What changed in this filing

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Item 1. Business

2025-02-21 compared with 2024-02-16 · 115 added, 125 removed, 356 unchanged (40% of the section changed)

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The primary first tier wholly-owned subsidiaries of Alliant Energy are as follows:

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1) IPL - is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Iowa.

IPL provides utility services to incorporated communities as directed by the IUB and utilizes non-exclusive franchises, which cover the use of public right-of-ways for utility facilities in incorporated communities for a maximum term of 25 years.

IPL provides utility services to incorporated communities as directed by the IUC and utilizes non-exclusive franchises, which cover the use of public right-of-ways for utility facilities in incorporated communities for a maximum term of 25 years.

At December 31, 2024, IPL supplied electric and natural gas service to approximately 500,000 and 230,000 retail customers, respectively, in Iowa.

IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa.

IPL is also engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa.

IPL also sells electricity to wholesale customers in Minnesota (IPL’s related wholesale power agreement expires July 2025), Illinois and Iowa.

IPL is also engaged in the generation and distribution of steam for two customers in Cedar Rapids, Iowa, which are each under contract through 2025 for taking minimum quantities of annual steam usage, with certain conditions, after which IPL expects to exit the steam business.

2) WPL - is a public utility engaged principally in the generation and distribution of electricity and the distribution and transportation of natural gas to retail customers in select markets in Wisconsin.

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WPL also sells electricity to wholesale customers in Wisconsin.

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3) CORPORATE SERVICES - provides administrative services to Alliant Energy, IPL, WPL and AEF.

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ATC Holdco LLC holds an interest in Duke-American Transmission Company, LLC, a joint venture between Duke Energy Corporation and ATC, that owns electric transmission infrastructure in North America.

Corporate Venture Investments - includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help advance the transition towards a cleaner, more sustainable, and inclusive energy future, by identifying and researching innovative technologies and business models within the emerging energy economy.

Corporate Venture Investments - includes various minority ownership interests in regional and national venture funds, including a global coalition of energy companies working together to help identify and research innovative technologies and business models within the emerging energy economy.

Non-utility Wind Farm - includes a 50% cash equity ownership interest in a 225 MW non-utility wind farm located in Oklahoma.

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Refer to Note 9 for additional information on WPL’s Sheboygan Falls Energy Facility lease.

Travero - is a diversified supply chain solutions company, including a short-line rail freight service in Iowa;

Travero - is a supply chain solutions company, including a short-line rail freight service in Iowa;

a Mississippi River barge, rail and truck freight terminal in Illinois;

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and a rail-served warehouse in Iowa.

Development-ready Sites - includes various rail-served and ready-to-build manufacturing and industrial sites throughout Iowa and Wisconsin, with access to various airports, interstate freeways and Alliant Energy’s electric services.

Development-ready Sites - includes various rail-served and ready-to-build manufacturing and industrial sites throughout Alliant Energy’s service territories, with access to various airports and interstate freeways.

INFORMATION RELATING TO ALLIANT ENERGY ON A CONSOLIDATED BASIS

1) HUMAN CAPITAL MANAGEMENT - Alliant Energy’s core purpose is to serve customers and build stronger communities.

We constantly strive to attract, retain and develop a diverse and qualified workforce of high-performing employees, and create and foster an environment of inclusion and belonging for all employees.

We constantly strive to attract, retain and develop a qualified workforce of high-performing employees and foster an environment of high levels of engagement.

Employees - At December 31, 2024, Alliant Energy, IPL and WPL had the following full- and part-time employees:

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All of WPL’s bargaining unit employees are covered by the International Brotherhood of Electrical Workers Local 965 collective bargaining agreement, which expires May 31, 2026.

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Safety - Safety is integral to our company’s culture.

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This leadership provides strong support for sustained growth of both employee and public safety programs and initiatives.

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Public safety is equally important, as we interact with our customers to provide energy to their homes and businesses.

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Total Rewards - Our market-competitive Total Rewards programs are designed to meet the varied and evolving needs of our employees.

Through a variety of health, welfare and compensation programs, we offer employees choice and control, while supporting their financial, physical, and mental well-being.

Tools and resources are provided to employees to help maintain and improve their health.

Short- and long-term incentive plans are designed with a mix of operational and financial metrics that align employees with strategic corporate and social goals.

Through a variety of health, welfare and compensation programs, we offer employees choice and control, and help support their financial, physical, and mental well-being.

We provide tools and resources to employees to help maintain and improve their health.

Short- and long-term incentive plans have a mix of operational and financial metrics that align employees with strategic corporate goals.

In addition to competitive salaries and wages, our Total Rewards programs include:

• competitive short- and long-term incentive compensation;

• a 401(k) savings plan with an employer match;

• a 401(k) savings plan with an employer contribution and employer match;

• healthcare and insurance benefits, including medical, vision, dental, life, short-term disability, and long-term disability insurance;

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• Vacation Donation program;

• Volunteer Grants and Matching Gifts program.

Annually, Alliant Energy awards up to 25 scholarships to children of its current employees and eligible retirees who have achieved excellent records in high school who are pursuing a higher education.

Scholarship award recipients may enroll in any accredited two- or four-year college, university or vocational-technical school in the U.S.

Diversity, Equity, Inclusion and Belonging (DEI&B) - A diverse, equitable and inclusive workplace where everyone feels like they belong is crucial for the success and retention of our employees, to attract future talent and to execute our purpose-driven strategy to serve our customers and build stronger communities.

• Volunteer Grants and a Matching Gifts program.

Annually, Alliant Energy awards up to 25 scholarships to children of its current employees and eligible retirees.

Award recipients have achieved excellent records in high school, are pursuing a higher education, and may enroll in any accredited two- or four-year college, university or vocational-technical school in the U.S.

Employee Engagement - A workplace where everyone feels meaningful connection to work and company goals is crucial for the success and retention of our employees, to attract future talent and to execute our purpose-driven strategy to serve our customers and build stronger communities.

It is one of our Values - “Care for others:

Together we create a workplace where people feel like they belong and can use their unique backgrounds, talents and perspectives to their fullest potential.” Alliant Energy is driven by DEI&B and believes the achievement of its strategic objectives can only be achieved with a focused and engaged workforce.

Alliant Energy’s corporate officers group currently has approximately 44% gender diversity and 25% ethnic diversity.

Our efforts to create a diverse, equitable and inclusive workplace have focused on reducing bias, building diverse teams, and listening to and acting on employee feedback, and include:

• learning opportunities for employees, such as inviting employees to participate in area diversity summits and supporting company-wide listening sessions, speakers and programs;

• Employee Resource Groups that foster a diverse, equitable and inclusive workplace that supports employee well-being while promoting professional development and enhancing community relationships;

• a DEI&B Leadership Team that partners with the Human Resources department and hiring managers to attract more diverse applicants that represent the diversity of the communities we serve.

Our DEI&B initiatives also include a focus on building a diverse Board of Directors.

We believe it is in our shareowners’ best interest to have a diverse Board representing a wide breadth of experiences and perspectives.

Our Board currently has approximately 40% gender diversity and 20% ethnic diversity.

Our 2023 DEI&B accomplishments include:

• received a perfect score on the Corporate Equality Index administered by the Human Rights Campaign Foundation to benchmark LGBTQ+ rights, policies and practices;

• selected for the 2023 Bloomberg Gender-Equality Index;

• held our fourth annual Day of Understanding, with 88% voluntary company-wide participation, where leaders facilitated conversations around creating a culture of inclusion and belonging, helping to ensure employees are seen, heard and valued.

Alliant Energy’s short- and long-term incentive compensation plans include diversity metrics to drive leadership accountability for efforts to advance a diverse and inclusive culture.

Talent Development and Workforce Readiness - We support employees in the growth of their careers through several training opportunities and development programs.

These include tuition reimbursement, and online, instructor-led and on-the-job learning formats, as well as leadership development and succession planning.

Together we create a workplace where people feel like they can use their backgrounds, talents and perspectives to their fullest potential.” Alliant Energy believes the achievement of its strategic objectives can only be achieved with a focused and engaged workforce.

Our efforts to advance employee engagement in our workforce include:

We offer various learning opportunities for employees, such as participating in area summits, supporting company-wide listening sessions, providing training opportunities, and hosting speakers, among other programs, as well as leaders facilitating conversations around employee engagement, helping to ensure employees are seen, heard and valued;

• Listening and responding:

We collect and act upon feedback through employee sentiment surveys;

• Empowering:

We promote and foster an engaged workforce, providing opportunities to collaborate, network, and share their insights and talents;

Our Leadership Team identifies and champions initiatives to help advance a culture that values employee engagement.

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As we attract and introduce a diverse pool of candidates to our industry, we have an early careers program that includes apprenticeships, youth programs (high school) and internships (college).

Talent Development and Workforce Readiness - We support all employees in their skill development and career growth, offering several training opportunities, development programs and tuition reimbursement, as well as leadership development and succession planning.

Development goals and conversations with leadership help identify opportunities to learn through a mix of on-the-job experience, collaboration and formal content to build needed skills for today and the future.

To help attract and introduce a wide range of candidates to our industry, we have early careers programs that include apprenticeships, youth programs (high school) and internships (college).

Our programs provide a pipeline of talented students to engage in meaningful, hands-on work experiences.

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Under the Natural Gas Act, FERC has authority over certain natural gas facilities and operations of IPL and WPL.

IUB - IPL is subject to regulation by the IUB for various matters including, but not limited to, retail utility rates and standards of service, accounting requirements, the construction of EGUs, and the acquisition, sale or lease of assets with values that exceed 3% of IPL’s revenues.

In Iowa, counties and cities are prohibited from regulating the sale of natural gas and propane, which supports IPL’s ability to provide gas utility service to a diversified base of retail customers and industries.

Retail Utility Base Rates - IPL files periodic requests with the IUB for retail rate changes and may base those requests on either historical or forward-looking test periods.

The IUB must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed, subject to certain exceptions.

The historical test periods may be adjusted for certain known and measurable changes to capital investments, cost of capital and operating and maintenance expenses consistent with IUB rules and regulations.

The IUB has rules that establish minimum filing requirements for rate reviews using a forward-looking test period, and a related subsequent proceeding review after the close of the forward-looking test period.

IUC - IPL is subject to regulation by the IUC for various matters including, but not limited to, retail utility rates and standards of service, accounting requirements, the construction of EGUs, and the acquisition, sale or lease of assets with values that exceed 3% of IPL’s revenues.

In Iowa, counties and cities are prohibited from regulating the sale of natural gas and propane, which supports IPL’s ability to provide gas utility service to retail customers and industries.

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Retail Utility Base Rates - IPL files periodic requests with the IUC for retail rate changes and may base those requests on either historical or forward-looking test periods.

The IUC must decide on requests for retail rate changes within 10 months of the date of the application for which changes are filed, subject to certain exceptions.

The IUC has rules that establish minimum filing requirements for rate reviews using a forward-looking test period, and a related subsequent proceeding review after the close of the forward-looking test period.

The rules provide that in the subsequent proceeding review, a utility’s actual costs and revenues will be presumed to be reasonably consistent with the forward-looking test period if the utility’s actual return on common equity falls within a standard of reasonableness of 50 basis points above to 50 basis points below the authorized return on common equity.

If the utility’s actual return on common equity is outside of this range, future rates could be adjusted.

In addition, the rules require that IPL must receive an order from the IUB related to the subsequent proceeding review before it can file another rate review.

Energy Efficiency - In accordance with Iowa law, IPL is required to file an energy efficiency plan (EEP) every five years with the IUB.

In addition, the rules require that IPL must receive an order from the IUC related to the subsequent proceeding review before it can file another rate review.

Also, IPL is required to defer a portion of its earnings if its annual regulatory return on common equity exceeds certain levels.

Refer to “ Rate Matters ” in MDA for discussion of IPL’s retail electric base rate moratorium from October 2025 through September 2029 approved by the IUC in IPL’s most recent retail electric rate review.

Energy Efficiency - In accordance with Iowa law, IPL is required to file an energy efficiency plan (EEP) every five years with the IUC.

An EEP provides a utility’s plan and related budget to achieve specified levels of electric and gas energy savings.

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IUB approval demonstrates that IPL’s EEP is reasonably expected to achieve cost-effective delivery of the energy efficiency programs.

IUC approval demonstrates that IPL’s EEP is reasonably expected to achieve cost-effective delivery of the energy efficiency programs.

Refer to Note 1(g) for discussion of the recovery of these costs from IPL’s retail electric and gas customers.

Electric Generating Units - IPL must obtain a certificate of public convenience, use and necessity (GCU Certificate) from the IUB in order to construct a new, or significantly alter (including fuel switching) an existing, EGU located in Iowa with 25 MW or more of nameplate generating capacity.

IPL’s ownership and operation of EGUs (including those located outside the state of Iowa) to serve Iowa customers is subject to retail utility rate regulation by the IUB.

Gas Pipeline Projects - IPL must obtain a pipeline permit from the IUB related to the siting of utility gas pipelines in Iowa that will be operated at a pressure over 150 pounds per square inch and will transport gas to a distribution system or single, large volume customer.

Advance Rate-making Principles - Iowa law allows Iowa utilities to request rate-making principles prior to making certain generation investments in Iowa.

As a result, IPL may file for, and the IUB must render a decision on, rate-making principles for certain new EGUs located in Iowa, including any alternative energy production facility (such as a wind or solar facility, as well as battery storage constructed in combination with these facilities), combined-cycle natural gas-fired EGU, and certain base-load EGUs with a nameplate generating capacity of 300 MW or more (such as nuclear-fired generation).

Electric Generating Units - IPL must obtain a certificate of public convenience, use and necessity (GCU Certificate) from the IUC in order to construct a new, or significantly alter (including fuel switching) an existing, EGU or energy storage facility located in Iowa with a nameplate generating capacity of 25 MW or more.

IPL’s ownership and operation of EGUs (including those located outside the state of Iowa) to serve Iowa customers is subject to retail utility rate regulation by the IUC.

Gas Pipeline Projects - IPL must obtain a pipeline permit from the IUC related to the siting of utility gas pipelines in Iowa that will be operated at a pressure over 150 pounds per square inch and will transport gas to a distribution system or single, large volume customer.

Advance Rate-making Principles - Iowa law allows Iowa utilities to request rate-making principles prior to making certain investments in Iowa.

As a result, IPL may file for, and the IUC must render a decision on, rate-making principles for certain new EGUs located in Iowa, including any alternate energy production facility (such as a wind, solar, energy storage or nuclear-fired facility), combined-cycle natural gas-fired EGU, and certain base-load EGUs with a nameplate generating capacity of 300 MW or more.

Advance rate-making principles are also available for the repowering of an alternative energy production facility or certain significant alterations of an existing EGU.

Upon approval of rate-making principles by the IUB, IPL must either construct the EGU or repower the alternative energy production facility under the approved rate-making principles, or not at all.

If rate-making principles are not approved by the IUB, IPL may construct the facility, subject to other applicable approvals (such as a GCU Certificate), subject to recovery in future rate reviews.

Electric Generating Unit Environmental Controls Projects - At its sole discretion, IPL may submit an updated emissions plan and budget to the IUB setting out a multi-year plan and budget for managing regulated emissions from its coal-fired EGUs in a cost-effective manner.

Upon approval of rate-making principles by the IUC, IPL must either construct the EGU or repower the alternative energy production facility under the approved rate-making principles, or not at all.

If rate-making principles are not approved by the IUC, IPL may construct the facility, subject to other applicable approvals (such as a GCU Certificate), subject to recovery in future rate reviews.

The IUC’s 2023 order for the advance rate-making principles for IPL’s 400 MW of solar generation projects placed in service in 2024 included a consumer protection plan, which monitors IPL’s achievement of certain aggregate summer capacity factors for those projects during June, July and August each calendar year over 30 years.

Actual three-year rolling average summer capacity factors will be compared to target capacity factors, which may result in surpluses or deficits that would be offset against one another and contribute to an accumulated balance in a given calendar year.

Surpluses or deficits will be capped at $3 million in aggregate per year.

At the end of the program, any accumulated deficit balance would be addressed in IPL’s next rate review, and any accumulated surplus balance would not result in any return to IPL.

Electric Generating Unit Environmental Controls Projects - At its sole discretion, IPL may submit an updated emissions plan and budget to the IUC setting out a multi-year plan and budget for managing regulated emissions from its coal-fired EGUs in a cost-effective manner.

IPL must simultaneously submit this plan and budget to the Iowa Department of Natural Resources for a determination of whether the plan and budget meet state environmental requirements for regulated emissions.

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Currently, WPL is required to defer a portion of its earnings if its annual regulatory return on common equity exceeds certain levels.

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Public Benefits - WPL contributes 1.2% of its annual retail utility revenues to help fund Focus on Energy, Wisconsin’s state-wide energy efficiency and renewable energy resource program.

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Refer to Note 1(g) for discussion of the recovery of these costs from WPL’s retail electric and gas customers.

New Electric Generating Units - A CA application is required to be filed with the PSCW for construction approval of any new EGU (including battery storage) with a capacity of less than 100 MW and a project cost of $12.4 million or more.

WPL must obtain a CPCN from the PSCW in order to construct a new EGU in Wisconsin with a capacity of 100 MW or more.

New Electric Generating Units - A CA application is required to be filed with the PSCW for construction approval of any new EGU (including energy storage) with a capacity of less than 100 MW and a project cost of $16.3 million or more.

WPL must obtain a CPCN from the PSCW in order to construct a new EGU (including energy storage) in Wisconsin with a capacity of 100 MW or more.

In addition, WPL’s ownership and operation of EGUs (including those located outside the state of Wisconsin) to serve Wisconsin customers are subject to retail utility rate regulation by the PSCW.

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Advance Rate-making Principles - Wisconsin law provides Wisconsin utilities with the opportunity to request rate-making principles prior to the purchase or construction of any EGU utilized to serve Wisconsin customers.

WPL is not obligated to file

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for or accept authorized rate-making principles under Wisconsin law.

WPL is not obligated to file for or accept authorized rate-making principles under Wisconsin law.

WPL can proceed with an approved project under traditional rate-making terms or accept authorized rate-making principles under Wisconsin law.

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In 2009, the EPA issued a ruling that found GHG emissions contribute to climate change and therefore threaten public health and welfare, which is the basis for implementing CO2 reduction standards under the CAA.

While the EPA’s rules to regulate GHG issued under the authority of the CAA remain subject to further review, growing emphasis on climate change and evolving energy technologies are driving efforts to decarbonize the environment through voluntary emissions reductions.

The primary GHG directly emitted from Alliant Energy’s utility operations is CO2 from the combustion of fossil fuels at its EGUs.

Clean Air Act Section 111(d) - In 2015, the EPA issued the Clean Power Plan rule under Section 111(d) of the CAA to reduce CO2 emissions from existing fossil-fueled EGUs through broad electricity system-wide measures.

This was replaced by the Affordable Clean Energy rule in 2019, to reduce CO2 emissions from existing coal-fired EGUs through heat rate improvements.

In 2021, the U.S.

Court of Appeals for the District of Columbia vacated and remanded the Affordable Clean Energy rule to the EPA for reconsideration.

In 2022, the Supreme Court issued a decision limiting the extent of the EPA’s authority under Section 111(d) to emissions reduction technologies and operational improvements.

In May 2023, the EPA proposed the revised Section 111(d) rule, which would establish emission guidelines for states to implement Best System of Emission Reduction standards for GHG emissions from existing fossil-fueled EGUs and certain combustion turbines.

The proposed requirements would be phased in beginning in 2030.

The EPA also proposed to repeal the Affordable Clean Energy rule.

The EPA’s proposed revised Section 111(d) rule would require states to implement plans to reduce CO2 emissions through various Best System of Emission Reduction standards by applying various measures at affected sources, including retirement, enforceable limits on operational capacity, co-firing with low-GHG fuels, or other technological controls.

State plans must be submitted within 24 months of the final rule’s effective date and are subject to EPA approval.

The proposed standards could impact IPL’s coal-fired Ottumwa Generating Station, George Neal Generating Station, Prairie Creek Generating Station Unit 3 and Louisa Generating Station, and IPL’s natural gas-fired Burlington Generating Station and Prairie Creek Generating Station Unit 4.

In addition, the proposed standards could impact natural gas-fired combustion turbines with a capacity of 300 MW or more, including IPL’s Marshalltown Generating Station and Emery Generating Station, and WPL’s Riverside Energy Center and West Riverside Energy Center.

The proposed standards are currently not expected to impact WPL’s coal-fired Columbia Energy Center or Edgewater Generating Station given current plans to retire these EGUs prior to the proposed 2030 implementation deadline.

The EPA plans to finalize the revised Section 111(d) rule in 2024.

Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these matters.

Clean Air Act Section 111(b) - In 2015, the EPA published final standards under Section 111(b) of the CAA, which establish CO2 emissions limits for certain new fossil-fueled EGUs.

In May 2023, the EPA proposed revised standards under Section 111(b), which would establish CO2 emissions limits from certain new and reconstructed fossil-fueled EGUs and would apply prospectively.

IPL’s Marshalltown Generating Station and WPL’s West Riverside Energy Center are currently subject to the EPA’s Section 111(b) regulation and thus would be impacted by these revised standards.

The EPA plans to finalize the revised Section 111(b) rule in 2024.

Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these standards.

Clean Air Act Section 111(d) - In May 2024, the EPA enacted the final Section 111(d) rule under the CAA for certain fossil-fueled EGUs, which requires states to implement plans to reduce CO2 emissions through various Best System of Emission Reduction (BSER) measures at affected sources, including retirement, enforceable limits on operational capacity, co-firing with low-GHG fuels, or carbon capture and energy storage technology.

State plans are subject to EPA approval, and must be submitted by May 2026.

The final rule’s compliance requirements will be phased in beginning in 2030 and covers fossil-fueled EGUs that utilize steam boilers to generate electricity, including IPL’s coal-fired Ottumwa Generating Station, George Neal Generating Station, Prairie Creek Generating Station Unit 3 and Louisa Generating Station, WPL’s coal-fired Edgewater Generating Station Unit 5 (WPL currently plans to convert Edgewater Unit 5 to natural gas in 2028, subject to regulatory approvals), and IPL’s natural gas-fired Burlington Generating Station and Prairie Creek Generating Station Unit 4.

The final rule does not apply to EGUs that are retired by January 2032.

If WPL’s coal-fired Columbia Energy Center is retired by the end of 2029, the final rule would not be applicable;

however, if WPL converts Columbia Unit 1 and/or Unit 2 to natural gas, then the final rule would be applicable for the EGUs that are converted.

In addition, the final rule does not impact existing natural gas-fired combustion turbines, including IPL’s Marshalltown Generating Station and Emery Generating Station, and WPL’s Riverside Energy Center and West Riverside Energy Center;

however, these EGUs could be subject to future Section 111(d) rules to reduce CO2 emissions from existing combustion turbines.

Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these matters, including resolution of ongoing litigation.

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Clean Air Act Section 111(b) - In 2015, the EPA published final standards under Section 111(b) of the CAA, which establish CO2 emissions limits for certain new fossil-fueled EGUs, including IPL’s Marshalltown Generation Station and WPL’s West Riverside Energy Center.

In addition, in May 2024, the EPA enacted final revised standards under Section 111(b), which establish CO2 emissions limits from certain new and reconstructed fossil-fueled EGU combustion turbines that commenced operation after May 23, 2023 with a capacity greater than 25 MW.

The final revised standards do not apply to IPL’s and WPL’s current fossil-fueled EGU combustion turbines since they were all placed into service before May 23, 2023 and have not been reconstructed since that date.

Alliant Energy, IPL and WPL are currently unable to predict with certainty the future outcome or impact of these revised standards, including resolution of ongoing litigation.

Cross-State Air Pollution Rule - CSAPR is a regional sulfur dioxide and nitrogen oxides cap-and-trade program, where compliance with emission limits may be achieved by purchasing emission allowances and/or reducing emissions through changes in operations or the additions of environmental controls.

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In 2023, the EPA finalized revisions to the CSAPR state-specific ozone season nitrogen oxides emission caps and utility-specific emission allowances for certain states, including Wisconsin, beginning in 2023;

WPL currently receives, and expects to receive in the future, enough CSAPR emission allowances to ensure ongoing compliance without the need to purchase additional allowances.

The 2023 CSAPR revisions do not currently apply to Iowa;

however, Iowa

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could be included in a future rule.

As a result, Alliant Energy and IPL are currently unable to predict with certainty the future outcome or impact of these matters.

however, these revisions were stayed by the Supreme Court in June 2024.

In November 2024, the EPA issued an interim final rule to stay the 2023 rule and re-establish the prior emission caps and allowance allocations, including Wisconsin, pending judicial review.

WPL currently receives, and expects to receive in the future, enough CSAPR emission allowances to ensure ongoing compliance without the need to purchase additional allowances or materially curtail operations.

These revisions do not currently apply to Iowa;

however, Iowa could be included in a future rule.

As a result, Alliant Energy and IPL are currently unable to predict with certainty the future outcome or impacts of these matters.

New Source Performance Standards (NSPS) for Combustion Turbines - The EPA establishes requirements under the CAA for various categories of stationary sources that cause or contribute significantly to air pollution, and may reasonably be anticipated to endanger public health or welfare, which are referred to as NSPS.

These standards reflect the degree of emission limitation achievable through the application of the BSER.

In December 2024, the EPA proposed updates to the NSPS for combustion turbines built, reconstructed, or modified after December 13, 2024, which would establish more stringent emission limits for nitrogen oxides emissions and retain the current sulfur dioxide emission limits.

This proposal would establish size-based subcategories for new, reconstructed or modified combustion turbines, and could require combustion controls or selective catalytic reduction control equipment.

Alliant Energy, IPL and WPL are currently evaluating the proposed rule and are unable to predict with certainty future compliance impacts;

however, costs to comply with this rule could have a material impact on their financial condition and results of operations.

Water Quality -

Effluent Limitation Guidelines - In 2015, the EPA published final effluent limitation guidelines that required changes to discharge limits for wastewater from certain IPL and WPL steam EGUs.

In 2020, revised effluent limitation guidelines (2020 Reconsideration Rule) became effective, which incorporated flexibility to the 2015 rule, including a new subcategory for coal-fired EGUs that will be retired or converted to no longer burn coal before 2028.

In 2021, the current Presidential Administration issued an Executive Order requiring the review and possible revision of environmental regulations issued during the prior Administration.

As a result, in March 2023, the EPA published a proposed supplemental rule (2023 Supplemental Rule) to revise the guidelines for steam-electric generating facilities.

The 2023 Supplemental Rule proposes to tighten some of the flexibility offered in the 2020 Reconsideration Rule for certain waste streams, while additionally proposing a newly defined legacy wastewater waste stream.

The 2020 Reconsideration Rule will remain in effect while the 2023 Supplemental Rule continues through the rule-making process.

Compliance with the 2023 Supplemental Rule will be determined by each facility’s wastewater discharge permit, and new or revised limits would become effective as soon as possible but no later than December 31, 2029.

Alliant Energy, IPL and WPL are currently evaluating the 2023 Supplemental Rule and are unable to predict with certainty future compliance impacts.

Effluent Limitation Guidelines - In May 2024, the EPA enacted a final rule that revises discharge limits for specific categories of wastewater from existing steam EGUs.

The new limitations will be implemented in each facility’s wastewater discharge permits issued by state agencies and become effective as soon as possible but no later than December 31, 2029.

Alliant Energy, IPL and WPL are currently evaluating the final rule and are unable to predict with certainty future compliance impacts, including resolution of ongoing litigation;

however, costs to comply with this rule could have a material impact on their financial condition and results of operations.

Land and Solid Waste -

Coal Combustion Residuals Rule - The CCR Rule, which became effective in 2015, regulates CCR as a non-hazardous waste.

IPL and WPL have coal-fired EGUs with coal ash ponds and active CCR landfills that are impacted by this rule.

In May 2023, the EPA published proposed amendments to the CCR Rule that would expand the scope of regulation to include coal ash ponds at sites that no longer produce electricity and inactive landfills, including some IPL and WPL facilities.

Alliant Energy, IPL and WPL are currently evaluating the proposed 2023 CCR Rule amendments and are unable to predict with certainty the future outcome or impact of these updates.

Coal Combustion Residuals Rule - The CCR Rule, which initially became effective in 2015, regulates CCR as a non-hazardous waste.

In May 2024, the EPA revised the CCR Rule, which significantly expands the scope of regulation, and as discussed in Note 1 3 , Alliant Energy, IPL and WPL recorded additional AROs in 2024.

IPL and WPL have coal ash ponds at current and former EGU sites, and active and inactive CCR landfills, that are impacted by this rule.

Alliant Energy, IPL and WPL continue to evaluate the revised CCR Rule and are unable to predict with certainty the future outcome or impact of these updates, including resolution of ongoing litigation.

Manufactured Gas Plant Sites - Refer to Note 1 6 (e) for discussion of IPL’s and WPL’s MGP sites.

Renewable Energy Standards - Iowa and Wisconsin have renewable energy standards, which establish the minimum amount of energy IPL and WPL must supply from renewable resources.

IPL primarily relies upon renewable energy generated from the wind resources it owns and renewable energy acquired under PPAs to meet these requirements.

IPL primarily relies upon renewable energy generated from the wind or solar resources it owns and renewable energy acquired under PPAs to meet these requirements.

WPL utilizes its current renewable portfolio, which primarily consists of wind, solar and hydro energy, both owned and acquired under PPAs, to meet these requirements.

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3) STRATEGY - Refer to “ Overview ” in MDA for discussion of Alliant Energy’s strategy, which supports its mission to deliver energy solutions and exceptional service that its customers and communities count on - affordably, safely, reliably and sustainably.

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INFORMATION RELATING TO UTILITY OPERATIONS

Alliant Energy’s utility business (IPL and WPL) has three segments:

a) electric operations;

b) gas operations;

and c) other, which includes IPL’s steam operations and the unallocated portions of the utility business.

Alliant Energy’s utility business includes the operations of IPL (electric, gas and steam operations) and WPL (electric and gas operations), which are both reportable segments.

IPL’s and WPL’s electric, gas and other revenues as a percentage of total revenues were as follows:

1) ELECTRIC UTILITY OPERATIONS

General - Electric utility operations represent the largest operating segment for Alliant Energy, IPL and WPL.

Alliant Energy’s electric utility operations are located in the Midwest with IPL providing retail electric service in Iowa and WPL providing retail and wholesale electric service in Wisconsin.

IPL also sells electricity to wholesale customers in Minnesota, Illinois and Iowa.

General - Alliant Energy’s electric utility operations are located in the Midwest with IPL providing retail and wholesale electric service in Iowa and WPL providing retail and wholesale electric service in Wisconsin.

IPL also sells electricity to wholesale customers in Minnesota and Illinois.

Refer to the “ Electric Operating Information ” tables for additional details regarding electric utility operations.

Customers - IPL and WPL provide electric utility service to a diversified base of retail customers in several industries, with the largest concentrations in the farming, agriculture, industrial manufacturing, chemical (including ethanol), packaging and food

Table of C o ntents

Customers - IPL and WPL provide electric utility service to a large base of retail customers in several industries, with the largest concentrations in the farming, agriculture, industrial manufacturing, chemical (including ethanol), packaging and food industries.

IPL and WPL also sell electricity to wholesale customers, which primarily consist of municipalities and rural electric cooperatives.

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Electric Supply - Alliant Energy, IPL and WPL have met, and expect to continue meeting, customer demand of electricity through a mix of electric supply, including owned EGUs, PPAs and additional purchases from wholesale energy markets.

Alliant Energy expects its mix of electric supply to change in the next several years with its planned transition away from coal-fired EGUs by considering additional renewable energy such as solar generation, battery storage, repowering of existing wind farms and distributed energy resources, including community solar and small-scale energy storage systems, dispatchable gas generation projects, and potential sales of partial interests in West Riverside to neighboring utilities.

Long-term generation plans are intended to meet customer demand, reduce air emissions and water impacts, reduce reliance on wholesale market purchases and mitigate the impacts of future EGU retirements while maintaining compliance with long-term electric demand planning reserve margins, renewable energy standards established by regulators and other various requirements.

Electric Demand Planning Reserve Margin - IPL and WPL are required to maintain a planning reserve margin above their load at the time of the MISO-wide peak to ensure reliability of electric service to their customers.

Alliant Energy expects its current mix of electric supply to continue to evolve with new wind and solar generation, energy storage facilities, new natural gas resources, refurbishing of existing wind farms, improvements at existing natural gas-fired EGUs and converting certain coal-fired EGUs to natural gas.

Long-term generation plans are intended to meet growing customer demand, reduce air emissions and water impacts, reduce reliance on wholesale market purchases and mitigate the impacts of future EGU retirements while maintaining compliance with long-term electric demand planning reserve margins, renewable energy standards established by regulators, among other requirements.

Electric Demand Planning Reserve Margin - IPL and WPL are required to maintain a planning reserve margin above their load at the time of the MISO-wide peak each season to ensure reliable electric service to their customers.

IPL and WPL utilize accredited capacity from EGUs they own, and have rights to through PPAs, to meet a substantial portion of their current MISO planning reserve margin requirements and periodically rely on short-term market capacity purchases to supplement the accredited capacity from such EGUs.

MISO Seasonal Resource Adequacy Process - In 2022, FERC approved MISO’s proposal to change its resource adequacy process establishing capacity planning reserve margin and capacity accreditation requirements effective with the June 1, 2023 through May 31, 2024 MISO Planning Year, to help ensure the reliability of electricity in the MISO region.

The process changed from a Summer-based annual construct to four distinct seasons.

FERC’s approval also established planning reserve margin requirements for all market participants on a seasonal basis and determined a seasonal accredited capacity value for certain classes of generating resources, including higher accredited capacity for wind generation during the Spring, Fall and Winter seasons and higher accredited capacity for solar generation during the Summer season.

Alliant Energy, IPL and WPL currently plan to construct and/or acquire additional renewable, battery and natural gas resources to meet the requirements of the seasonal resource adequacy process and have reflected the estimated capital expenditures for these projects in the “Generation” lines in the construction and acquisition table in “ Liquidity and Capital Resources .” Seasonal capacity reserve margins are as follows:

Table of C o ntents

MISO Seasonal Resource Adequacy Process - MISO’s resource adequacy process includes capacity planning reserve margins and capacity accreditation requirements with four distinct seasons, to help ensure the reliability of electricity in the MISO region.

Capacity planning reserve margins are required for all market participants on a seasonal basis, and seasonal accredited capacity values are determined for certain classes of generating resources, including higher accredited capacity for wind generation during the Spring, Fall and Winter seasons and higher accredited capacity for solar generation during the Summer season.

Beginning with the June 1, 2028 through May 31, 2029 planning period, MISO will implement a Direct Loss of Load methodology to determine capacity accreditation, which will incorporate forward-looking analysis, and historical resource-specific performance during periods of high system risk over the previous three years.

Alliant Energy, IPL and WPL currently plan to construct and/or acquire additional renewable, energy storage and natural gas resources to meet the requirements of the seasonal resource adequacy process and have reflected the estimated capital expenditures for these projects in the “Generation” lines in the construction and acquisition table in “ Liquidity and Capital Resources .” Seasonal capacity reserve margins are as follows:

June 2025 - August 2025

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Required unforced capacity reserve margin 7.9% 14.9% 18.4% 25.3%

Generation Fuel Supply - IPL and WPL own a portfolio of EGUs located in Iowa, Wisconsin and Minnesota with a diversified fuel mix that includes natural gas, renewable resources and coal.

Generation Fuel Supply - IPL and WPL own a portfolio of EGUs located in Iowa, Wisconsin and Minnesota with a fuel mix that includes natural gas, renewable resources and coal.

Refer to “ Properties ” in Item 2 for details of IPL’s and WPL’s EGUs.

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(a) The average cost of natural gas includes commodity and transportation costs, as well as realized gains and losses from swap and option contracts used to hedge the price of natural gas volumes expected to be used by IPL’s and WPL’s natural gas-fired EGUs.

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Natural Gas - Alliant Energy, IPL and WPL own several natural gas-fired EGUs, and WPL also has exclusive rights to the output of AEF’s Sheboygan Falls Energy Facility under an affiliated lease agreement.

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Alliant Energy, IPL and WPL believe they are reasonably insulated against coal price volatility given their current coal procurement process, the specific coal market in their primary purchase region and regulatory cost-recovery mechanisms.

The coal procurement process supports periodic purchases, staggering of contract terms, stair-stepped levels of supply going forward and supplier diversity.

The coal procurement process supports periodic purchases, staggering of contract terms, stair-stepped levels of supply going forward and different suppliers.

Similarly, given the term lengths of their transportation agreements and strategic alignment of agreement expirations for negotiation purposes, Alliant Energy, IPL and WPL believe they are reasonably insulated against future higher coal transportation rates from the major railroads.

Purchased Power - IPL and WPL periodically enter into PPAs and purchase electricity from wholesale energy markets to meet a portion of their customer demand for electricity.

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Electric Transmission - IPL and WPL do not own electric transmission service assets and currently receive transmission services from ITC and ATC, respectively.

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Refer to Note 1(g) for discussion of a transmission cost rider utilized by IPL for recovery of its electric transmission service expense, and discussion of WPL’s escrow for recovery of electric transmission service expense, which is recovered from its retail electric customers through changes in base rates determined during periodic rate proceedings.

Refer to Note 17(g) for discussion of a court decision, which is currently expected to reduce the base return on equity authorized for MISO transmission owners, including ATC.

Refer to Note 1 6 (g) for discussion of a court case and resulting FERC order, which decreased the base return on equity authorized for MISO transmission owners, including ATC.

MISO Markets - IPL and WPL are members of MISO, a FERC-approved Regional Transmission Organization, which is responsible for monitoring and ensuring equal access to the transmission system in their footprint.

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The allocated auction revenue rights are used by IPL and WPL to acquire FTRs through the FTR auctions operated by MISO.

Table of C o ntents

Resource Adequacy - MISO has resource adequacy requirements to help ensure adequate resources to meet forecasted peak load obligations plus a reserve margin.

Only accredited capacity assigned to EGUs is available to meet these requirements.

Accredited capacity assigned to EGUs is available to meet these requirements.

In order for an EGU to receive accredited capacity, it must meet MISO capacity accreditation requirements, which can include satisfying transmission requirements identified in its interconnection agreement prior to the MISO planning year.

Refer to “ Electric Demand Planning Reserve Margin ” above for discussion of MISO’s seasonal resource adequacy process establishing capacity planning reserve margin and capacity accreditation requirements.

Table of C o ntents

Electric Operating Information - Alliant Energy 2024 2023 2022

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2) GAS UTILITY OPERATIONS

General - Gas utility operations represent the second largest operating segment for Alliant Energy, IPL and WPL.

Alliant Energy’s gas utility operations are located in the Midwest with IPL providing gas service in Iowa and WPL providing gas service in Wisconsin.

General - Alliant Energy’s gas utility operations are located in the Midwest with IPL providing gas service in Iowa and WPL providing gas service in Wisconsin.

Refer to the “ Gas Operating Information ” tables for additional details regarding gas utility operations.

Refer to Note 1(g) for information relating to utility natural gas cost recovery mechanisms and Note 1 6 (b) for discussion of natural gas commitments.

Customers - IPL and WPL provide gas utility service to a diversified base of retail customers and industries, including research, education, hospitality, manufacturing and chemicals (including ethanol).

Customers - IPL and WPL provide gas utility service to a large base of retail customers and industries, including research, education, hospitality, manufacturing and chemicals (including ethanol).

In addition, IPL and WPL provide transportation service to commercial and industrial customers by moving customer-owned gas through Alliant Energy’s distribution systems to the customers’ meters.

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Gas Supply - IPL and WPL maintain purchase agreements with numerous suppliers of natural gas from various gas producing regions of the U.S.

In providing gas commodity service to retail customers, Corporate Services administers a diversified portfolio of transportation and storage contracts on behalf of IPL and WPL.

In providing gas commodity service to retail customers, Corporate Services administers a portfolio of transportation and storage contracts on behalf of IPL and WPL.

The tariffs for IPL’s and WPL’s retail gas customers provide for subsequent adjustments to their rates for the cost of gas sold to these customers.

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Normal degree days are calculated using a rolling 20-year average of historical heating degree days.

3) OTHER UTILITY OPERATIONS - STEAM - IPL’s Prairie Creek facility is the primary source of steam for IPL’s two high-pressure steam customers in Iowa.

These customers are each under contract through 2025 for taking minimum quantities of annual steam usage, with certain conditions.

3) OTHER UTILITY OPERATIONS - STEAM - IPL’s Prairie Creek facility provides steam for IPL’s two high-pressure steam customers in Iowa.

These customers are each under contract through 2025 for taking minimum quantities of annual steam usage, with certain conditions, after which IPL currently expects to exit the steam business.

Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 1. Business