LNT

EX-99.1

2 lnt043020268-kex991.htm

EX-99.1

Document

Exhibit 99.1

Alliant Energy Corporation

Corporate Headquarters

4902 North Biltmore Lane

Madison, WI 53718-2148

www.alliantenergy.com

News Release

FOR IMMEDIATE RELEASE

ALLIANT ENERGY ANNOUNCES FIRST QUARTER 2026 RESULTS

•First quarter GAAP earnings per share were $0.87 in 2026, compared to $0.83 in 2025

•First quarter ongoing earnings per share were $0.82 in 2026, compared to $0.83 in 2025

•Reaffirming 2026 ongoing earnings guidance range of $3.36 - $3.46 per share

•Signed an approximately 370 MW electric service agreement in Iowa, total contracted data center demand is now approximately 3.4 GW

MADISON, Wis. - April 30, 2026 - Alliant Energy Corporation (NASDAQ: LNT) today announced U.S. generally accepted accounting principles (GAAP) consolidated unaudited earnings per share (EPS) of $0.87 for first quarter 2026, compared to $0.83 for the first quarter of 2025. Ongoing EPS for first quarter 2026 was $0.82, compared to $0.83 for the first quarter of 2025.

Alliant Energy reaffirmed its consolidated ongoing EPS guidance for 2026 of $3.36 - $3.46, continuing its over a decade strong track record of compound annual earnings growth of more than 6%.

“We are off to a strong start in 2026, delivering approximately 25% of our ongoing earnings guidance midpoint, and reaffirming our full-year ongoing EPS outlook,” said Lisa Barton, Alliant Energy President and CEO. “Our results reflect disciplined execution and continued momentum in data center growth, including the signing of a new electric service agreement in Iowa for approximately 370 megawatts of contracted demand. With five executed agreements, we are translating customer demand into well-structured, long-term growth that benefits investors, existing customers and communities.”

Alliant Energy Consolidated EPS:GAAP EPSNon-GAAP EPS

2026202520262025

Three months ended March 31$0.87$0.83$0.82$0.83

In 2026, the primary drivers of Alliant Energy’s results were higher revenue requirements from increasing rate base at IPL and WPL of $0.05 and $0.10 per share, respectively, including investments in generation and energy storage, non-GAAP adjustments in 2026, and higher allowance for funds used during construction. These items were offset by higher financing and depreciation expense related to capital investments, as well as other operating and maintenance expense primarily due to increased electric distribution and generation costs from planned maintenance activities and the addition of new energy resources.

Retail electric and gas sales decreased an estimated $0.04 and $0.03 per share in 2026 and 2025, respectively, due to impacts of temperatures on customer demand.

Alliant Energy’s Non-GAAP, or ongoing, EPS for 2026 excludes $0.05 per share benefit related to the remeasurement of deferred tax assets, reflecting a remeasurement of estimated state income tax apportionment. 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. This non-GAAP adjustment is presented to supplement GAAP results and highlight financial measures not typically associated with ongoing operations.

1

2026 Earnings Guidance

Alliant Energy is reaffirming its consolidated ongoing EPS guidance for 2026 of $3.36 - $3.46 per diluted share. Assumptions for Alliant Energy’s 2026 EPS guidance include, but are not limited to:

•Ability of IPL and WPL to earn their authorized rates of return

•Normal temperatures in its utility service territories

•Stable economy and resulting implications on utility sales

•Execution of capital expenditure plans, including achievement of targeted in-service dates

•Execution of cost controls and financing plans

•Consolidated effective tax rate of (29%)

The 2026 earnings guidance does not include the impacts of any material non-cash valuation adjustments, regulatory-related charges or credits, reorganizations or restructurings, future changes in laws, regulations or regulatory policies, adjustments made to deferred tax assets and liabilities from changes in forecasted state income tax apportionment and valuation allowances including further corporate tax rate changes in Iowa, changes in credit loss liabilities related to guarantees, pending lawsuits and disputes, settlement charges related to pension and other postretirement benefits plans, federal and state income tax audits and other Internal Revenue Service proceedings, impacts from changes to the authorized return on equity for ATC LLC, or changes in GAAP and tax methods of accounting that may impact the reported results of Alliant Energy.

Earnings Conference Call

A conference call to review the

lnt-20260219000035254100000524850000107832false00003525412026-02-192026-02-190000352541lnt:IplMember2026-02-192026-02-190000352541lnt:WplMember2026-02-192026-02-19

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) February 19, 2026

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

(Former name or former address, if changed since last report.)

This combined Form 8-K is separately filed by Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company.

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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 is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Alliant Energy Corporation - Emerging growth company ☐ Interstate Power and Light Company - Emerging growth company ☐ Wisconsin Power and Light 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 ☐

Item 2.02 Results of Operations and Financial Condition.

On February 19, 2026, Alliant Energy Corporation issued a press release announcing its financial results for the fourth quarter and year ended December 31, 2025. A copy of such press release is furnished as Exhibit 99.1 and is incorporated by reference herein.

Item 9.01 Financial Statements and Exhibits.

(a)Not applicable. (b)Not applicable. (c)Not applicable. (d)Exhibits. The following exhibits are being furnished herewith:

Exhibit NumberDescription (99.1)Alliant Energy Corporation press release dated February 19, 2026

(104)Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrants have duly caused this report to be signed on their behalf by the undersigned hereunto duly authorized.

ALLIANT ENERGY CORPORATION

Date: February 19, 2026By: /s/ Dylan M. Syse

Dylan M. Syse Chief Accounting Officer and Controller

INTERSTATE POWER AND LIGHT COMPANY

Date: February 19, 2026By: /s/ Dylan M. Syse

Dylan M. Syse Chief Accounting Officer and Controller

WISCONSIN POWER AND LIGHT COMPANY

Date: February 19, 2026By: /s/ Dylan M. Syse

Dylan M. Syse Chief Accounting Officer and Controller

lnt-20251106000035254100000524850000107832false00003525412025-11-062025-11-060000352541lnt:IplMember2025-11-062025-11-060000352541lnt:WplMember2025-11-062025-11-06

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported) November 6, 2025

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

(Former name or former address, if changed since last report.)

This combined Form 8-K is separately filed by Alliant Energy Corporation, Interstate Power and Light Company and Wisconsin Power and Light Company.

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

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 is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter). Alliant Energy Corporation - Emerging growth company ☐ Interstate Power and Light Company - Emerging growth company ☐ Wisconsin Power and Light 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 ☐

Item 2.02 Results of Operations and Financial Condition.

On November 6, 2025, Alliant Energy Corporation issued a press release announcing its financial results for the three and nine months ended September 30, 2025. A copy of such press release is furnished as Exhibit 99.1 and is incorporated by reference herein.

Item 9.01 Financial Statements and Exhibits.

(a)Not applicable. (b)Not applicable. (c)Not applicable. (d)Exhibits. The following exhibits are being furnished herewith:

Exhibit NumberDescription (99.1)Alliant Energy Corporation press release dated November 6, 2025

(104)Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrants have duly caused this report to be signed on their behalf by the undersigned hereunto duly authorized.

ALLIANT ENERGY CORPORATION

Date: November 6, 2025By: /s/ Dylan M. Syse

Dylan M. Syse Chief Accounting Officer and Controller

INTERSTATE POWER AND LIGHT COMPANY

Date: November 6, 2025By: /s/ Dylan M. Syse

Dylan M. Syse Chief Accounting Officer and Controller

WISCONSIN POWER AND LIGHT COMPANY

Date: November 6, 2025By: /s/ Dylan M. Syse

Dylan M. Syse Chief Accounting Officer and Controller