, 2026, employees covered by collective bargaining agreements represented 57 %, 73 % and 85 % of total employees of Alliant Energy, IPL and WPL, respectively. In May 2026, WPL’s collective bargaining agreement with International Brotherhood of Electrical Workers Local 965 expired, representing 29 % and 85 % of total employees of Alliant Energy and WPL, respectively. While the process to renew the agreement is underway and a tentative agreement has been reached, Alliant Energy and WPL are currently unable to predict the outcome. NOTE 13. SEGMENTS OF BUSINESS Alliant Energy’s two reportable segments are IPL and WPL. Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments and reconciliation to consolidated amounts, was as follows (in millions): Utility Total Alliant Reportable Energy Three Months Ended June 30, 2026 IPL WPL Segments Other Consolidated Electric utility revenues $ 431 $ 430 $ 861 N/A $ 861 Gas utility revenues 43 39 82 N/A 82 Other revenues 1 1 2 $ 26 28 Total revenues 475 470 945 26 971 Electric production fuel and purchased power expense 45 87 132 N/A 132 Electric transmission service expense 98 57 155 N/A 155 Cost of gas sold expense 22 15 37 N/A 37 Other operation and maintenance expense 108 87 195 14 209 Other segment items: Depreciation and amortization expense 119 98 217 3 220 Interest expense 57 49 106 37 143 Equity income from unconsolidated investments, net — ( 1 ) ( 1 ) ( 42 ) ( 43 ) Income tax benefit ( 33 ) ( 6 ) ( 39 ) ( 13 ) ( 52 ) Other (a) ( 6 ) 6 — — — Net income 65 78 143 27 170 Total assets (as of June 30, 2026) 12,872 11,046 23,918 1,400 25,318 Investments in equity method subsidiaries (as of June 30, 2026) 4 20 24 713 737 Construction and acquisition expenditures 293 278 571 37 608 27 Table of Contents Utility Total Alliant Three Months Ended June 30, 2025 Reportable Energy IPL WPL Segments Other Consolidated Electric utility revenues $ 418 $ 433 $ 851 N/A $ 851 Gas utility revenues 40 36 76 N/A 76 Other revenues 11 — 11 $ 23 34 Total revenues 469 469 938 23 961 Electric production fuel and purchased power expense 40 110 150 N/A 150 Electric transmission service expense 100 51 151 N/A 151 Cost of gas sold expense 17 13 30 N/A 30 Other operation and maintenance expense 84 72 156 12 168 Other segment items: Depreciation and amortization expense 115 90 205 3 208 Interest expense 52 43 95 29 124 Equity income from unconsolidated investments, net — ( 1 ) ( 1 ) ( 9 ) ( 10 ) Income tax benefit ( 37 ) ( 5 ) ( 42 ) ( 1 ) ( 43 ) Other (a) — 9 9 — 9 Net income (loss) 98 87 185 ( 11 ) 174 Total assets (as of June 30, 2025) 12,180 10,236 22,416 1,334 23,750 Investments in equity method subsidiaries (as of June 30, 2025) 5 18 23 622 645 Construction and acquisition expenditures 252 170 422 61 483 Utility Total Alliant Reportable Energy Six Months Ended June 30, 2026 IPL WPL Segments Other Consolidated Electric utility revenues $ 867 $ 881 $ 1,748 N/A $ 1,748 Gas utility revenues 166 187 353 N/A 353 Other revenues 3 2 5 $ 49 54 Total revenues 1,036 1,070 2,106 49 2,155 Electric production fuel and purchased power expense 110 191 301 N/A 301 Electric transmission service expense 202 112 314 N/A 314 Cost of gas sold expense 96 114 210 N/A 210 Other operation and maintenance expense 195 169 364 26 390 Other segment items: Depreciation and amortization expense 239 198 437 5 442 Interest expense 114 97 211 74 285 Equity income from unconsolidated investments, net — ( 1 ) ( 1 ) ( 64 ) ( 65 ) Income tax benefit ( 66 ) ( 15 ) ( 81 ) ( 33 ) ( 114 ) Other (a) ( 13 ) 10 ( 3 ) 1 ( 2 ) Net income 159 195 354 40 394 Construction and acquisition expenditures 491 422 913 109 1,022 28 Table of Contents Utility Total Alliant Six Months Ended June 30, 2025 Reportable Energy IPL WPL Segments Other Consolidated Electric utility revenues $ 848 $ 855 $ 1,703 N/A $ 1,703 Gas utility revenues 158 158 316 N/A 316 Other revenues 24 1 25 $ 44 69 Total revenues 1,030 1,014 2,044 44 2,088 Electric production fuel and purchased power expense 107 218 325 N/A 325 Electric transmission service expense 207 101 308 N/A 308 Cost of gas sold expense 81 86 167 N/A 167 Other operation and maintenance expense 169 137 306 21 327 Other segment items: Depreciation and amortization expense 230 183 413 7 420 Interest expense 99 86 185 58 243 Equity income from unconsolidated investments, net — ( 1 ) ( 1 ) ( 22 ) ( 23 ) Income tax benefit ( 77 ) ( 10 ) ( 87 ) ( 4 ) ( 91 ) Other (a) 5 16 21 4 25 Net income (loss) 209 198 407 ( 20 ) 387 Construction and acquisition expenditures 628 348 976 89 1,065 (a) Other segment items for each reportable segment include allowance for funds used during construction (AFUDC), taxes other than income taxes, interest income, and other miscellaneous income and deductions. NOTE 14. 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 and six months ended June 30 were as follows (in millions): IPL WPL Three Months Six Months Three Months Six Months 2026 2025 2026 2025 2026 2025 2026 2025 Corporate Services billings $ 67 $ 50 $ 115 $ 97 $ 66 $ 48 $ 113 $ 95 Sales credited 4 1 11 2 25 40 65 62 Purchases billed 110 107 206 200 23 16 34 35 Net intercompany payables to Corporate Services were as follows (in millions): IPL WPL June 30, 2026 December 31, 2025 June 30, 2026 December 31, 2025 Net payables to Corporate Services $ 145 $ 135 $ 85 $ 84 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 and six months ended June 30 were as follows (in millions): Three Months Six Months 2026 2025 2026 2025 ATC billings to WPL $ 44 $ 38 $ 91 $ 76 WPL billings to ATC 7 5 16 11 WPL owed ATC net amounts of $ 12 million as of June 30, 2026 and $ 10 million as of December 31, 2025. 29 Table of Contents 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 2025 Form 10-K . Unless otherwise noted, all “per share” references in MDA refer to earnings per diluted share. 2026 HIGHLIGHTS Key highlights since the filing of the 2025 Form 10-K include the following: Customer Investments: • In March 2026, the IUC approved advance rate-making principles for IPL for up to 1,000 MW of new wind generation in Iowa. The rate-making principles approved include a fixed cost cap of $3,020/kilowatt, including AFUDC and transmission costs, among other costs. IPL’s return on common equity will be the same as other assets without advance rate-making principles for the purposes of setting future rates and IPL’s blended return on common equity, which will be updated each year, will be used for IPL’s retail electric earnings sharing mechanism calculation. • In March 2026, WPL filed a certificate of authority application with the PSCW for approval to construct, own and install equipment that will maintain and increase the capacity and efficiency of its Riverside Energy Center. A decision from the PSCW is currently expected in the second quarter of 2027. • In April 2026, IPL filed a certificate of public convenience, use and necessity (GCU Certificate) application with the IUC for approval to construct, own and operate an approximately 720 MW simple-cycle natural gas-fired EGU in Linn County, Iowa. A decision from the IUC is currently expected in the first quarter of 2027. • In May 2026, IPL filed an application for amendment to its GCU Certificate with the IUC for approval to construct, own and operate up to an additional 125 MW of energy storage at the site of its Whispering Willow - North wind farm. The application seeks to increase the energy storage capacity at the site from the 75 MW previously approved to approximately 200 MW. A decision from the IUC is currently expected in the fourth quarter of 2026. • In June 2026, the Neenah Unit 2 and Sheboygan Falls Unit 2 advanced gas path projects were completed, which increased the efficiency and capacity at each of these EGUs. • In July 2026, IPL filed a GCU Certificate application with the IUC for approval to construct, own and operate an approximately 1,200 MW simple-cycle natural gas-fired EGU near the site of its Emery Generating Station, known as the Riverhawk Energy Center. A decision from the IUC is currently expected in the second quarter of 2027. • In July 2026, the PSCW issued an order authorizing WPL to construct, own and operate the Bent Tree North EGU, an approximately 153 MW wind farm. Rate Matters: Large Load Tariff – In connection with its June 2026 approval of an individual customer rate (ICR), the PSCW directed WPL to file a large load tariff applicable to all customers with demand requirements of 100 MW or greater. The tariff must be filed before or concurrently with any future request for approval of an electric service agreement with a customer of 100 MW or greater of demand requirements. The large load tariff must specify the rates, terms and conditions applicable to customers meeting the applicable threshold and describe the standards and protections WPL will apply when evaluating electric service agreements with large load growth customers. In addition, customers served under approved ICRs must be treated as a separate customer class for purposes of future cost-of-service studies in WPL’s next retail electric rate review. The requirement to file a large load tariff did not affect the PSCW’s June 2026 approval of the ICR. Refer to “ Growing Customer Demand ” for additional information regarding the approved ICR. Growing Customer Demand: • In April 2026, IPL entered into an electric service agreement with a customer, who currently expects to build a data center in IPL’s service territory. This electric service agreement includes contracted peak demand of approximately 370 MW. The actual timing and amount of increases in IPL’s load are subject to various factors, including interconnections and actual customer demand, and any executed or future agreements with customers are not expected to result in immediate increases in load. • In June 2026, the PSCW approved an ICR for a customer who is constructing a data center in WPL’s service territory, subject to certain conditions, including the recognition of demand revenue received prior to WPL’s next retail electric rate review through WPL’s retail electric fuel cost recovery mechanism. Refer to “ Rate Matters ” for additional information regarding the large load tariff requirements established by the PSCW in connection with its approval of the ICR. Environmental Matters: Coal Combustion Residuals (CCR) Rule - In April 2026, the EPA proposed a rule that would significantly reduce the scope of the CCR Rule, which is currently anticipated to be finalized by the end of 2026. Alliant Energy, IPL and WPL continue to evaluate the revised CCR Rule and are unable to predict with certainty the future outcome or impact of these updates, including resolution of ongoing litigation. 30 Table of Contents Effluent Limitation Guidelines and Standards (ELGs) - In May 2026, the EPA proposed changes to the 2024 ELG Rule, which are currently anticipated to be finalized by the end of 2026. The proposed rule would revise discharge limits for specific categories of wastewater from certain existing steam EGUs. If finalized, the revised limitations would be implemented in the wastewater discharge permits issued by state agencies to affected facilities. Alliant Energy, IPL and WPL continue to evaluate the revised 2024 ELG Rule and are unable to predict with certainty the future outcome or impact of these updates, including resolution of ongoing or potential litigation. Legislative Matters: • In April 2026, the State of Wisconsin enacted 2025 Wisconsin Act 193, which requires utilities to include their capacity costs and revenues in their annual fuel cost plans. The most significant provisions of the legislation for Alliant Energy and WPL are the requirement that fuel cost calculations in approved fuel cost plans account for both the cost of purchasing capacity and the revenue generated from selling it. The legislation applies to fuel cost plans filed on or after January 1, 2027. RESULTS OF OPERATIONS Financial Results Overview - The table below includes diluted 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 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 diluted EPS attributable to Alliant Energy common shareowners for the three months ended June 30 were as follows (dollars in millions, except per share amounts): 2026 2025 Income (Loss) EPS Income (Loss) EPS Utilities and Corporate Services $148 $0.57 $190 $0.74 ATC Holdings 12 0.05 10 0.04 Non-utility and Parent 10 0.03 (26) (0.10) Alliant Energy Consolidated $170 $0.65 $174 $0.68 Alliant Energy’s Utilities and Corporate Services net income decreased by $42 million for the three-month period, primarily due to higher other operation and maintenance, financing and depreciation expenses, the timing of income taxes and estimated temperature impacts on retail electric and gas sales. These items were partially offset by higher revenue requirements from IPL’s and WPL’s capital investments. Alliant Energy’s Non-utility and Parent net income increased $36 million for the three-month period, primarily due to higher equity earnings from corporate venture investments and the timing of income taxes, partially offset by higher financing expense. 31 Table of Contents Net Income Variances - The following items contribute d to increased (decreased) net income for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL Revenues: Changes in electric utility (Refer to details below ) $10 $13 ($3) $45 $19 $26 Changes in gas utility (Refer to details below ) 6 3 3 37 8 29 Changes in other utility (Refer to Note 7 for details) (9) (10) 1 (20) (21) 1 Changes in non-utility 3 — — 5 — — Changes in total revenues 10 6 1 67 6 56 Operating expenses: Changes in electric production fuel and purchased power (Refer to details below ) 18 (5) 23 24 (3) 27 Changes in electric transmission service (Refer to details below) (4) 2 (6) (6) 5 (11) Changes in cost of gas sold (Refer to details below ) (7) (5) (2) (43) (15) (28) Changes in other operation and maintenance (Refer to details below ) (41) (24) (15) (63) (26) (32) Changes in depreciation and amortization (Higher primarily due to energy storage placed in service in 2025) (12) (4) (8) (22) (9) (15) Changes in taxes other than income taxes (2) (1) (1) (2) (1) (2) Changes in total operating expenses (48) (37) (9) (112) (49) (61) Changes in operating income (38) (31) (8) (45) (43) (5) Other income and deductions: Changes in interest expense (Higher primarily due to financings completed in 2025) (19) (5) (6) (42) (15) (11) Changes in equity income from unconsolidated investments, net (Refer to Note 4 for details) 33 — — 42 — — Changes in allowance for funds used during construction (Primarily due to changes in levels of construction work in progress balances related to energy storage and gas generation) 8 8 — 20 18 2 Changes in Other 3 (1) 4 9 1 6 Changes in total other income and deductions 25 2 (2) 29 4 (3) Changes in income before income taxes (13) (29) (10) (16) (39) (8) Changes in income taxes (Refer to Note 8 for details) 9 (4) 1 23 (11) 5 Changes in net income ($4) ($33) ($9) $7 ($50) ($3) Electric and Gas Revenues and Sales Summary - Electric and gas revenues (in millions), and MWh and Dth sales (in thousands), for the three and six months ended June 30 were as follows: Alliant Energy Electric Gas Revenues MWhs Sold Revenues Dths Sold 2026 2025 2026 2025 2026 2025 2026 2025 Three Months Retail $781 $746 5,987 5,926 $72 $64 5,814 6,114 Sales for resale: Wholesale 36 49 497 651 N/A N/A N/A N/A Bulk power and other 31 43 1,049 1,176 N/A N/A N/A N/A Transportation/Other 13 13 13 14 10 12 29,955 27,159 $861 $851 7,546 7,767 $82 $76 35,769 33,273 Six Months Retail $1,574 $1,518 12,124 12,100 $326 $290 28,299 29,936 Sales for resale: Wholesale 71 97 1,008 1,342 N/A N/A N/A N/A Bulk power and other 83 69 2,675 2,554 N/A N/A N/A N/A Transportation/Other 20 19 26 28 27 26 62,769 58,165 $1,748 $1,703 15,833 16,024 $353 $316 91,068 88,101 32 Table of Contents IPL Electric Gas Revenues MWhs Sold Revenues Dths Sold 2026 2025 2026 2025 2026 2025 2026 2025 Three Months Retail $420 $395 3,275 3,286 $38 $33 2,602 2,667 Sales for resale: Wholesale — 14 2 161 N/A N/A N/A N/A Bulk power and other 3 1 448 301 N/A N/A N/A N/A Transportation/Other 8 8 7 8 5 7 10,264 10,295 $431 $418 3,732 3,756 $43 $40 12,866 12,962 Six Months Retail $845 $804 6,670 6,724 $151 $142 13,442 14,439 Sales for resale: Wholesale — 28 5 343 N/A N/A N/A N/A Bulk power and other 11 2 992 697 N/A N/A N/A N/A Transportation/Other 11 14 14 16 15 16 22,189 22,366 $867 $848 7,681 7,780 $166 $158 35,631 36,805 WPL Electric Gas Revenues MWhs Sold Revenues Dths Sold 2026 2025 2026 2025 2026 2025 2026 2025 Three Months Retail $361 $351 2,712 2,640 $34 $31 3,212 3,447 Sales for resale: Wholesale 36 35 495 490 N/A N/A N/A N/A Bulk power and other 28 42 601 875 N/A N/A N/A N/A Transportation/Other 5 5 6 6 5 5 19,691 16,864 $430 $433 3,814 4,011 $39 $36 22,903 20,311 Six Months Retail $729 $714 5,454 5,376 $175 $148 14,857 15,497 Sales for resale: Wholesale 71 69 1,003 999 N/A N/A N/A N/A Bulk power and other 72 67 1,683 1,857 N/A N/A N/A N/A Transportation/Other 9 5 12 12 12 10 40,580 35,799 $881 $855 8,152 8,244 $187 $158 55,437 51,296 Sales Trends and Temperatures - All iant Energy’s retail electric sa les volumes increased 1% and remained unchanged for the three and six months ended June 30, 2026, respectively, compared to the same periods in 2025, primarily due to higher sales to commercial and industrial customers at WPL, partially offset by changes in temperatures. Alliant Energy’s retail gas sales volumes decreased 5% and 5% for the three and six months ended June 30, 2026, respectively, compared to the same periods in 2025, primarily due to changes in temperatures. Estimated increases (decreases) to operating income from the impacts of temperatures for the three and six months ended June 30 were as follows (in millions): Electric Gas Three Months Six Months Three Months Six Months 2026 2025 Change 2026 2025 Change 2026 2025 Change 2026 2025 Change IPL ($3) $4 ($7) ($9) $— ($9) ($1) ($1) $— ($5) ($3) ($2) WPL (6) 3 (9) (9) — (9) (1) — (1) (3) (1) (2) Total Alliant Energy ($9) $7 ($16) ($18) $— ($18) ($2) ($1) ($1) ($8) ($4) ($4) Electric Sales for Resale - Alliant Energy’s and IPL’s wholesale sales volumes decreased for the three and six months ended June 30, 2026, respectively, compared to the same periods in 2025, primarily due to the expiration of IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative in 2025. 33 Table of Contents 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 contribute d to increased (decreased) electri c utility revenues for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL Higher revenue requirements (a) $26 $— $26 $53 $— $53 Higher revenues at IPL due to credits on customers’ bills through the tax benefit rider in 2025 (partially offset by changes in wholesale revenues and income taxes) 16 16 — 34 34 — Higher (lower) sales for resale bulk power and other revenues (b) (12) 2 (14) 14 9 5 Higher revenues at IPL related to changes in recovery amounts for energy efficiency costs through the energy efficiency rider (mostly offset by changes in energy efficiency expense) 4 4 — 10 10 — Lower wholesale revenues at IPL primarily due to lower sales from the expiration of IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative in 2025 (14) (14) — (28) (28) — Changes in WPL refunds/collections of previous over-/under-collection of retail electric fuel-related costs (offset in electric production fuel and purchased power expenses) (12) — (12) (25) — (25) Estimated changes in sales volumes caused by temperatures (16) (7) (9) (18) (9) (9) Higher (lower) revenues primarily due to changes in retail electric fuel-related costs (Refer to Electric Production Fuel and Purchased Power Expenses Variances below) (a) 3 4 (1) (12) — (12) Lower revenues at IPL due to credits on customers’ bills related to production tax credits through its fuel-related cost recovery mechanism (offset by changes in income taxes) (9) (9) — (10) (10) — Other (primarily due to higher temperature-normalized retail sales) 24 17 7 27 13 14 $10 $13 ($3) $45 $19 $26 (a) In December 2025, the PSCW issued an order authorizing an annual base rate increase of $69 million for WPL’s retail electric customers, covering the 2026 forward-looking Test Period, which reflects revenue requirement impacts of increasing electric rate base, including wind refurbishment projects, energy storage, existing natural gas-fired EGU improvements and electric distribution investments and lower forecasted fuel-related expenses. (b) Sales for resale bulk power and other revenues decreased for the three months ended June 30, 2026 compared to the same period in 2025, primarily due to lower volumes and lower prices for electricity sold by WPL to MISO wholesale energy markets. Sales for resale bulk power and other revenues increased for the six months ended June 30, 2026 compared to the same period in 2025, primarily due to higher volumes and higher prices for electricity sold by IPL and WPL to MISO wholesale energy markets. These changes were largely offset by changes in fuel-related costs. 34 Table of Contents Gas Utility Revenue Variances - The following items contribute d to increased (decreased) gas utility revenues for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL Higher revenues due to changes in gas costs (Refer to Cost of Gas Sold Expense Variances below) $8 $6 $2 $43 $15 $28 Higher revenue requirements (a) 1 — 1 3 — 3 Estimated changes in sales volumes caused by temperatures (1) — (1) (4) (2) (2) Lower revenues at IPL related to changes in recovery amounts for energy efficiency costs through the energy efficiency rider (mostly offset by changes in energy efficiency expense) — — — (3) (3) — Other (2) (3) 1 (2) (2) — $6 $3 $3 $37 $8 $29 (a) In December 2025, the PSCW issued an order authorizing an annual base rate increase of $7 million for WPL’s retail gas customers, covering the 2026 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 contrib uted to (increased) decreased ele ctric production fuel and purchased power expenses for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL (Higher) lower purchased power expense (a) $11 $15 ($4) $28 $29 ($1) Changes in WPL refunds/collections of previous over-/under-collection of retail electric fuel-related costs (offset in electric utility revenue) 12 — 12 25 — 25 (Higher) lower electric production fuel costs (b) 13 4 9 (22) (7) (15) Changes in regulatory recovery of retail electric fuel-related costs (17) (25) 8 (4) (24) 20 Other (1) 1 (2) (3) (1) (2) $18 ($5) $23 $24 ($3) $27 (a) Purchased power expense decreased for the three and six months ended June 30, 2026 compared to the same periods in 2025, primarily due to lower prices for electricity purchased and lower volumes purchased at IPL. (b) Electric production fuel costs decreased for the three months ended June 30, 2026 compared to the same period in 2025, primarily due to lower natural gas volumes at IPL and WPL due to lower dispatch of natural gas-fired EGUs and lower coal volumes at WPL due to lower dispatch of coal-fired EGUs, partially offset by higher natural gas prices. Electric production fuel costs increased for the six months ended June 30, 2026 compared to the same period in 2025, primarily due to higher natural gas prices and higher natural gas volumes at WPL due to higher dispatch of natural gas-fired EGUs, partially offset by lower coal volumes at WPL due to lower dispatch of coal-fired EGUs and lower natural gas volumes at IPL due to lower dispatch of natural gas-fired EGUs. 35 Table of Contents Electric Transmission Service Expense Variances - The following items contributed to (increased) decreased elec tric transmission service expense for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL Changes in regulatory recovery for the difference between actual electric transmission service costs and those costs used to determine rates $11 $11 $— $17 $17 $— Other (primarily due to changes in transmission service costs provided by third parties) (15) (9) (6) (23) (12) (11) ($4) $2 ($6) ($6) $5 ($11) Cost of Gas Sold Expense Variances - The following items contribut ed to (increased) decreased cos t of gas sold expense for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL Changes in retail gas volumes and natural gas prices $— ($1) $1 ($45) ($22) ($23) Changes in the regulatory recovery of gas costs (8) (5) (3) 3 7 (4) Other 1 1 — (1) — (1) ($7) ($5) ($2) ($43) ($15) ($28) Other Operation and Maintenance Expenses Variances - The following items contribu ted to (increased) decreased ot her operation and maintenance expenses for the three and six months ended June 30, 2026 compared to the same periods in 2025 (in millions): Three Months Six Months Alliant Energy IPL WPL Alliant Energy IPL WPL Higher incentive compensation expense ($16) ($9) ($7) ($20) ($11) ($9) Higher generation and energy delivery expenses (2) (2) — (19) (8) (11) Higher energy efficiency expense at IPL (mostly offset by higher revenues) (5) (5) — (9) (9) — Other (18) (8) (8) (15) 2 (12) ($41) ($24) ($15) ($63) ($26) ($32) LIQUIDITY AND CAPITAL RESOURCES The liquidity and capital resources summary included in the 2025 Form 10-K has not changed materially, except as described below. Liquidity Position - At June 30, 2026, Alliant Energy had $25 million of cash and cash equivalents, $542 million ($152 million at the parent company, $173 million at IPL and $217 million at WPL) of available capacity under the single revolving credit facility and no available capacity at IPL under its sales of accounts receivable program. Capital Structure - The following table shows financial capital structures as of June 30, 2026, as well as an adjusted capitalization structure that Alliant Energy believes is consistent with how a majority of the rating agencies currently view its junior subordinated notes (in millions): Alliant Energy IPL WPL Actual Adjusted (a) Actual Actual Common equity $7,529 $7,892 $5,073 $4,561 Long-term debt (including current maturities) 11,010 10,647 4,732 3,671 Short-term debt 1,108 1,108 77 83 Total capitalization $19,647 $19,647 $9,882 $8,315 Total debt $12,118 $11,755 $4,809 $3,754 Ratio of debt to total capitalization 62 % 60 % 49 % 45 % (a) The long-term debt component of Alliant Energy’s financial capital structure includes junior subordinated notes classified as “Long-term debt, net” on Alliant Energy’s balance sheet. The adjusted presentation attributes 50% of the junior subordinated notes to common equity and 50% to long-term debt, to align with the debt-to-capital ratio used by the majority of rating agencies. The non-GAAP adjusted presentation reflecting this treatment is useful and relevant to investors in understanding how management and the rating agencies evaluate Alliant Energy’s capital structure. 36 Table of Contents Cash Flows - Selected information from the cash flows statements was as follows (in millions): Alliant Energy IPL WPL 2026 2025 2026 2025 2026 2025 Cash, cash equivalents and restricted cash, January 1 $556 $81 $7 $29 $37 $51 Cash flows from (used for): Operating activities 481 492 140 108 355 337 Investing activities (795) (894) (242) (441) (451) (362) Financing activities (217) 650 107 508 71 (16) Net increase (decrease) (531) 248 5 175 (25) (41) Cash, cash equivalents and restricted cash, June 30 $25 $329 $12 $204 $12 $10 Operating Activities - The following items contributed t o increased (decreased) ope rating activity cash flows for the six months ended June 30, 2026 compared to the same period in 2025 (in millions): Alliant Energy IPL WPL Changes in interest payments ($54) ($18) ($9) Timing of WPL’s fuel-related cost recoveries from retail electric customers (45) — (45) Lower wholesale revenues at IPL primarily due to lower sales from the expiration of IPL’s wholesale power agreement with Southern Minnesota Energy Cooperative in 2025 (28) (28) — Decreased collections from IPL’s and WPL’s retail customers caused by temperature impacts on electric and gas sales (22) (11) (11) Timing of intercompany payments and receipts — 2 27 Higher collections from WPL’s retail electric and gas base rate increases 56 — 56 Changes in the sales of accounts receivable at IPL 37 37 — Higher collections from IPL’s retail customers due to credits on customers’ bills related to the tax benefit rider in 2025 34 34 — Changes in income taxes paid/received (a) 5 11 (27) Other (primarily due to other changes in working capital) 6 5 27 ($11) $32 $18 (a) Refer to the cash flows statements for details of renewable tax credits transferred to other corporate taxpayers during the six months ended June 30, 2026 and 2025. Investing Activities - The following items contributed to increased (decreased) inv esting activity cash flows for the six months ended June 30, 2026 compared to the same period in 2025 (in millions): Alliant Energy IPL WPL Changes in the amount of cash receipts on sold receivables $66 $66 $— Lower (higher) utility construction and acquisition expenditures (a) 63 137 (74) Higher non-utility construction and acquisition expenditures (20) — — Other (10) (4) (15) $99 $199 ($89) (a) Largely due to lower expenditures for IPL’s energy storage and refurbishment of existing wind farms, partially offset by higher expenditures for WPL’s refurbishment of existing wind farms. Financing Activities - The following items contributed to increased (decreased) fin ancing activity cash flows for the six months ended June 30, 2026 compared to the same period in 2025 (in millions): Alliant Energy IPL WPL Lower net proceeds from issuance of long-term debt ($1,162) ($594) $— Higher payments to retire long-term debt (1,075) — — Changes in common stock dividends (13) 100 10 Higher capital contributions from IPL’s and WPL’s parent company, Alliant Energy — 5 100 Net changes in the amount of commercial paper outstanding 936 89 (26) Higher proceeds from issuance of other short-term borrowings 400 — — Higher net proceeds from common stock issuances 58 — — Other (11) (1) 3 ($867) ($401) $87 37 Table of Contents Common Stock Issuances - Refer to Note 5 for discussion of common stock issuances by Alliant Energy in 2026 and Alliant Energy’s at-the-market offering programs. Short-term Debt - Refer to Note 6(a) for discussion of Alliant Energy’s term loan credit agreement entered into in 2026. Long-term Debt - Refer to Note 6(b) for discussion of issuances and/or retirements of long-term debt by Alliant Energy, AEF and IPL in 2026. Impact of Credit Ratings on Liquidity and Collateral Obligations - Ratings Triggers - In March 2026, Standard & Poor’s Ratings Services changed certain IPL credit ratings, which are not expected to have a material impact on Alliant Energy’s and IPL’s liquidity or collateral obligations. Alliant Energy’s, IPL’s and WPL’s current credit ratings and outlooks are as follows: Standard & Poor’s Ratings Services Alliant Energy: Corporate/issuer BBB+ Commercial paper A-2 Senior unsecured long-term debt BBB Outlook Stable IPL: Corporate/issuer A- Commercial paper A-2 Senior unsecured long-term debt A- Outlook Stable WPL: Corporate/issuer A- Commercial paper A-2 Senior unsecured long-term debt A- Outlook Stable 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 2025 Form 10-K and has not changed materially from the items reported in the 2025 Form 10-K , except for the items described in Notes 3 , 6 and 12 . ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK Quantitative and Qualitative Disclosures About Market Risk are reported in the 2025 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 June 30, 2026 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 June 30, 2026. There was no change in Alliant Energy’s, IPL’s and WPL’s internal control over financial reporting that occurred during the quarter ended June 30, 2026 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. 38 Table of Contents ITEM 1A. RISK FACTORS The risk factors described in Item 1A in the 2025 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 June 30, 2026 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) April 1 through April 30 5,201 $73.10 — N/A May 1 through May 31 2,639 70.91 — N/A June 1 through June 30 7 72.94 — N/A 7,847 72.36 — (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 During the quarter ended June 30, 2026, 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 . Amended and Restated Bylaws On July 29, 2026, the Board of Directors (the “Board”) of Alliant Energy Corporation (the “Company”) approved an amendment and restatement, effective July 31, 2026 (the “Amendment and Restatement”), of the Amended and Restated Bylaws of the Company, dated November 8, 2022 (the “Bylaws”). The Amendment and Restatement amends Section 4.4 of the Bylaws to remove provisions relating to (i) the age following which directors are not eligible to be re-elected to the Board and (ii) the process by which a director must provide notice and tender a resignation to the Board following a change in employment, with such topics instead addressed within the Company’s Corporate Governance Guidelines, which are available on the Company’s investor website. The Amendment and Restatement also amends Section 6.1 of the Bylaws to update the officers required to be elected by the Board to a specified list of officers identified in the Bylaws, together with any executive officers of the Company as defined by the rules and regulations of the Securities and Exchange Commission. Additionally, the Amendment and Restatement contains amendments to Section 6.3 and 6.6, in order to conform to the changes in Section 6.1. The foregoing description of the Amendment and Restatement does not purport to be complete and is qualified in its entirety by reference to the full text of the Amended and Restated Bylaws, effective July 31, 2026, which is filed as Exhibit 3.1 to this Quarterly Report on Form 10-Q and is incorporated herein by reference. 39 Table of Contents ITEM 6. EXHIBITS The following Exhibits are filed herewith or incorporated herein by reference. Exhibit Number Description 3.1 Amended and Restated Bylaws of Alliant Energy, effective July 31, 2026 3.2 Amended and Restated Bylaws of IPL, effective July 31, 2026 3.3 Amended and Restated Bylaws of WPL, effective July 31, 2026 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 t he 31st day of July 2026. ALLIANT ENERGY CORPORATION Registrant By: /s/ Dylan M. Syse Chief Accounting Officer and Controller Dylan M. Syse (Principal Accounting Officer and Authorized Signatory) INTERSTATE POWER AND LIGHT COMPANY Registrant By: /s/ Dylan M. Syse Chief Accounting Officer and Controller Dylan M. Syse (Principal Accounting Officer and Authorized Signatory) WISCONSIN POWER AND LIGHT COMPANY Registrant By: /s/ Dylan M. Syse Chief Accounting Officer and Controller Dylan M. Syse (Principal Accounting Officer and Authorized Signatory) 40