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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 September 30, 2025

☐ 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 CORPORATION

(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 COMPANY

(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 COMPANY

(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 September 30, 2025:

Alliant Energy Corporation, Common Stock, $0.01 par value, 257,053,689 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			3
Item 1. Condensed Consolidated Financial Statements (Unaudited)			3
Alliant Energy Corporation			3
Interstate Power and Light Company			6
Wisconsin Power and Light Company			9
Combined Notes to Condensed Consolidated Financial Statements			12
1. Summary of Significant Accounting Policies			12
2. Regulatory Matters			12
3. Property, Plant and Equipment			13
4 . Receivables			13
5 . Investments			14
6 . Common Equity			14
7 . Debt			16
8 . Revenues			18
9 . Income Taxes			19
10 . Benefit Plans			20

1 1 . Derivative Instruments			21
1 2 . Fair Value Measurements			22
1 3 . Commitments and Contingencies			24
1 4 . Segments of Business			26
1 5 . Related Parties			27
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of Operations			28
Item 3. Quantitative and Qualitative Disclosures About Market Risk			39
Item 4. Controls and Procedures			39
Part II. Other Information			39
Item 1. Legal Proceedings			39
Item 1A. Risk Factors			39
Item 2. Unregistered Sales of Equity Securities and Use of Proceeds			40
Item 5. Other Information			40
Item 6. Exhibits			40
Signatures			41

DEFINITIONS

The following abbreviations or acronyms used in this report are defined below:


Abbreviation or Acronym	Definition	Abbreviation or Acronym	Definition
2024 Form 10-K	Combined Annual Report on Form 10-K filed by Alliant Energy, IPL and WPL for the year ended Dec. 31, 2024	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	U.S.	United States of America
FTR	Financial transmission right	West Riverside	West Riverside Energy Center and Solar Facility
GAAP	U.S. generally accepted accounting principles	WPL	Wisconsin Power and Light Company

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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 generation projects including such costs that are incurred prior to regulatory approval or 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;

•the impact of IPL’s retail electric base rate moratorium;

•the ability to obtain regulatory approval for construction projects with acceptable conditions;

•the ability to complete construction of generation and energy storage projects by planned in-service dates and within the cost targets set by regulators due to cost increases of and access to materials, equipment and commodities, which could result from tariffs, including previously exempted tariffs related to solar project materials and equipment from certain countries, duties or other assessments, inflation, labor issues or supply shortages, the ability to successfully resolve warranty issues or contract disputes and the ability to obtain adequate generator interconnection agreements to connect the new projects to MISO 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, including alternative electric suppliers and potential policy changes that may enable large customers to source behind-the-meter generation directly from third parties, 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 provide sufficient generation and the ability of ITC Midwest LLC 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 or permitting actions, public opposition or other factors, as well as the resulting higher system load demand by expected levels and timeframes;

•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 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 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;

•the impacts of changes in the tax code, including tax rates, minimum tax rates, adjustments made to deferred tax assets and liabilities, and changes impacting the availability of and ability to transfer renewable tax credits, 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 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;


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•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 resource adequacy process establishing capacity planning reserve margin and capacity accreditation requirements that may impact how and when new and existing generating facilities, including IPL’s and WPL’s additional solar generation, may be accredited with energy capacity, and may require IPL and WPL to adjust their current resource plans, to add resources to meet the requirements of MISO’s process, or procure capacity in the market whereby such costs might not be recovered in rates;

•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 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;

•changes in technology that alter the channels through which customers buy or utilize Alliant Energy’s, IPL’s or WPL’s products and services;

•impacts on equity income from unconsolidated investments from changes in valuations of the assets held, as well as potential changes to ATC’s authorized return on equity;

•impacts of IPL’s future tax benefits from Iowa rate-making practices, including deductions for repairs expenditures 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 2024 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.


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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 Nine Months
	Ended September 30,		Ended September 30,
	2025	2024	2025	2024
	(in millions, except per share amounts)
Revenues:
Electric utility	$1,124	$999	$2,828	$2,579
Gas utility	51	49	366	322
Other utility	12	12	37	36
Non-utility	23	21	67	68
Total revenues	1,210	1,081	3,298	3,005
Operating expenses:
Electric production fuel and purchased power	239	192	564	493
Electric transmission service	166	165	474	464
Cost of gas sold	12	13	180	152
Other operation and maintenance:
Asset valuation charge for IPL’s Lansing Generating Station	—	—	—	60
Other	204	174	530	510
Depreciation and amortization	211	195	631	571
Taxes other than income taxes	29	29	91	90
Total operating expenses	861	768	2,470	2,340
Operating income	349	313	828	665
Other (income) and deductions:
Interest expense	128	114	372	329
Equity income from unconsolidated investments, net	(18)	(14)	(41)	(44)
Allowance for funds used during construction	(24)	(20)	(65)	(58)
Other	—	—	3	2
Total other (income) and deductions	86	80	269	229
Income before income taxes	263	233	559	436
Income tax benefit	(18)	(62)	(109)	(104)




Net income attributable to Alliant Energy common shareowners	$281	$295	$668	$540
Weighted average number of common shares outstanding:
Basic	257.0	256.6	256.9	256.4
Diluted	257.8	256.9	257.5	256.7
Earnings per weighted average common share attributable to Alliant Energy common shareowners:
Basic	$1.09	$1.15	$2.60	$2.11
Diluted	$1.09	$1.15	$2.59	$2.10

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)


	September 30, 2025	December 31, 2024
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$503	$81
Short-term investments	250	—
Accounts receivable, less allowance for expected credit losses	485	427

Production fuel, at weighted average cost	37	54
Gas stored underground, at weighted average cost	55	55
Materials and supplies, at weighted average cost	189	186
Regulatory assets	132	210

Other	193	171
Total current assets	1,844	1,184
Property, plant and equipment, net	19,813	18,701
Investments:
ATC Holdings	459	415
Other	230	224
Total investments	689	639
Other assets:
Regulatory assets	2,171	2,064
Deferred charges and other	110	126
Total other assets	2,281	2,190
Total assets	$24,627	$22,714


LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt	$1,074	$1,171
Commercial paper	192	558

Accounts payable	550	532

Regulatory liabilities	58	69
Other	360	385
Total current liabilities	2,234	2,715
Long-term debt, net (excluding current portion)	10,655	8,677
Other liabilities:
Deferred tax liabilities	2,187	2,188
Regulatory liabilities	1,076	959
Pension and other benefit obligations	197	224
Other	971	947
Total other liabilities	4,431	4,318
Commitments and contingencies (Note 1 3)
Equity:
Alliant Energy Corporation common equity:
Common stock - $0.01 par value - 480,000,000 shares authorized; 257,053,689 and 256,690,222 shares outstanding	3	3
Additional paid-in capital	3,087	3,060
Retained earnings	4,231	3,954
Accumulated other comprehensive income	—	1
Shares in deferred compensation trust - 359,483 and 372,116 shares at a weighted average cost of $38.39 and $36.56 per share	(14)	(14)
Total Alliant Energy Corporation common equity	7,307	7,004



Total liabilities and equity	$24,627	$22,714

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)


	For the Nine Months
	Ended September 30,
	2025	2024
	(in millions)
Cash flows from operating activities:
Net income	$668	$540
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	631	571
Deferred tax benefit and tax credits	(125)	(103)


Asset valuation charge for IPL’s Lansing Generating Station	—	60
Other	2	(9)
Other changes in assets and liabilities:
Accounts receivable	(391)	(388)






Regulatory liabilities	107	(67)
Deferred income taxes (a)	101	222

Other	(93)	87
Net cash flows from operating activities	900	913
Cash flows used for investing activities:
Construction and acquisition expenditures:
Utility business	(1,487)	(1,280)
Other	(161)	(154)
Cash receipts on sold receivables	332	399
Purchases of short-term investments	(250)	—
Proceeds from sales of partial ownership interests in West Riverside	—	123
Other	(39)	(28)
Net cash flows used for investing activities	(1,605)	(940)
Cash flows from financing activities:
Common stock dividends	(391)	(369)

Proceeds from issuance of long-term debt	2,174	1,613
Payments to retire long-term debt	(300)	(305)
Net change in commercial paper	(366)	(145)


Other	10	—
Net cash flows from financing activities	1,127	794
Net increase in cash, cash equivalents and restricted cash	422	767
Cash, cash equivalents and restricted cash at beginning of period	81	63
Cash, cash equivalents and restricted cash at end of period	$503	$830
Supplemental cash flows information:
Cash (paid) received during the period for:
Interest	($373)	($326)
Income taxes, net (a)	$108	$158
Significant non-cash investing and financing activities:
Accrued capital expenditures	$246	$194
Beneficial interest obtained in exchange for securitized accounts receivable	$231	$212

(a)2025 and 2024 include $117 million and $172 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)


	For the Three Months		For the Nine Months
	Ended September 30,		Ended September 30,
	2025	2024	2025	2024
	(in millions)
Revenues:
Electric utility	$608	$523	$1,455	$1,318
Gas utility	27	27	185	175
Steam and other	12	11	36	34
Total revenues	647	561	1,676	1,527
Operating expenses:
Electric production fuel and purchased power	106	79	213	195
Electric transmission service	115	115	322	317
Cost of gas sold	7	8	89	85
Other operation and maintenance:
Asset valuation charge for IPL’s Lansing Generating Station	—	—	—	60
Other	108	96	275	281
Depreciation and amortization	116	100	346	294
Taxes other than income taxes	15	14	44	45
Total operating expenses	467	412	1,289	1,277
Operating income	180	149	387	250
Other (income) and deductions:
Interest expense	54	44	154	128
Allowance for funds used during construction	(15)	(13)	(37)	(34)
Other	(3)	(4)	(6)	(4)
Total other (income) and deductions	36	27	111	90
Income before income taxes	144	122	276	160
Income tax benefit	(21)	(68)	(98)	(112)


Net income	$165	$190	$374	$272

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

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)


	September 30, 2025	December 31, 2024
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$209	$29
Accounts receivable, less allowance for expected credit losses	252	192

Production fuel, at weighted average cost	16	30
Gas stored underground, at weighted average cost	26	25
Materials and supplies, at weighted average cost	111	113
Regulatory assets	68	77
Other	58	43
Total current assets	740	509
Property, plant and equipment, net	10,083	9,336
Other assets:
Regulatory assets	1,564	1,509
Deferred charges and other	46	53
Total other assets	1,610	1,562
Total assets	$12,433	$11,407


LIABILITIES AND EQUITY
Current liabilities:
Current maturities of long-term debt	$—	$300
Commercial paper	—	50
Accounts payable	289	263
Accounts payable to associated companies	52	47
Accrued taxes	74	77
Accrued interest	49	48
Regulatory liabilities	39	54
Other	78	89
Total current liabilities	581	928
Long-term debt, net (excluding current portion)	4,679	3,790
Other liabilities:
Deferred tax liabilities	1,235	1,179
Regulatory liabilities	519	492
Pension and other benefit obligations	42	46
Other	527	511
Total other liabilities	2,323	2,228
Commitments and contingencies (Note 1 3)
Equity:
Interstate Power and Light Company common equity:
Common stock - $2.50 par value - 24,000,000 shares authorized; 13,370,788 shares outstanding	33	33
Additional paid-in capital	3,497	3,212
Retained earnings	1,320	1,216
Total Interstate Power and Light Company common equity	4,850	4,461


Total liabilities and equity	$12,433	$11,407

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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INTERSTATE POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)


	For the Nine Months
	Ended September 30,
	2025	2024
	(in millions)
Cash flows from operating activities:
Net income	$374	$272
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	346	294

Deferred tax benefit and tax credits	(81)	(64)
Asset valuation charge for IPL’s Lansing Generating Station	—	60
Other	(16)	(1)
Other changes in assets and liabilities:
Accounts receivable	(392)	(392)




Regulatory assets	(72)	(36)


Regulatory liabilities	11	(65)

Deferred income taxes (a)	134	166

Other	(15)	(3)
Net cash flows from operating activities	289	231
Cash flows used for investing activities:
Construction and acquisition expenditures	(976)	(702)
Cash receipts on sold receivables	332	399
Other	(16)	(29)
Net cash flows used for investing activities	(660)	(332)
Cash flows from financing activities:
Common stock dividends	(270)	(151)
Capital contributions from parent	285	325
Proceeds from issuance of long-term debt	888	643
Payments to retire long-term debt	(300)	—
Net change in commercial paper	(50)	—
Other	(2)	(13)
Net cash flows from financing activities	551	804
Net increase in cash, cash equivalents and restricted cash	180	703
Cash, cash equivalents and restricted cash at beginning of period	29	53
Cash, cash equivalents and restricted cash at end of period	$209	$756
Supplemental cash flows information:
Cash (paid) received during the period for:
Interest	($153)	($122)
Income taxes, net (a)	$94	$114
Significant non-cash investing and financing activities:
Accrued capital expenditures	$152	$120
Beneficial interest obtained in exchange for securitized accounts receivable	$231	$212

(a)2025 and 2024 include $90 million and $89 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)


	For the Three Months		For the Nine Months
	Ended September 30,		Ended September 30,
	2025	2024	2025	2024
	(in millions)
Revenues:
Electric utility	$516	$476	$1,373	$1,261
Gas utility	24	22	181	147
Other	—	1	1	2
Total revenues	540	499	1,555	1,410
Operating expenses:
Electric production fuel and purchased power	133	112	351	298
Electric transmission service	51	49	152	148
Cost of gas sold	5	5	91	67
Other operation and maintenance	84	72	222	200
Depreciation and amortization	92	91	275	269
Taxes other than income taxes	13	14	42	41
Total operating expenses	378	343	1,133	1,023
Operating income	162	156	422	387
Other (income) and deductions:
Interest expense	43	42	129	124

Allowance for funds used during construction	(9)	(7)	(28)	(24)
Other	4	3	9	4
Total other (income) and deductions	38	38	110	104
Income before income taxes	124	118	312	283
Income tax expense (benefit)	1	4	(9)	13
Net income	$123	$114	$321	$270

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

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED)


	September 30, 2025	December 31, 2024
	(in millions, except per share and share amounts)
ASSETS
Current assets:
Cash and cash equivalents	$11	$51
Accounts receivable, less allowance for expected credit losses	218	220
Production fuel, at weighted average cost	21	24
Gas stored underground, at weighted average cost	29	30
Materials and supplies, at weighted average cost	72	69
Regulatory assets	64	133
Prepaid gross receipts tax	38	51
Other	53	57
Total current assets	506	635
Property, plant and equipment, net	9,166	8,861
Other assets:
Regulatory assets	607	555
Deferred charges and other	52	55
Total other assets	659	610
Total assets	$10,331	$10,106


LIABILITIES AND EQUITY
Current liabilities:

Commercial paper	$192	$183

Accounts payable	189	209

Accrued interest	41	44
Regulatory liabilities	19	15
Other	86	94
Total current liabilities	527	545
Long-term debt, net	3,372	3,370
Other liabilities:
Deferred tax liabilities	786	865
Regulatory liabilities	557	467

Pension and other benefit obligations	85	102
Other	665	656
Total other liabilities	2,093	2,090
Commitments and contingencies (Note 1 3)
Equity:
Wisconsin Power and Light Company common equity:
Common stock - $5 par value - 18,000,000 shares authorized; 13,236,601 shares outstanding	66	66
Additional paid-in capital	2,613	2,533
Retained earnings	1,660	1,502
Total Wisconsin Power and Light Company common equity	4,339	4,101


Total liabilities and equity	$10,331	$10,106

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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WISCONSIN POWER AND LIGHT COMPANY

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)


	For the Nine Months
	Ended September 30,
	2025	2024
	(in millions)
Cash flows from operating activities:
Net income	$321	$270
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation and amortization	275	269

Deferred tax benefit and tax credits	(60)	(45)
Other	(2)	(2)
Other changes in assets and liabilities:




Regulatory assets	24	62


Regulatory liabilities	96	(1)

Deferred income taxes (a)	(38)	60
Other	(43)	38
Net cash flows from operating activities	573	651
Cash flows used for investing activities:
Construction and acquisition expenditures	(511)	(578)
Proceeds from sales of partial ownership interests in West Riverside	—	123
Other	(19)	(9)
Net cash flows used for investing activities	(530)	(464)
Cash flows used for financing activities:
Common stock dividends	(163)	(147)
Capital contributions from parent	80	55
Proceeds from issuance of long-term debt	—	297

Net change in commercial paper	9	(318)


Other	(9)	(12)
Net cash flows used for financing activities	(83)	(125)
Net increase (decrease) in cash, cash equivalents and restricted cash	(40)	62
Cash, cash equivalents and restricted cash at beginning of period	51	7
Cash, cash equivalents and restricted cash at end of period	$11	$69
Supplemental cash flows information:
Cash (paid) received during the period for:
Interest	($136)	($123)
Income taxes, net (a)	($7)	$36
Significant non-cash investing and financing activities:
Accrued capital expenditures	$89	$68

(a)2025 and 2024 include $27 million and $83 million, respectively, of proceeds from renewable tax credits transferred to other corporate taxpayers.

Refer to accompanying Combined Notes to Condensed Consolidated Financial Statements.


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ALLIANT ENERGY CORPORATION

INTERSTATE POWER AND LIGHT COMPANY

WISCONSIN POWER AND LIGHT COMPANY

COMBINED NOTES TO CONDENSED CONSOLIDATED FINANCIAL STATEMENTS (UNAUDITED)

NOTE 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

NOTE 1(a) General - The interim unaudited Financial Statements included herein have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (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 2024 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 nine months ended September 30, 2025 are not necessarily indicative of results that may be expected for the year ending December 31, 2025.

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) Cash and Cash Equivalents - At September 30, 2025, cash and cash equivalents included money market fund investments of $477 million and $194 million for Alliant Energy and IPL, respectively, with weighted average interest rates of 4%.

Note 1(c) Short-term Investments - Short-term investments include investments that have original maturities of greater than 90 days and remaining maturities of less than one year, and are convertible to known amounts of cash. At September 30, 2025, short-term investments included time deposits of $250 million for Alliant Energy, with weighted average interest rates of 4%.

NOTE 1(d) Asset Retirement Obligations (AROs) - In the second quarter of 2024, substantially due to the enactment of the revised Coal Combustion Residuals Rule, Alliant Energy and IPL recorded a pre-tax non-cash charge of $20 million to “Other operation and maintenance” in their income statements for the nine months ended September 30, 2024 for the AROs allocated to IPL’s steam business for its Prairie Creek Generating Station and the retired Sixth Street Generating Station as established in prior rate reviews.

NOTE 2. REGULATORY MATTERS

Regulatory Assets and Regulatory Liabilities -

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


	Alliant Energy		IPL		WPL
	September 30, 2025	December 31, 2024	September 30, 2025	December 31, 2024	September 30, 2025	December 31, 2024
Tax-related	$1,069	$989	$932	$870	$137	$119
AROs	441	401	304	281	137	120
Pension and OPEB costs	301	315	151	157	150	158
Assets retired early	162	180	153	168	9	12
Non-service pension and OPEB costs	55	51	20	19	35	32
Derivatives	51	60	12	15	39	45

WPL’s Western Wisconsin gas distribution expansion investments	40	42	—	—	40	42
Commodity cost recovery	33	68	8	2	25	66



Other	151	168	52	74	99	94
	$2,303	$2,274	$1,632	$1,586	$671	$688

Assets retired early - IPL was previously allowed a full recovery of and a full return on the Lansing Generating Station from both its retail and wholesale customers. The IUC’s September 2024 order for IPL’s retail electric rate review for the October 2024 through September 2025 forward-looking Test Period included a return of the remaining net book value of Lansing, but did not include a return on the remaining net book value of Lansing, effective October 1, 2024. As a result, the return on the remaining net book value was no longer recoverable from IPL’s retail electric customers, and a pre-tax non-cash charge of $60 million was recorded to “Asset valuation charge for IPL’s Lansing Generating Station” in Alliant Energy’s and IPL’s income statements for the nine months ended September 30, 2024.


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


	Alliant Energy		IPL		WPL
	September 30, 2025	December 31, 2024	September 30, 2025	December 31, 2024	September 30, 2025	December 31, 2024
Tax-related	$658	$582	$301	$286	$357	$296
Cost of removal obligations	351	347	206	205	145	142
Derivatives	49	53	25	29	24	24





Other	76	46	26	26	50	20
	$1,134	$1,028	$558	$546	$576	$482

Tax-related - The increase in Alliant Energy’s and WPL’s tax-related regulatory liabilities was primarily due to tax benefits resulting from investment tax credits recognized by WPL for certain energy storage facilities in 2025.

NOTE 3. PROPERTY, PLANT AND EQUIPMENT

Construction costs associated with WPL’s approximately 1,100 MW of new solar generation exceeded the construction cost estimates previously approved by the PSCW by approximately $205 million. In September 2025, WPL filed a settlement agreement with the PSCW for the 2026/2027 forward-looking Test Period. In November 2025, the PSCW issued an oral decision approving the settlement, which includes a full return of and on these solar generation construction costs from WPL’s retail electric customers. As a result, Alliant Energy and WPL concluded that there was not a probable disallowance of the higher rate base amounts as of September 30, 2025. A written order from the PSCW is currently expected by the end of 2025.

As of December 31, 2024, WPL planned to cease coal operations at Columbia Units 1 and 2 by the end of 2029, and Alliant Energy and WPL concluded that Columbia Units 1 and 2 met the criteria to be considered probable of abandonment. WPL currently plans to continue coal operations at Columbia Units 1 and 2 at least through 2029 as well as evaluate the potential conversion of Columbia Unit 1 and/or Unit 2 to natural gas. As a result, as of September 30, 2025, Alliant Energy and WPL concluded that Columbia Units 1 and 2 (net book value of $398 million) no longer meet the criteria to be considered probable of abandonment.

NOTE 4. RECEIVABLES

Sales of Accounts Receivable - IPL maintains a Receivables Purchase and Sale Agreement (Receivables Agreement) whereby it may sell its customer accounts receivables, unbilled revenues and certain other accounts receivables to a third party through wholly-owned and consolidated special purpose entities. The transfers of receivables meet the criteria for sale accounting established by the transfer of financial assets accounting rules. Effective September 2025, the limit on cash proceeds under the Receivables Agreement was changed to $5 million. As of September 30, 2025, IPL had $4 million of available capacity under its sales of accounts receivable program. IPL’s maximum and average outstanding aggregate cash proceeds (based on daily outstanding balances) related to the sales of accounts receivable program for the three and nine months ended September 30 were as follows (in millions):


	Three Months		Nine Months
	2025	2024	2025	2024
Maximum outstanding aggregate cash proceeds	$110	$52	$110	$110
Average outstanding aggregate cash proceeds	28	7	65	34

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


	September 30, 2025	December 31, 2024
Customer accounts receivable	$166	$137
Unbilled utility revenues	79	108
Other receivables	1	—
Receivables sold to third party	246	245
Less: cash proceeds	1	70
Deferred proceeds	245	175
Less: allowance for expected credit losses	14	12
Fair value of deferred proceeds	$231	$163


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As of September 30, 2025, outstanding receivables past due under the Receivables Agreement were $19 million. Additional attributes of IPL’s receivables sold under the Receivables Agreement for the three and nine months ended September 30 were as follows (in millions):


	Three Months		Nine Months
	2025	2024	2025	2024
Collections	$681	$565	$1,732	$1,578
Write-offs, net of recoveries	5	4	9	9

NOTE 5. INVESTMENTS

Unconsolidated Equity Investments - Alliant Energy’s equity (income) loss from unconsolidated investments accounted for under the equity method of accounting for the three and nine months ended September 30 was as follows (in millions):


	Three Months		Nine Months
	2025	2024	2025	2024
ATC Holdings	($15)	($13)	($43)	($38)
Non-utility wind farm in Oklahoma	(2)	(2)	(6)	(5)
Corporate venture investments	(1)	2	10	1
Other	—	(1)	(2)	(2)
	($18)	($14)	($41)	($44)

NOTE 6. COMMON EQUITY

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


Shares outstanding, January 1, 2025			256,690,222


Shareowner Direct Plan			277,090
Equity-based compensation plans			86,377

Shares outstanding, September 30, 2025			257,053,689

At-the-Market Offering Program - In May 2025, Alliant Energy filed a prospectus supplement and executed a related distribution agreement, under which it may sell up to $1.3 billion in aggregate of its common stock through 2028 through an at-the-market offering program that includes an equity forward sales component. 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 at-the-market offering program with various counterparties who, for the three and nine months ended September 30, 2025, borrowed and sold an aggregate of 7,851,080 and 10,764,103 shares of Alliant Energy common stock at an aggregate gross sales price of $508 million and $686 million, including approximately $4 million and $5 million in commissions, respectively, 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 in 2026 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 September 30, 2025, the weighted-average forward price, net of commissions, was $63.46 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 September 30, 2025, Alliant Energy could have settled all of its outstanding forward sale agreements under the at-the-market offering program with physical delivery of 10,764,103 shares of Alliant Energy common stock to the counterparties in exchange for cash of $683 million.

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. As of September 30, 2025, 199,923 incremental shares were included in the calculation of diluted EPS related to the securities under the forward sale agreements.


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Changes in Shareowners’ Equity - A summary of changes in shareowners’ equity was as follows (in millions):



Alliant Energy				Accumulated	Shares in
		Additional		Other	Deferred	Total
	Common	Paid-In	Retained	Comprehensive	Compensation	Common
	Stock	Capital	Earnings	Income (Loss)	Trust	Equity
Three Months Ended September 30, 2025
Beginning balance, June 30, 2025	$3	$3,075	$4,080	$—	($13)	$7,145
Net income attributable to Alliant Energy common shareowners			281			281
Common stock dividends ($0.5075 per share)			(130)			(130)
Shareowner Direct Plan issuances		6				6
Equity-based compensation plans and other		6			(1)	5




Ending balance, September 30, 2025	$3	$3,087	$4,231	$—	($14)	$7,307
Three Months Ended September 30, 2024
Beginning balance, June 30, 2024	$3	$3,042	$3,755	$3	($12)	$6,791
Net income attributable to Alliant Energy common shareowners			295			295
Common stock dividends ($0.48 per share)			(123)			(123)
Shareowner Direct Plan issuances		6				6
Equity-based compensation plans and other		4			(1)	3



Other comprehensive loss, net of tax				(4)		(4)
Ending balance, September 30, 2024	$3	$3,052	$3,927	($1)	($13)	$6,968




Alliant Energy				Accumulated	Shares in
		Additional		Other	Deferred	Total
	Common	Paid-In	Retained	Comprehensive	Compensation	Common
	Stock	Capital	Earnings	Income (Loss)	Trust	Equity
Nine Months Ended September 30, 2025
Beginning balance, December 31, 2024	$3	$3,060	$3,954	$1	($14)	$7,004
Net income attributable to Alliant Energy common shareowners			668			668
Common stock dividends ($1.5225 per share)			(391)			(391)
Shareowner Direct Plan issuances		18				18
Equity-based compensation plans and other		9				9



Other comprehensive loss, net of tax				(1)		(1)
Ending balance, September 30, 2025	$3	$3,087	$4,231	$—	($14)	$7,307
Nine Months Ended September 30, 2024
Beginning balance, December 31, 2023	$3	$3,030	$3,756	$1	($13)	$6,777
Net income attributable to Alliant Energy common shareowners			540			540
Common stock dividends ($1.44 per share)			(369)			(369)
Shareowner Direct Plan issuances		18				18
Equity-based compensation plans and other		4				4



Other comprehensive loss, net of tax				(2)		(2)
Ending balance, September 30, 2024	$3	$3,052	$3,927	($1)	($13)	$6,968



IPL		Additional		Total
	Common	Paid-In	Retained	Common
	Stock	Capital	Earnings	Equity
Three Months Ended September 30, 2025
Beginning balance, June 30, 2025	$33	$3,357	$1,245	$4,635
Net income			165	165
Common stock dividends			(90)	(90)
Capital contributions from parent		140		140
Ending balance, September 30, 2025	$33	$3,497	$1,320	$4,850
Three Months Ended September 30, 2024
Beginning balance, June 30, 2024	$33	$3,012	$1,035	$4,080
Net income			190	190
Common stock dividends			(50)	(50)
Capital contributions from parent		200		200
Ending balance, September 30, 2024	$33	$3,212	$1,175	$4,420


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IPL		Additional		Total
	Common	Paid-In	Retained	Common
	Stock	Capital	Earnings	Equity
Nine Months Ended September 30, 2025
Beginning balance, December 31, 2024	$33	$3,212	$1,216	$4,461
Net income			374	374
Common stock dividends			(270)	(270)
Capital contributions from parent		285		285
Ending balance, September 30, 2025	$33	$3,497	$1,320	$4,850
Nine Months Ended September 30, 2024
Beginning balance, December 31, 2023	$33	$2,887	$1,054	$3,974
Net income			272	272
Common stock dividends			(151)	(151)
Capital contributions from parent		325		325
Ending balance, September 30, 2024	$33	$3,212	$1,175	$4,420



WPL		Additional		Total
	Common	Paid-In	Retained	Common
	Stock	Capital	Earnings	Equity
Three Months Ended September 30, 2025
Beginning balance, June 30, 2025	$66	$2,533	$1,581	$4,180
Net income			123	123
Common stock dividends			(44)	(44)
Capital contributions from parent		80		80



Ending balance, September 30, 2025	$66	$2,613	$1,660	$4,339
Three Months Ended September 30, 2024
Beginning balance, June 30, 2024	$66	$2,533	$1,411	$4,010
Net income			114	114
Common stock dividends			(49)	(49)




Ending balance, September 30, 2024	$66	$2,533	$1,476	$4,075




WPL		Additional		Total
	Common	Paid-In	Retained	Common
	Stock	Capital	Earnings	Equity
Nine Months Ended September 30, 2025
Beginning balance, December 31, 2024	$66	$2,533	$1,502	$4,101
Net income			321	321
Common stock dividends			(163)	(163)
Capital contributions from parent		80		80



Ending balance, September 30, 2025	$66	$2,613	$1,660	$4,339
Nine Months Ended September 30, 2024
Beginning balance, December 31, 2023	$66	$2,478	$1,353	$3,897
Net income			270	270
Common stock dividends			(147)	(147)
Capital contributions from parent		55		55



Ending balance, September 30, 2024	$66	$2,533	$1,476	$4,075

NOTE 7. DEBT

NOTE 7(a) Short-term Debt - In March 2025, Alliant Energy, IPL and WPL reallocated credit facility capacity amounts to $550 million for Alliant Energy at the parent company level, $350 million for IPL and $400 million for WPL, within the $1.3 billion total commitment. Information regarding commercial paper and borrowings under the single credit facility classified as short-term debt was as follows (dollars in millions):


September 30, 2025	Alliant Energy	IPL	WPL
Amount outstanding	$192	$—	$192
Weighted average interest rates	4.3%	N/A	4.3%
Available credit facility capacity	$1,108	$350	$208


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	Alliant Energy		IPL		WPL
Three Months Ended September 30	2025	2024	2025	2024	2025	2024
Maximum amount outstanding (based on daily outstanding balances)	$372	$330	$78	$—	$297	$—
Average amount outstanding (based on daily outstanding balances)	$263	$197	$9	$—	$177	$—
Weighted average interest rates	4.5%	5.4%	4.6%	N/A	4.5%	N/A
Nine Months Ended September 30
Maximum amount outstanding (based on daily outstanding balances)	$741	$632	$141	$19	$297	$390
Average amount outstanding (based on daily outstanding balances)	$417	$320	$32	$1	$187	$87
Weighted average interest rates	4.6%	5.5%	4.6%	5.5%	4.5%	5.5%

NOTE 7(b) Long-term Debt - In March 2025, AEF entered into a $300 million variable rate (5% as of September 30, 2025) term loan credit agreement (with Alliant Energy as guarantor), which expires in March 2026. This term loan credit agreement amended and restated the term loan credit agreement that expired in March 2025, and retired the $300 million variable rate term loan set forth therein, which was classified as a non-cash financing activity. AEF’s restated term loan credit agreement includes an option to increase the amount outstanding with one or more additional term loans in an aggregate amount not to exceed $100 million.

In May 2025, IPL issued $600 million of 5.6% senior debentures due 2035. The net proceeds from this issuance were used for the retirement of IPL’s senior debentures in July 2025 ($50 million, 5.5%) and August 2025 ($250 million, 3.4%), to reduce cash amounts received from its sale of accounts receivable program and commercial paper classified as long-term debt, and for general corporate purposes.

In September 2025, IPL issued $300 million of 5.6% senior debentures due 2055. The net proceeds from this issuance were used to reduce cash amounts received from its sale of accounts receivable program, reduce its outstanding commercial paper and for general corporate purposes.

In September 2025, Alliant Energy issued $725 million of junior subordinated notes due 2056. The notes will bear interest at 5.75% until April 1, 2031. The interest rate will reset every 5 years beginning April 1, 2031, to equal the then-current five-year U.S. Treasury rate plus a spread of 2.077%, provided the interest rate will not reset below 5.75%. A portion of the net proceeds from this issuance were placed in time deposits and money market fund investments pending the retirement of AEF’s $200 million of 1.40% senior notes, AEF’s $300 million variable rate term loan and Alliant Energy’s $575 million of 3.875% convertible senior notes, each of which matures in March 2026 and is expected to be retired at or prior to maturity. The remainder of the net proceeds were used to reduce outstanding commercial paper and for general corporate purposes.

Convertible Senior Notes - In May 2025, Alliant Energy issued $575 million of 3.25% convertible senior notes (the 2028 Notes), which are senior unsecured obligations, and used the net proceeds from the issuance to reduce Alliant Energy’s outstanding commercial paper and for general corporate purposes. The 2028 Notes will mature on May 30, 2028 unless earlier converted or repurchased, and no sinking fund is provided for the 2028 Notes. Alliant Energy may not redeem the 2028 Notes prior to the maturity date. Holders may convert their 2028 Notes at their option at any time prior to the close of business on the business day immediately preceding March 1, 2028 only under the following circumstances:

•during any calendar quarter commencing after the calendar quarter ending on September 30, 2025 (and only during such calendar quarter), if the last reported sale price of Alliant Energy’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day during such period;

•during the 5 business day period after any 10 consecutive trading day period (the “measurement period”) in which the trading price (as defined in the related Indenture) per $1,000 principal amount of 2028 Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of Alliant Energy’s common stock and the conversion rate on each such trading day; or

•upon the occurrence of specified corporate events.

On or after March 1, 2028 until the close of business on the business day immediately preceding the maturity date, holders may convert all or any portion of their 2028 Notes at any time, regardless of the foregoing circumstances. Upon conversion of the 2028 Notes, Alliant Energy will pay cash up to the aggregate principal amount of the 2028 Notes to be converted and pay or deliver, as the case may be, cash, shares of its common stock or a combination of cash and shares of its common stock, at its election, in respect of the remainder, if any, of its conversion obligation in excess of the aggregate principal amount of the 2028 Notes being converted.


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The initial conversion rate is 13.1773 shares of common stock per $1,000 principal amount of 2028 Notes (equivalent to an initial conversion price of approximately $75.89 per share of Alliant Energy’s common stock). The conversion rate is subject to adjustment in some events but will not be adjusted for any accrued and unpaid interest. In addition, following certain corporate events that occur prior to the maturity date, Alliant Energy will, in certain circumstances, increase the conversion rate for a holder who elects to convert its 2028 Notes in connection with such a corporate event.

If Alliant Energy undergoes a fundamental change (as defined in the related Indenture), then, subject to certain conditions, holders of the 2028 Notes may require Alliant Energy to repurchase for cash all or any portion of its 2028 Notes at a fundamental change repurchase price equal to 100% of the principal amount of the 2028 Notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date.

As of September 30, 2025, the conditions allowing holders of the 2028 Notes and Alliant Energy’s convertible senior notes due 2026 (the 2026 Notes) to convert their respective notes were not met, and the 2028 Notes were classified as “Long-term debt, net” and the 2026 Notes were classified as “Current maturities of long-term debt,” on Alliant Energy’s balance sheet. As of September 30, 2025, the net carrying amount was $569 million and $574 million, with unamortized debt issuance costs of $6 million and $1 million, and the estimated fair value (Level 2) was $593 million and $619 million for the 2028 Notes and 2026 Notes, respectively. As of September 30, 2025, no shares of Alliant Energy’s common stock and 27,905 shares of Alliant Energy’s common stock related to the potential conversion of the 2028 Notes and 2026 Notes, respectively, were included in diluted EPS based on Alliant Energy’s average stock prices and the relevant terms of the respective notes.

NOTE 8. 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 September 30	2025	2024	2025	2024	2025	2024
Electric Utility:
Retail - residential	$408	$378	$215	$202	$193	$176
Retail - commercial	282	239	192	153	90	86
Retail - industrial	306	270	167	142	139	128
Wholesale	51	58	11	19	40	39
Bulk power and other	77	54	23	7	54	47
Total Electric Utility	1,124	999	608	523	516	476
Gas Utility:
Retail - residential	24	24	12	13	12	11
Retail - commercial	13	13	7	7	6	6
Retail - industrial	1	1	1	1	—	—
Transportation/other	13	11	7	6	6	5
Total Gas Utility	51	49	27	27	24	22
Other Utility:
Steam	9	9	9	9	—	—
Other utility	3	3	3	2	—	1
Total Other Utility	12	12	12	11	—	1
Non-Utility and Other:
Travero and other	23	21	—	—	—	—

Total Non-Utility and Other	23	21	—	—	—	—
Total revenues	$1,210	$1,081	$647	$561	$540	$499


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	Alliant Energy		IPL		WPL
Nine Months Ended September 30	2025	2024	2025	2024	2025	2024
Electric Utility:
Retail - residential	$1,027	$966	$512	$502	$515	$464
Retail - commercial	705	616	462	385	243	231
Retail - industrial	782	730	403	372	379	358
Wholesale	148	147	39	45	109	102
Bulk power and other	166	120	39	14	127	106
Total Electric Utility	2,828	2,579	1,455	1,318	1,373	1,261
Gas Utility:
Retail - residential	211	189	107	103	104	86
Retail - commercial	106	92	49	48	57	44
Retail - industrial	10	8	6	5	4	3
Transportation/other	39	33	23	19	16	14
Total Gas Utility	366	322	185	175	181	147
Other Utility:
Steam	28	29	28	29	—	—
Other utility	9	7	8	5	1	2
Total Other Utility	37	36	36	34	1	2
Non-Utility and Other:
Travero and other	67	68	—	—	—	—

Total Non-Utility and Other	67	68	—	—	—	—
Total revenues	$3,298	$3,005	$1,676	$1,527	$1,555	$1,410

NOTE 9. INCOME TAXES

Income Tax Rates - Overall effective income tax rates for the three and nine months ended September 30, which were computed by dividing income tax expense (benefit) by income before income taxes, were as follows. The effective income tax rates were different than the federal statutory rate primarily due to state income taxes, production tax credits, 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 nine months ended September 30, 2024 were the pre-tax non-cash charge of $60 million for IPL’s Lansing Generating Station discussed in Note 2 and the pre-tax non-cash charge of $20 million for the AROs allocated to IPL’s steam business discussed in Note 1(d). Alliant Energy’s, IPL’s and WPL’s effective income tax rates for the three and nine months ended September 30, 2025 were also impacted by additional tax credits in 2025 from renewable generation and energy storage projects placed in service in 2024 and/or expected to be placed in service in 2025.


	Alliant Energy				IPL				WPL
	Three Months		Nine Months		Three Months		Nine Months		Three Months		Nine Months
	2025	2024	2025	2024	2025	2024	2025	2024	2025	2024	2025	2024
Overall income tax rate	(7%)	(27%)	(19%)	(24%)	(15%)	(56%)	(36%)	(70%)	1%	3%	(3%)	5%

Deferred Tax Assets and Liabilities -

Carryforwards - At September 30, 2025, the carryforwards and expiration dates were estimated as follows (in millions):


	Range of Expiration Dates	Alliant Energy	IPL	WPL

State net operating losses	2025-2045	$249	$7	$1
Federal tax credits	2034-2045	741	464	263

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. Alliant Energy currently expects an increase in total state income tax apportionment primarily due to an increase in projected electric utility revenues driven by demand for energy from commercial and industrial customers, including demand from IPL’s and WPL’s executed electric service agreements with customers who expect to build data centers in their service territories. Alliant Energy parent company’s deferred tax assets were remeasured to reflect an increase in estimated total state income tax apportionment, which resulted in a charge of $8 million recorded to income tax expense in Alliant Energy’s income statement and an increase in deferred tax liabilities on Alliant Energy’s balance sheet in the third quarter of 2025.


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NOTE 10. BENEFIT PLANS

NOTE 10(a) Pension and OPEB Plans -

Net Periodic Benefit Costs - The components of net periodic benefit costs for sponsored defined benefit pension and OPEB plans for the three and nine months ended September 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		Nine Months		Three Months		Nine Months
Alliant Energy	2025	2024	2025	2024	2025	2024	2025	2024
Service cost	$1	$1	$3	$3	$—	$1	$1	$2
Interest cost	11	12	34	34	2	2	6	6
Expected return on plan assets	(13)	(14)	(40)	(41)	—	(2)	(3)	(4)
Amortization of prior service credit	(1)	—	(1)	—	—	—	—	—
Amortization of actuarial loss	6	6	17	18	—	—	—	—


	$4	$5	$13	$14	$2	$1	$4	$4


	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Nine Months		Three Months		Nine Months
IPL	2025	2024	2025	2024	2025	2024	2025	2024
Service cost	$1	$1	$2	$2	$—	$—	$—	$—
Interest cost	5	5	15	15	—	1	2	3
Expected return on plan assets	(7)	(7)	(19)	(20)	(1)	(1)	(3)	(3)

Amortization of actuarial loss	3	2	7	7	—	—	—	—
	$2	$1	$5	$4	($1)	$—	($1)	$—


	Defined Benefit Pension Plans				OPEB Plans
	Three Months		Nine Months		Three Months		Nine Months
WPL	2025	2024	2025	2024	2025	2024	2025	2024
Service cost	$—	$—	$1	$1	$—	$—	$—	$—
Interest cost	5	5	15	15	1	1	2	3
Expected return on plan assets	(5)	(6)	(17)	(18)	(1)	(1)	(1)	(1)

Amortization of actuarial loss	3	3	8	9	—	—	—	—

	$3	$2	$7	$7	$—	$—	$1	$2

NOTE 10(b) Equity-based Compensation Plans - A summary of compensation expense, including amounts allocated to IPL and WPL, and the related income tax benefits recognized for share-based compensation awards for the three and nine months ended September 30 was as follows (in millions):


	Alliant Energy				IPL				WPL
	Three Months		Nine Months		Three Months		Nine Months		Three Months		Nine Months
	2025	2024	2025	2024	2025	2024	2025	2024	2025	2024	2025	2024
Compensation expense	$6	$3	$13	$10	$3	$2	$7	$5	$2	$1	$6	$4
Income tax benefits	2	1	4	3	1	—	2	1	1	—	2	1

As of September 30, 2025, Alliant Energy’s, IPL’s and WPL’s total unrecognized compensation cost related to share-based compensation awards was $17 million, $8 million and $8 million, respectively, which is expected to be recognized over a weighted average period of between 1 year and 2 years.

For the nine months ended September 30, 2025, performance shares and restricted stock units were granted to key employees under the equity-based compensation plans as follows. These shares and units will be paid out in shares of common stock, and are therefore accounted for as equity awards.


		Weighted Average
	Grants	Grant Date Fair Value
Performance shares (total shareowner return metric)	105,896	$66.52
Performance shares (net income and environmental metrics)	118,883	61.63
Restricted stock units	100,245	61.66

As of September 30, 2025, 598,077 shares were included in the calculation of diluted EPS related to the nonvested equity awards.


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NOTE 11. DERIVATIVE INSTRUMENTS

Commodity Derivatives -

Notional Amounts - As of September 30, 2025, 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		Diesel Fuel
	MWhs	Years	MWhs	Years	Dths	Years		Gallons	Years
Alliant Energy	1,689	2025-2026	17,992	2025-2026	136,910	2025-2032		630	2025
IPL	563	2025-2026	7,143	2025-2026	56,355	2025-2030		—	—
WPL	1,126	2025-2026	10,849	2025-2026	80,555	2025-2032		630	2025

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
	September 30, 2025	December 31, 2024	September 30, 2025	December 31, 2024	September 30, 2025	December 31, 2024
Current derivative assets	$55	$41	$38	$29	$17	$12
Non-current derivative assets	27	34	14	19	13	15
Current derivative liabilities	22	26	8	11	14	15
Non-current derivative liabilities	26	32	2	2	24	30

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 September 30, 2025 and December 31, 2024, 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.

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
September 30, 2025
Derivative assets	$82	$72	$52	$47	$30	$25
Derivative liabilities	48	38	10	5	38	33
December 31, 2024
Derivative assets	75	64	48	43	27	21
Derivative liabilities	58	47	13	8	45	39

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.


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NOTE 12. FAIR VALUE MEASUREMENTS

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


Alliant Energy	September 30, 2025					December 31, 2024
		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	$477	$477	$—	$—	$477	$52	$52	$—	$—	$52
Time deposits	250	—	250	—	250	—	—	—	—	—
Commodity derivatives	82	—	42	40	82	75	—	48	27	75

Deferred proceeds	231	—	—	231	231	163	—	—	163	163
Liabilities:
Commodity derivatives	48	—	47	1	48	58	—	56	2	58

Long-term debt (incl. current maturities)	11,729	—	11,504	—	11,504	9,848	—	9,577	—	9,577


IPL	September 30, 2025					December 31, 2024
		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	$194	$194	$—	$—	$194	$9	$9	$—	$—	$9
Commodity derivatives	52	—	21	31	52	48	—	26	22	48
Deferred proceeds	231	—	—	231	231	163	—	—	163	163
Liabilities:
Commodity derivatives	10	—	9	1	10	13	—	11	2	13
Long-term debt (incl. current maturities)	4,679	—	4,465	—	4,465	4,090	—	3,736	—	3,736


WPL	September 30, 2025					December 31, 2024
		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	$—	$—	$—	$—	$—	$43	$43	$—	$—	$43
Commodity derivatives	30	—	21	9	30	27	—	22	5	27
Liabilities:
Commodity derivatives	38	—	38	—	38	45	—	45	—	45
Long-term debt	3,372	—	3,287	—	3,287	3,370	—	3,170	—	3,170

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 September 30	2025	2024	2025	2024
Beginning balance, July 1	$56	$51	$235	$171
Total net gains (losses) included in changes in net assets (realized/unrealized)	(2)	2	—	—



Sales	(2)	—	—	—
Settlements (a)	(13)	(16)	(4)	41
Ending balance, September 30	$39	$37	$231	$212
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30	($4)	$2	$—	$—


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Alliant Energy	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
Nine Months Ended September 30	2025	2024	2025	2024
Beginning balance, January 1	$25	$24	$163	$216
Total net gains (losses) included in changes in net assets (realized/unrealized)	5	(7)	—	—


Purchases	50	59	—	—
Sales	(2)	(1)	—	—
Settlements (a)	(39)	(38)	68	(4)
Ending balance, September 30	$39	$37	$231	$212
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30	$4	($7)	$—	$—


IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
Three Months Ended September 30	2025	2024	2025	2024
Beginning balance, July 1	$44	$40	$235	$171
Total net losses included in changes in net assets (realized/unrealized)	(5)	—	—	—



Sales	(1)	—	—	—
Settlements (a)	(8)	(11)	(4)	41
Ending balance, September 30	$30	$29	$231	$212
The amount of total net losses for the period included in changes in net assets attributable to the change in unrealized losses relating to assets and liabilities held at September 30	($6)	$—	$—	$—



IPL	Commodity Contract Derivative
	Assets and (Liabilities), net		Deferred Proceeds
Nine Months Ended September 30	2025	2024	2025	2024
Beginning balance, January 1	$20	$19	$163	$216
Total net gains (losses) included in changes in net assets (realized/unrealized)	1	(7)	—	—


Purchases	40	45	—	—
Sales	(1)	(1)	—	—
Settlements (a)	(30)	(27)	68	(4)
Ending balance, September 30	$30	$29	$231	$212
The amount of total net gains (losses) for the period included in changes in net assets attributable to the change in unrealized gains (losses) relating to assets and liabilities held at September 30	$1	($7)	$—	$—


WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Three Months Ended September 30	2025	2024
Beginning balance, July 1	$12	$11
Total net gains included in changes in net assets (realized/unrealized)	3	2



Sales	(1)	—
Settlements	(5)	(5)
Ending balance, September 30	$9	$8
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 September 30	$2	$2


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WPL	Commodity Contract Derivative
	Assets and (Liabilities), net
Nine Months Ended September 30	2025	2024
Beginning balance, January 1	$5	$5
Total net gains included in changes in net assets (realized/unrealized)	4	—


Purchases	10	14
Sales	(1)	—
Settlements	(9)	(11)
Ending balance, September 30	$9	$8
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 September 30	$3	$—

(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
September 30, 2025	$3	$36	$3	$27	$—	$9
December 31, 2024	—	25	—	20	—	5

NOTE 13. COMMITMENTS AND CONTINGENCIES

NOTE 13(a) Capital Purchase Commitments - Various contractual obligations contain minimum future commitments related to capital expenditures for certain construction projects, including improvements at the natural gas-fired Neenah Energy Facility and Sheboygan Falls Energy Facility, and IPL’s and WPL’s expansion of energy storage. At September 30, 2025, Alliant Energy’s, IPL’s and WPL’s minimum future commitments for these projects were $332 million, $136 million and $193 million, respectively.

NOTE 13(b) Other Purchase Commitments - Various commodity supply, transportation and storage contracts help meet obligations to provide electricity and natural gas to utility customers. In addition, there are various purchase commitments associated with other goods and services. At September 30, 2025, the related minimum future commitments, excluding amounts for purchased power commitments that do not have minimum thresholds but will require payment when electricity is generated by the provider, were as follows (in millions):


	Alliant Energy	IPL	WPL
Natural gas	$879	$489	$390
Coal	149	52	97

Other (a)	110	52	26
	$1,138	$593	$513

(a)Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2025.

NOTE 13(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 September 30, 2025, the currently known partnership obligations for the abandonment obligations are estimated at $54 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 September 30, 2025 and December 31, 2024.


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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 September 30, 2025 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 September 30, 2025 and December 31, 2024.

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 September 30, 2025, IPL and WPL provided indemnifications associated with $283 million and $148 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 September 30, 2025, IPL’s and WPL’s related guarantees were approximately $35 million and $44 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 September 30, 2025.

NOTE 13(d) Environmental Matters -

Manufactured Gas Plant (MGP) Sites - IPL and WPL have current or previous ownership interests in various sites that are previously associated with the production of gas for which IPL and WPL have, or may have in the future, liability for investigation, remediation and monitoring costs. IPL and WPL are working pursuant to the requirements of various federal and state agencies to investigate, mitigate, prevent and remediate, where necessary, the environmental impacts to property, including natural resources, at and around these former MGP sites in order to protect public health and the environment. At September 30, 2025, 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	$7	-	$29	$5	-	$18	$2	-	$11
Current and non-current environmental liabilities	$12			$8			$4

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

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


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NOTE 14. SEGMENTS OF BUSINESS

Certain financial information relating to Alliant Energy’s, IPL’s and WPL’s reportable segments, which represents the services provided to their customers, and reconciliation to consolidated amounts, was as follows (in millions):


	Utility
			Total		Alliant
			Reportable		Energy
Three Months Ended September 30, 2025	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$608	$516	$1,124	N/A	$1,124
Gas utility revenues	27	24	51	N/A	51
Other revenues	12	—	12	$23	35
Total revenues	647	540	1,187	23	1,210
Electric production fuel and purchased power expense	106	133	239	N/A	239
Electric transmission service expense	115	51	166	N/A	166
Cost of gas sold expense	7	5	12	N/A	12

Other operation and maintenance expense	108	84	192	12	204
Other segment items:
Depreciation and amortization expense	116	92	208	3	211
Interest expense	54	43	97	31	128
Equity income from unconsolidated investments, net	—	(1)	(1)	(17)	(18)
Income tax expense (benefit)	(21)	1	(20)	2	(18)
Other (a)	(3)	9	6	(1)	5
Net income (loss)	165	123	288	(7)	281
Total assets (as of September 30, 2025)	12,433	10,331	22,764	1,863	24,627
Investments in equity method subsidiaries (as of September 30, 2025)	5	19	24	644	668
Construction and acquisition expenditures	348	163	511	72	583


	Utility
			Total		Alliant
Three Months Ended September 30, 2024 (amounts may not foot due to rounding)			Reportable		Energy
	IPL	WPL	Segments	Other	Consolidated
Electric utility revenues	$523	$476	$999	N/A	$999
Gas utility revenues	27	22	49	N/A	49
Other revenues	11	1	12	$21	33
Total revenues	561	499	1,060	21	1,081
Electric production fuel and purchased power expense	79	112	191	N/A	192
Electric transmission service expense	115	49	164	N/A	165
Cost of gas sold expense	8	5	13	N/A	13

Other operation and maintenance expense	96	72	168	6	174
Other segment items:
Depreciation and amortization expense	100	91	191	4	195
Interest expense	44	42	86	28	114
Equity income from unconsolidated investments, net	—	(1)	(1)	(13)	(14)
Income tax expense (benefit)	(68)	4	(64)	2	(62)
Other (a)	(3)	11	8

ALLIANT ENERGY CORP 10-Q