AMEREN CORP (AEE) Business

ITEM 1. BUSINESS

GENERAL

Ameren, formed in 1997 and headquartered in St. Louis, Missouri, is a public utility holding company whose primary assets are its equity interests in its subsidiaries. Ameren’s subsidiaries are separate, independent legal entities with separate businesses, assets, and liabilities. Dividends on Ameren’s common stock and the payment of expenses by Ameren depend on distributions made to it by its subsidiaries.

Below is a summary description of Ameren’s principal subsidiaries – Ameren Missouri, Ameren Illinois, and ATXI. Ameren also has other subsidiaries that conduct other activities, such as providing shared services. A more detailed description can be found in Note 1 – Summary of Significant Accounting Policies under Part II, Item 8, of this report.

•Ameren Missouri operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri.

•Ameren Illinois operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois.

•ATXI operates a FERC rate-regulated electric transmission business in the MISO.

For additional information about the development of our businesses, our business operations, and factors affecting our results of operations, financial position, and liquidity, see Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, and Note 1 – Summary of Significant Accounting Policies and Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

BUSINESS SEGMENTS

Ameren has four segments: Ameren Missouri, Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Transmission. The Ameren Missouri segment includes all of the operations of Ameren Missouri. Ameren Illinois Electric Distribution consists of the electric distribution business of Ameren Illinois. Ameren Illinois Natural Gas consists of the natural gas business of Ameren Illinois. Ameren Transmission primarily consists of the aggregated electric transmission businesses of Ameren Illinois and ATXI.

Ameren Missouri has one segment. Ameren Illinois has three segments: Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Illinois Transmission.

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An illustration of the Ameren Companies’ reporting structures is provided below:

(a)    Ameren Missouri consolidates AMF, which is wholly owned by Ameren Missouri.

(b)    Through 2025, the Ameren Transmission segment also included allocated Ameren (parent) interest charges, as well as other subsidiaries engaged in electric transmission project development and investment.

RATES AND REGULATION

Rates

The rates that Ameren Missouri, Ameren Illinois, and ATXI are allowed to charge for their utility services significantly influence the results of operations, financial position, and liquidity of these companies and Ameren. The electric and natural gas utility industry is highly regulated. The utility rates charged to customers are determined by governmental entities, including the MoPSC, the ICC, and the FERC. Decisions by these entities are influenced by many factors, including the cost of providing service, the prudency of expenditures, the quality of service, regulatory staff knowledge and experience, customer intervention, and economic conditions, as well as social and political views. Decisions made by these governmental entities regarding customer rates are largely outside of our control. These decisions, as well as the regulatory lag involved in the process of obtaining approval for new customer rates, could have a material adverse effect on the results of operations, financial position, and liquidity of the Ameren Companies. The extent of the regulatory lag varies for each of Ameren’s electric and natural gas jurisdictions, with the Ameren Transmission business experiencing the least amount of regulatory lag. Depending on the jurisdiction, the effects of regulatory lag are mitigated by various means, including annual revenue requirement reconciliations, the decoupling of revenues from sales volumes to ensure revenues approved in a regulatory rate review are not affected by changes in sales volumes, the recovery of certain capital investments between traditional regulatory rate reviews, the level and timing of expenditures, the use of future test years to establish customer rates, and the use of trackers and riders.

The MoPSC regulates rates and other matters for Ameren Missouri. The ICC regulates rates and other matters for Ameren Illinois. The MoPSC and the ICC regulate non-rate utility matters for ATXI. ATXI does not have retail distribution customers; therefore, the MoPSC and the ICC do not have authority to regulate ATXI’s rates. The FERC regulates Ameren Missouri’s, Ameren Illinois’, and ATXI’s cost-based rates for the wholesale transmission and distribution of energy in interstate commerce and various other matters discussed below under General Regulatory Matters.

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The following table summarizes the key terms of the rate orders in effect for customer billings for each of Ameren’s utilities as of January 1, 2026, except as noted:

(a)Includes pass-through costs recovered from customers, such as purchased power for electric distribution delivery service and natural gas purchased for resale for natural gas delivery service, and intercompany eliminations.

(b)Ameren Missouri’s electric generation, transmission, and delivery service rates are bundled together and charged to retail customers under a combined electric service rate. Because the bundled rates charged to MoPSC retail customers include the revenue requirement associated with Ameren Missouri's FERC-regulated transmission services, the table above does not separately reflect a FERC-authorized rate base or allowed ROE.

(c)This rate order did not specify an ROE, capital structure, or rate base.

(d)In December 2024, the ICC approved an average annual rate base for 2024, 2025, 2026, and 2027 of $4.2 billion, $4.4 billion, $4.6 billion, and $4.8 billion, respectively. Under the MYRP, Ameren Illinois reconciles its actual revenue requirement, as adjusted for certain cost variations, to ICC-approved electric distribution service rates on an annual basis, subject to a reconciliation cap. The reconciliation cap limits the annual adjustment to 105% of the annual revenue requirement approved by the ICC. In December 2025, the ICC approved a year end rate base for 2024 of $4.2 billion. Rate changes consistent with the December 2025 reconciliation order became effective in January 2026.

(e)Ameren Illinois electric energy-efficiency investment rates are updated annually and become effective each January. Under current Illinois law, the ROE component of the applicable WACC is based on the annual average of the monthly yields of the 30-year United States Treasury bonds plus 580 basis points and any performance-related basis-point adjustments. Pursuant to the CRGA, beginning in 2027, the ROE component of the applicable WACC for a given year will be that year’s ICC-approved ROE for Ameren Illinois’ electric distribution service. Under current Illinois law and the CRGA, the allowed ROE on electric energy-efficiency investments can be increased or decreased by up to 200 basis points, depending on the achievement of annual energy savings and demand goals.

(f)This rate order was based on a 2026 future test year.

(g)Transmission rates are updated annually and become effective each January. They are determined by a company-specific, forward-looking formula ratemaking framework based on each year’s forecasted information. The 10.48% return, which includes a 50-basis-point incentive adder for participation in an RTO, is based on the FERC’s October 2024 order.

For additional information on Ameren Missouri, Ameren Illinois, and ATXI rate matters, see Results of Operations and Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, Quantitative and Qualitative Disclosures About Market Risk under Part II, Item 7A, and Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

General Regulatory Matters

Ameren Missouri, Ameren Illinois, and ATXI must receive FERC approval to enter into various transactions, such as issuing short-term debt securities and conducting certain acquisitions, mergers, and consolidations. In addition, Ameren Missouri, Ameren Illinois, and ATXI must receive authorization from the applicable state public utility regulatory agency to issue stock and long-term debt securities and to conduct mergers, affiliate transactions, and various other activities.

Ameren Missouri, Ameren Illinois, and ATXI are also subject to mandatory reliability standards, including cybersecurity standards adopted by the FERC, to ensure the reliability of the bulk electric power system. These standards are developed and enforced by the NERC, pursuant to authority delegated to it by the FERC. Ameren Missouri, Ameren Illinois, and ATXI are members of the SERC. The SERC is one of six regional entities and represents all or portions of 16 central and southeastern states under authority from the NERC. Ameren Missouri is also a member of the MRO, which is also one of the six regional entities and represents all or portions of 16 central, southern, and midwestern states, as well as two Canadian provinces, under authority from the NERC. The regional entities of the NERC implement and enforce reliability standards approved by the FERC to safeguard the reliability of the bulk power systems throughout North America. If any of Ameren Missouri, Ameren Illinois, or ATXI is found not to be in compliance with these mandatory reliability standards, it could incur substantial monetary penalties and other sanctions.

Under the Public Utility Holding Company Act of 2005, the FERC and the state public utility regulatory agencies in each state Ameren and its subsidiaries operate in may access books and records of Ameren and its subsidiaries that are found to be relevant to costs incurred by Ameren’s rate-regulated subsidiaries that may affect jurisdictional rates. The act also permits the MoPSC and the ICC to request that the FERC review cost allocations by Ameren Services to other Ameren subsidiaries.

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Operation of Ameren Missouri’s Callaway Energy Center is subject to regulation by the NRC. The license for the Callaway Energy Center is currently set to expire in 2044. Ameren Missouri’s hydroelectric Osage Energy Center and pumped-storage hydroelectric Taum Sauk Energy Center, as licensed projects under the Federal Power Act, are subject to FERC regulations affecting, among other aspects, the general operation and maintenance of the projects. The licenses for the Osage Energy Center and the Taum Sauk Energy Center expire in 2047 and 2044, respectively. Ameren Missouri’s Keokuk Energy Center and its dam on the Mississippi River between Hamilton, Illinois, and Keokuk, Iowa, are operated under authority granted by an Act of Congress in 1905. The Keokuk Energy Center dam safety program is regulated by the Illinois Department of Natural Resources.

For additional information on regulatory matters, see Note 2 – Rate and Regulatory Matters, Note 9 – Callaway Energy Center, and Note 14 – Commitments and Contingencies under Part II, Item 8, of this report.

Environmental Matters

Our electric generation, transmission, and distribution and natural gas distribution and storage operations must comply with a variety of statutes and regulations relating to the protection of the environment and human health and safety, including permitting programs implemented by federal, state, and local authorities. Such environmental laws regulate air emissions; protect water bodies; regulate the handling and disposal of hazardous substances and waste materials; establish siting and land use requirements; and protect against ecological impacts. Federal and state authorities periodically review and modify existing regulations and adopt new regulations, which may impact our planning process and the ultimate implementation of these or other new or revised regulations. Executive orders issued by the presidential administration as well as local and state land use requirements can also impact our planning activities.

For discussion of environmental matters, including NOx and SO2 emission reduction requirements, regulation of CO2 emissions, wastewater discharge standards, remediation efforts, and CCR management regulations, see Note 14 – Commitments and Contingencies under Part II, Item 8, of this report.

TRANSMISSION

Ameren owns an integrated transmission system that is composed of the transmission assets of Ameren Missouri, Ameren Illinois, and ATXI. Ameren also operates two MISO balancing authority areas: AMMO and AMIL. The AMMO balancing authority area includes the load and most energy centers of Ameren Missouri, and had a peak demand of 7,487 MWs in 2025. The AMIL balancing authority area includes the load of Ameren Illinois and certain Ameren Missouri energy centers located in Illinois, and had a peak demand of 8,027 MWs in 2025. The Ameren transmission system directly connects with 15 other balancing authority areas for the exchange of electric energy.

Ameren Missouri, Ameren Illinois, and ATXI are transmission-owning members of the MISO. Ameren Missouri is authorized by the MoPSC to participate in the MISO for an indefinite term, subject to the MoPSC’s authority to require future proceedings if an event or circumstance occurs that significantly affects Ameren Missouri’s position in the MISO. Ameren Illinois’ election to participate in the MISO is subject to the ICC’s oversight. The CRGA requires the ICC and IPA to conduct a study to examine the costs and benefits of establishing a single, state-specific RTO, consolidating Illinois utilities’ RTO membership into one existing RTO, or maintaining the existing RTO membership structure. Additional studies may be required or requested by the Illinois legislature. The ICC and IPA must publish the study by December 2026.

SUPPLY OF ELECTRIC POWER

Capacity

Ameren Missouri offers for sale all of its capacity to the MISO and purchases the capacity it needs to supply its native load sales from the MISO. Ameren Illinois purchases all of its capacity from the MISO and hedges those purchases through bilateral contracts resulting from IPA procurement events. MISO auctions establish capacity for four seasonal peak load forecasts and are designed to cover each season’s peak demand plus a target reserve margin.

Ameren Missouri

Ameren Missouri’s electric supply is primarily generated from its energy centers. Factors that could cause Ameren Missouri to purchase power include, among other things, energy center outages, the fulfillment of renewable energy requirements, extreme weather conditions, the availability of power at a cost lower than its generation cost, and the lack of sufficient owned generation availability.

Ameren Missouri files a long-term nonbinding preferred resource plan with the MoPSC every three years. Ameren Missouri filed a notice of change in its September 2023 preferred resource plan with the MoPSC in February 2025 to address new load growth opportunities resulting from entities in various industries, including data center and manufacturing, that are considering either locating or expanding their operations within Ameren Missouri’s service territory. The 2025 Change to the 2023 PRP includes, among other things, the following:

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•estimated total load growth of 1.5 gigawatts by 2032 and 2.5 gigawatts by 2040;

•adding 1,600 MWs of natural gas-fired simple-cycle generation by 2030, which will be achieved through the natural gas generation projects discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report, and an additional 1,200 MWs by 2043;

•adding 2,100 MWs of natural gas-fired combined-cycle generation by 2035 and an additional 1,200 MWs by 2040;

•adding 3,200 MWs of renewable generation by 2030, which includes the solar generation projects discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report, and an additional 1,500 MWs by 2035;

•adding 1,000 MWs of battery storage by 2030, which includes the Big Hollow Battery Energy Storage Project discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report, and an additional 800 MWs by 2042;

•adding 1,500 MWs of nuclear generation by 2040;

•retiring all of Ameren Missouri’s coal-fired energy centers by 2042;

•retiring 1,800 MWs of Ameren Missouri’s natural gas-fired energy centers by 2040 to comply with Illinois law;

•the continued implementation of customer energy-efficiency and demand response programs; and

•the expectation that Ameren Missouri will seek and receive NRC approval for an extension of the operating license for the Callaway Energy Center beyond its current 2044 expiration date.

The addition of renewable, natural gas-fired, or nuclear generation facilities is subject to obtaining necessary project approvals, including FERC approval and the issuance of a CCN by the MoPSC, as applicable. Additionally, in February 2026, Ameren Missouri executed electric service agreements with large load customers under the large load customer rate plan, representing 2.2 gigawatts of demand. See Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report for more information on the large load customer rate plan. Ameren Missouri expects to file its next preferred resource plan in September 2026.

The PPRA became effective in August 2025. The law made modifications to integrated resource planning, which requires Missouri electric utilities to file plans for meeting their customers' long-term energy needs. By August 2027, the MoPSC will publish a schedule for Missouri electric utilities to file integrated resource plans every four years. The MoPSC will be required to issue an order on the plans and shall determine whether the electric utility has submitted sufficient documentation and selected preferred resource plans representing a reasonable and prudent means of serving the utility's load obligations at just and reasonable rates. In making this determination, the MoPSC shall consider whether the plans appropriately balance specific factors described in the law. If the MoPSC approves the plans, requests for CCNs for new generation facilities to be constructed or acquired as a part of the approved plans shall be deemed necessary and convenient and the scope of the CCN proceedings to review projects will be limited. The approved generation facilities will also be eligible to include construction work in progress in rate base, subject to MoPSC approval, which would improve the timeliness of cash recovery. Utilities are not allowed to capitalize allowance for funds used during construction on amounts included in rate base under this provision. The amount of construction work in progress to be included in rate base is limited to prudently incurred expenditures made within the construction period for the facility.

Ameren Missouri continues to evaluate its longer-term needs for new generating capacity. The need for investment in new sources of energy is dependent on several key factors, including continuation of and customer participation in energy-efficiency programs, the amount of distributed generation from customers, load growth, including demand from data centers, technological advancements, costs of generation alternatives, environmental regulation of coal-fired and natural gas-fired power plants, changes in United States energy policy and priorities under the presidential administration, and state renewable energy requirements, which could lead to the retirement of current baseload assets before the end of their current useful lives or alterations in the way those assets operate, which could result in increased capital expenditures and/or increased operations and maintenance expenses. Because of the significant time required to plan, acquire permits for, and build a baseload energy center, Ameren Missouri continues to study alternatives and to take steps to preserve options to meet future demand. Steps include evaluating the potential for further diversification of Ameren Missouri’s generation portfolio through renewable energy generation, including wind and solar generation, natural gas-fired generation, including the potential to blend hydrogen fuel with natural gas and install carbon capture technology, extending the operating license for the Callaway Energy Center, adding new nuclear generation, additional customer energy-efficiency and demand response programs, distributed energy resources, and energy storage.

Missouri law requires that Ameren Missouri offers net metering to certain customers that install renewable generation at their premises. Customers that elect to enroll in net metering are allowed to net their generation against their distribution usage within each billing month.

Ameren Illinois

In Illinois, while electric transmission and distribution service rates are regulated, power supply prices are not. Although electric customers are allowed to purchase power from an alternative retail electric supplier, Ameren Illinois is required to be the provider of last resort for its electric distribution customers. In 2025, 2024, and 2023, Ameren Illinois procured power on behalf of its customers for 28%, 25%, and 28%, respectively, of its total kilowatthour sales. Power purchased by Ameren Illinois for its electric distribution customers who do not elect to purchase their power from an alternative retail electric supplier comes either through procurement processes conducted by the IPA or through markets operated by the MISO. The IPA administers an RFP process through which Ameren Illinois procures its expected

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supply. The purchased power and related procurement costs incurred by Ameren Illinois are passed directly to its electric distribution customers through a cost recovery mechanism. Transmission costs are charged to customers who purchase electricity from Ameren Illinois through a cost recovery mechanism. The purchased power, power procurement, and transmission costs are reflected in Ameren Illinois Electric Distribution’s results of operations, but do not affect Ameren Illinois Electric Distribution’s earnings because these costs are offset by corresponding revenues. Ameren Illinois charges distribution service rates to electric distribution customers who purchase electricity, regardless of supplier, which does affect Ameren Illinois Electric Distribution’s earnings.

Pursuant to Illinois law, Ameren Illinois is required to file a Grid Plan with the ICC every four years. In December 2024, the ICC issued an order approving Ameren Illinois’ revised Grid Plan under its MYRP proceeding for electric distribution service for 2024 through 2027. For additional information regarding Ameren Illinois’ MYRP proceeding, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report. The Grid Plan outlines how Ameren Illinois expects to invest in electric distribution infrastructure in order to support grid modernization, clean energy, energy efficiency, and the state of Illinois’ renewable energy, equity, climate, electrification, and environmental goals. In January 2026, Ameren Illinois filed its Grid Plan for the years 2028 through 2031. The Grid Plan will be used to align capital expenditures to operational needs and will impact rate base for future rate reviews under an MYRP or traditional rate review. An order from the ICC is expected in December 2026.

In addition, pursuant to the CRGA, Ameren Illinois will participate in an integrated resource planning process, which is designed to align statewide electric supply and demand and establish a plan for electricity resources to reliably, affordably, and efficiently serve Illinois customers while meeting clean energy targets at the lowest cost over time. The ICC staff, the IPA, the Illinois Finance Authority, and the Illinois Environmental Protection Agency must submit the initial integrated resource plan to the ICC no later than November 15, 2026, the second integrated resource plan to the ICC no later than September 30, 2029, and each subsequent plan to the ICC every four years thereafter no later than September 30 of the applicable year.

Illinois law currently requires Ameren Illinois to offer rebates and net metering to certain customers who install renewable generation. The cost of the customer generation rebate program is deferred as a regulatory asset, which earns a return at the applicable WACC, with the ROE based on the annual average of the monthly average yields of the 30-year United States Treasury bonds plus 580 basis points through 2026. Pursuant to the CRGA, standalone energy storage systems will also be eligible for rebates, and the return on the deferred regulatory asset will be equal to the most recently approved ROE for Ameren Illinois electric distribution, beginning in January 2027. The eligibility of standalone energy storage systems for rebates is subject to ICC approval, with the tariff filing due in the second half of 2026. Ameren Illinois expects a decision on the tariff filing by the end of 2026. By law, Ameren Illinois’ electric distribution revenues are decoupled from sales volumes, which ensures that the electric distribution revenues authorized in a regulatory rate review are not affected by changes in sales volumes.

POWER GENERATION

Ameren Missouri owns energy centers that rely on a diverse fuel portfolio, including coal, nuclear, and natural gas, as well as renewable sources of generation. Both of Ameren Missouri’s coal-fired energy centers were constructed prior to 1978. As of December 31, 2025, Ameren Missouri’s coal-fired energy centers represented 5% and 11% of Ameren’s and Ameren Missouri’s rate base, respectively. The Callaway Energy Center began operation in 1984 and is currently licensed to operate until 2044. Ameren Illinois operates two solar generation facilities, which are two of three pilot solar projects Ameren Illinois is allowed to invest in under the CEJA. The third solar generation facility is planned to be placed in service before the end of 2026. See Item 2 – Properties under Part I of this report for information regarding our energy centers.

Coal

Ameren Missouri has an ongoing need for coal as fuel for generation, and pursues a price-hedging strategy consistent with this requirement. Ameren Missouri has agreements in place to purchase and transport coal to its energy centers. While Ameren Missouri has minimum purchase obligations associated with these agreements, the majority of these agreements are not associated with any specific coal-fired energy center. Ameren Missouri burned approximately 12.0 million tons of coal in 2025. For information regarding the percentages of Ameren Missouri’s projected required supply of coal and coal transportation that are price-hedged through 2030, see Commodity Price Risk under Part II, Item 7A, of this report.

Approximately 96% of Ameren Missouri’s coal is purchased from the Powder River Basin in Wyoming, which has a limited number of suppliers. The remaining coal is typically purchased from the Illinois Basin. Targeted coal inventory levels may be adjusted because of generation levels or uncertainties of supply due to delays in coal deliveries, equipment breakdowns, and other factors. Deliveries from the Powder River Basin have occasionally been restricted because of rail congestion, staffing and equipment issues, infrastructure maintenance, derailments, weather, and supplier financial hardship. Delays and disruptions in coal deliveries could cause Ameren Missouri to pursue a strategy that could include reducing off-system sales of power during low-earning periods, buying higher-cost fuels to generate required electricity, and purchasing power from other sources.

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Nuclear

The production of nuclear fuel involves the mining and milling of uranium ore to produce uranium concentrates, the conversion of uranium concentrates to uranium hexafluoride gas, the enrichment of that gas, the conversion of the enriched uranium hexafluoride gas into uranium dioxide fuel pellets, and the fabrication into fuel assemblies. Ameren Missouri has entered into uranium, uranium conversion, uranium enrichment, and fabrication contracts to procure the fuel supply for its Callaway Energy Center.

The Callaway Energy Center requires refueling at 18-month intervals. The last refueling was completed in July 2025. The next refueling is scheduled for the fall of 2026. Ameren Missouri has inventories and supply contracts sufficient to meet all of its uranium (concentrate and hexafluoride), conversion, enrichment, and fabrication requirements at least through the fall 2029 refueling.

Renewable

Ameren Missouri operates several renewable energy centers, which includes hydroelectric, wind, methane gas, and solar energy centers. The High Prairie and Atchison energy centers are wind generation facilities. The Huck Finn, Boomtown, Cass County, and Vandalia energy centers are solar generation facilities. In February 2026, Ameren Missouri acquired the Split Rail Solar Project, which is expected to be placed in service in the second quarter of 2026. The Osage and Keokuk energy centers generate electricity using hydroelectric dams located on the Lake of the Ozarks and the Mississippi River, respectively. The Taum Sauk Energy Center is a pumped-storage hydroelectric facility that generates electricity by releasing water from an upper reservoir through turbines into a lower reservoir during periods of high demand, then pumping the water back up during off-peak hours for reuse. The Maryland Heights Energy Center generates electricity by burning methane gas collected from a landfill. For additional information regarding newly constructed or acquired energy centers, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

RENEWABLE ENERGY AND ZERO EMISSION STANDARDS

Missouri and Illinois laws require electric utilities to include renewable energy resources in their portfolios. Ameren Missouri and Ameren Illinois satisfied their renewable energy resource requirements in 2025, pending regulatory review by the MoPSC for Ameren Missouri.

Ameren Missouri

In Missouri, utilities are required to purchase or generate electricity equal to at least 15% of native load sales from renewable energy sources, with at least 2% of the requirement derived from solar energy. The requirement is subject to an average 1% annual limit on increases to customer rates over any 10-year period. For renewable generation facilities located in Missouri, 125% of the electricity generated counts towards meeting the requirement. Ameren Missouri expects to satisfy the requirement in 2026 with its High Prairie, Atchison, Huck Finn, Keokuk, Maryland Heights, and other solar energy centers, along with other renewable energy credits purchased by Ameren Missouri, including solar-generated renewable energy credits purchased from customer-installed systems.

Ameren Illinois

In accordance with Illinois law, Ameren Illinois is required to collect funds from all electric distribution customers to fund IPA procurement events for renewable energy credits. The amount set by law and required to be collected from customers by Ameren Illinois is currently $4.58 per MWh. Beginning June 2026, the CRGA will increase the amount of customer collections by adding an annual inflation adjustment to the $4.58 per MWh charge. The IPA establishes its long-term renewable resources procurement plans in a filing made every two years. In February 2026, the ICC approved the IPA’s latest long-term renewable resources procurement plan, which established the 2026 and 2027 renewable energy credit procurement targets. Based on IPA procurement events that align with the IPA’s plan, Ameren Illinois has contractual commitments to purchase approximately 3.1 million wind renewable energy credits per year and approximately 4.1 million solar renewable energy credits per year. Ameren Illinois has also entered into contracts, ending in 2032, to purchase approximately 0.6 million wind renewable energy credits per year. Pursuant to the CEJA, if funds collected from customers are not used to procure renewable energy credits, they would be refunded to customers pursuant to an annual reconciliation proceeding. The first two reconciliations, covering June 2017 through May 2018 and June 2018 through May 2019, were approved by the ICC in January 2025 and May 2025, respectively, and did not result in refunds to customers. Based on amounts collected from customers and obligations under the program, the June 2019 through May 2020 reconciliation period is not expected to result in refunds to customers, pending review by the ICC.

The CRGA establishes an energy storage credit program, under which the IPA must hold statewide procurements for energy storage credits. The program requires Illinois utilities to enter into 20-year contracts to procure energy storage credits, with delivery of the credits beginning no later than 2030. Ameren Illinois anticipates utilizing cost recovery mechanisms to allow Ameren Illinois to collect from, or refund to, customers differences between actual costs incurred from the purchase of the credits and the amounts collected from customers. For additional information regarding the CRGA, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.

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Illinois law also required Ameren Illinois to enter into contracts to purchase zero emission credits in an amount equal to approximately 16% of the actual amount of electricity delivered to retail customers during calendar year 2014, pursuant to Illinois’ zero emission standard. As a result of a 2018 IPA procurement event, which was approved by the ICC, Ameren Illinois entered into agreements to acquire zero emission credits through May 2027. Annual zero emission credit commitment amounts will be published by the IPA each May prior to the start of the subsequent planning year. Both renewable energy credits and zero emission credits have cost recovery mechanisms, which allow Ameren Illinois to collect from, or refund to, customers differences between actual costs incurred from the purchase of the credits and the amounts collected from customers.

CUSTOMER ENERGY-EFFICIENCY PROGRAMS

Ameren Missouri and Ameren Illinois have implemented energy-efficiency programs to educate their customers and to help them become more efficient energy consumers. These programs provide incentives to customers for installing newer, more efficient technology, and for using energy in a more conservation-minded manner. As a component of the energy-efficiency programs, Ameren Missouri and Ameren Illinois have invested in electric smart meters to provide customers more visibility to their energy consumption and facilitate more efficient use of energy. As of December 31, 2025, Ameren Missouri and Ameren Illinois have completed the transition to smart meters, which have been installed for nearly all electric and natural gas customers.

Ameren Missouri

In Missouri, the Missouri Energy Efficiency Investment Act established a rider that, among other things, allows electric utilities to recover costs with respect to MoPSC-approved customer energy-efficiency programs. The law requires the MoPSC to ensure that a utility’s financial incentives are aligned to help customers use energy more efficiently, to provide timely cost recovery, and to provide earnings opportunities associated with cost-effective energy-efficiency and demand response programs. Missouri does not have a law mandating energy-efficiency or demand response programs.

In 2024, the MoPSC issued an order approving a nonunanimous stipulation and agreement for Ameren Missouri’s MEEIA 2025 plan, which includes a portfolio of customer energy-efficiency and demand response programs, along with the continued use of the MEEIA rider. Ameren Missouri intends to invest $51 million in 2026 and $22 million in 2027 for customer energy-efficiency and demand response programs. In addition, the order approved an immaterial amount of performance incentives applicable to each plan year to earn revenues by achieving certain spending and demand response goals.

The MEEIA rider allows Ameren Missouri to collect from customers its actual program costs, lost electric revenues, and any performance incentive, without a traditional regulatory rate review, subject to MoPSC prudence reviews, until lower volumes resulting from the MEEIA programs are reflected in base rates. Customer rates, based upon both forecasted program costs and lost electric revenues and collected via the MEEIA rider, are reconciled annually to actual results.

Ameren Illinois

Pursuant to Illinois law, Ameren Illinois offers customer energy-efficiency programs and is subject to electric energy-efficiency savings goals and a maximum annual amount of investment in electric energy-efficiency programs. Every four years, Ameren Illinois is required to file a four-year electric energy-efficiency plan with the ICC. In August 2025, the ICC issued an order approving Ameren Illinois’ energy-efficiency plan that includes annual investments in electric energy-efficiency programs of approximately $126 million per year from 2026 through 2029. Pursuant to the CRGA, Ameren Illinois is required to file an updated electric energy-efficiency plan for 2027 through 2029 by June 1, 2026 to reflect a higher annual cap on spending. Ameren Illinois’ planned investments in electric energy-efficiency programs under the revised annual cap is approximately $126 million in 2026, $178 million in 2027, $222 million in 2028, and $256 million in 2029.

Illinois law allows Ameren Illinois to earn a return on its electric energy-efficiency program investments. Ameren Illinois’ electric energy-efficiency investments are deferred as a regulatory asset and earn a return at the applicable WACC, with the ROE currently based on the annual average of the monthly yields of the 30-year United States Treasury bonds plus 580 basis points. Pursuant to the CRGA, beginning in 2027, the ROE for electric energy-efficiency investments will be based on the most recently approved Ameren Illinois electric distribution ROE. The allowed ROE on electric energy-efficiency investments can be increased or decreased by up to 200 basis points, depending on the achievement of annual energy savings and demand goals. While the ICC approves Ameren Illinois’ four-year electric energy-efficiency plans, the ICC has the ability to reduce the amount of approved electric energy-efficiency savings goals in future plan program years if there are insufficient cost-effective programs available, which could reduce the investments in electric energy-efficiency programs. The electric energy-efficiency program investments and the return on those investments are collected from customers through a rider and are not included in the electric distribution service MYRP or traditional regulatory rate review frameworks. Ameren Illinois’ natural gas energy-efficiency program costs are recovered through a separate gas rider.

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NATURAL GAS SUPPLY FOR DISTRIBUTION

Ameren Missouri and Ameren Illinois are responsible for the purchase and delivery of natural gas to their customers. Ameren Missouri and Ameren Illinois each develop and manage a portfolio of natural gas supply resources. These resources include firm natural gas supply agreements, firm interstate and intrastate transportation capacity, firm no-notice storage capacity leased from interstate pipelines, and on-system storage facilities to maintain natural gas deliveries to customers throughout the year and especially during peak demand periods. Ameren Missouri and Ameren Illinois primarily use Panhandle Eastern Pipe Line Company, Trunkline Gas Company, Natural Gas Pipeline Company of America, Mississippi River Transmission Corporation, Northern Border Pipeline Company, Spire MoGas Pipeline, and Texas Eastern Transmission Corporation interstate pipeline systems to transport natural gas to their systems. In addition to transactions requiring physical delivery, certain financial instruments, including those entered into in the over-the-counter financial markets, are used to hedge the price paid for natural gas. Natural gas supply costs are passed on to customers of Ameren Missouri and Ameren Illinois under PGA clauses, subject to prudence reviews by the MoPSC and the ICC. For information regarding the percentage of Ameren Missouri’s and Ameren Illinois’ projected remaining natural gas supply requirements that are price-hedged through 2031, see Commodity Price Risk under Part II, Item 7A, of this report.

For additional information on our fuel, purchased power, and natural gas for distribution supply, see Results of Operations and Liquidity and Capital Resources in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, and Commodity Price Risk under Part II, Item 7A, of this report. Also see Note 1 – Summary of Significant Accounting Policies, Note 7 – Derivative Financial Instruments, Note 13 – Related-party Transactions, Note 14 – Commitments and Contingencies, and Note 15 – Supplemental Information under Part II, Item 8, of this report.

HUMAN CAPITAL MANAGEMENT

The execution of Ameren’s core strategy to invest in rate-regulated energy infrastructure, enhance regulatory frameworks and advocate for responsible policies, and optimize operating performance is driven by the capabilities and engagement of our workforce. Ameren’s workforce strategy is designed to promote a skilled workforce that is well-prepared to deliver on Ameren’s mission (To Power the Quality of Life) and vision (Leading the Way to a Sustainable Energy Future), both today and in the future. Our workforce strategy is anchored in four key pillars: Culture; Leadership Development; Organizational Alignment and Work Optimization; and Talent Attraction, Development and Rewards, which are discussed further below.

We are committed to workforce practices that adhere to laws and regulations regarding non-discrimination. We make employment decisions based on merit, without regard to any characteristic protected by law, and reinforce this commitment through robust risk management practices, ongoing legal monitoring, mandatory non-discrimination training, and employee feedback mechanisms.

Strong governance further supports these efforts. Ameren’s Chief Executive Officer and our Chief Human Resources Officer, with the support of other leaders of the Ameren Companies, are responsible for developing and executing our workforce strategy. In addition to reviewing and determining the Ameren Companies’ compensation practices and policies for the Chief Executive Officer and other executive officers, the Human Resources Committee of Ameren’s board of directors is responsible for oversight of Ameren’s human capital management practices and policies. The Human Resources Committee and Ameren’s board of directors are updated regularly on culture, organizational structure, leadership development, and legal and compliance matters.

Culture

We design our human capital management practices and policies to instill and reinforce our core values (Safety, Accountability, Integrity, Respect, and Stewardship) and organization competencies (Be Strategic, Continuously Improve, Deliver Results, Engage Respectfully, Foster Collaboration, and Think Customer). In doing so, we strive to align our employees to our mission and vision, improve safety, continuously improve operating performance, attract and retain top talent, and recognize employee contributions, among other things. We seek employee feedback through confidential surveys and other channels, using insights to enhance the employee experience and take actions aimed at increasing employee engagement. We have enhanced our facilities and workforce policies and practices to increase collaboration and productivity.

As a part of our culture, every employee is expected to challenge any unsafe act, complete each workday safely, and provide feedback on safety and security matters. In addition to comprehensive safety and security standards, and mandatory health, safety, and security training programs for applicable employees, we promote programs designed to encourage employees to provide feedback on practices or actions that could harm employees, customers, or the Ameren Companies, including perceived issues related to safety, security (both physical and cyber), ethics and compliance violations, or policy concerns.

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Leadership Development

Ameren’s leaders play a critical role in setting and executing Ameren’s strategic initiatives, modeling our values and culture, and engaging and enabling the workforce. As such, we seek to develop a strong leadership team with a variety of experiences and perspectives. Management engages in an extensive succession planning process annually, which includes the involvement of Ameren’s board of directors. We develop our leaders both individually, through job rotations, coaching, work experiences, and leadership development programs, and as a team. Throughout the year, we offer a variety of forums intended to connect our leaders to our mission, vision, values, strategy, and culture, and to build leadership skills and capabilities.

Organizational Alignment and Work Optimization

We regularly evaluate our organizational structure and make adjustments and expand roles to facilitate execution of our strategy and organizational efficiency. We take proactive and intentional actions to ensure that structure is aligned with our highest priorities, processes are streamlined, technology is leveraged to drive efficiency and productivity, and roles are structured to facilitate communication, ownership and accountability.

Talent Attraction, Development, and Rewards

We engage in a variety of internal and external workforce development initiatives to ensure we have a strong pipeline of talent with the skills needed to execute our strategic priorities. We invest in our people to build or enhance technical, leadership, and professional skills and we facilitate mentoring relationships across the organization. As our business needs change, we remain focused on ensuring that our workforce has the tools and skills necessary to deliver on our strategic initiatives.

Our talent management initiatives include a wide range of recruiting partnerships and programs, designed to engage a variety of career seekers. We have established programs to recruit early and mid-career talent to further enhance our workforce pipelines. These programs include skilled craft education and training for individuals interested in skilled craft roles, an intern/co-op program that serves as a pipeline for STEM-related careers, a program for individuals transitioning from military service, and an early career rotation program.

Complementing these efforts, our rewards program delivers a competitive and financially sustainable total rewards package that reinforces strong performance and supports engagement. We recognize that the rewards package required to attract and retain talent over the long term is about more than pay and benefits; it is about the total employee experience and support of their overall well-being. In addition to base salary, medical benefits, and retirement benefits, including defined benefit pension plans covering substantially all employees and a 401(k) plan for eligible employees, our total rewards package includes short-term incentives and long-term stock-based compensation for certain employees. Further, we offer our employees various programs that encourage overall well-being, including wellness and employee assistance programs. We regularly evaluate our offerings to ensure they provide meaningful value to employees while maintaining fiscal responsibility – enabling Ameren to attract, retain, and motivate top talent to achieve our strategic objectives.

Workforce

The majority of our workforce is comprised of skilled-craft and STEM-related professional and technical employees. Our workforce has been stable, with a total attrition rate of 6% in 2025. The majority of employee attrition is a result of employee retirements, generally allowing for thoughtful workforce and succession planning in advance of these planned transitions. The following table presents our employee count and their average tenure as of December 31, 2025, and the attrition rate in 2025:

The following table presents Ameren’s employees by generation as of December 31, 2025:

Collective bargaining units at Ameren’s subsidiaries consist of the International Brotherhood of Electrical Workers, the International Union of Operating Engineers, the Laborer’s International Union of North America, the United Association of Plumbers and Pipefitters, and

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the United Government Security Officers of America. As of December 31, 2025, these labor unions collectively represented 46%, 58%, 54%, and 10% of the employees at Ameren, Ameren Missouri, Ameren Illinois, and Ameren Services, respectively. The Ameren Companies expect continued constructive relationships with their respective labor unions. The Ameren Missouri collective bargaining unit contracts expire in 2026 and 2028, and cover 96% and 4% of represented employees, respectively. The Ameren Illinois collective bargaining unit contracts expire in 2027 and 2029, and cover 8% and 92% of represented employees, respectively. Ameren Missouri and Ameren Illinois expect to renew these contracts prior to their expiration, however there can be no guarantee that such renewals will be secured on favorable terms.

INDUSTRY ISSUES

We are facing issues common to the electric and natural gas utility industry, as well as new and emergent issues impacting the industry as a whole. These issues include:

•the potential for changes in laws, regulations, enforcement efforts, and policies at the federal, state, and international levels, including but not limited to environmental laws and the presidential administration’s change in federal domestic energy policy to support investments in fossil fuel infrastructure and the effect it may have on the ability to construct and/or acquire renewable energy generation facilities and battery storage;

•corporate tax law changes, including the OBBBA and the IRA, as well as additional interpretations, regulations, amendments, or technical corrections that affect the amount and timing of income tax payments or the transferability of production and investment tax credits, reduce or limit the ability to claim certain deductions and use carryforward tax benefits and/or credits, or result in rate base reductions;

•maintaining affordability of electric and natural gas utility services for customers, including the demand for access to renewable energy generation, at rates acceptable to customers;

•political, regulatory, and customer resistance to higher rates;

•cybersecurity risks, cyber attacks, including ransomware and other ransom-based attacks and those attacks arising from or generated by generative or agentic artificial intelligence, hacking, social engineering, and other forms of malicious cybersecurity and/or privacy events, which could result in the loss of operational control of energy centers and electric and natural gas transmission and distribution systems and/or the theft or inappropriate release of certain types of information, including sensitive customer, employee, financial, and operating system information;

•acts of sabotage, which in recent years have increased in frequency and severity within the utility industry, terrorism, and other intentionally disruptive acts;

•the impacts from new data centers expected to be constructed over the next several years, including increased competition among utilities, independent power producers and non-traditional market entrants, providing generation and resource adequacy to support the projected load growth, managing the impact on customer rates, and the possibility that future demand from data centers may not be realized at the current projected pace;

•pressure and uncertainty on customer growth and sales volumes in light of increased competition in the industry and economic conditions;

•the impact and effectiveness of vegetation management programs;

•the potential for reliability issues due to inadequate resources resulting from the retirement of fossil-fuel-fired generation facilities as they are replaced with renewable energy generation sources, increasing load growth, and market inefficiencies related to prices for purchased power, capacity, and ancillary services, and other factors;

•the need to place new transmission and generation facilities in service, which is dependent upon timely regulatory approvals and the availability of necessary labor and materials, among other things, to maintain grid reliability;

•the ability to recover and earn a fair return on investments due to changes in the allowed ROE, including ROE incentive adders on FERC-regulated electric transmission assets;

•the influence of macroeconomic factors on yields of United States Treasury securities and on the allowed ROE provided by regulators;

•regulatory lag;

•the availability of fuel, materials and supplies, and equipment, and the potential disruptions in supply chains and inflationary pressures or tariffs on the prices and availability of commodities, labor, services, materials and supplies, and impacts associated with extended recovery periods from customers;

•the availability of a skilled work force, including transferring the specialized knowledge of those who are nearing retirement to employees succeeding them;

•the modernization of the electric grid to accommodate a two-way flow of electricity and increased capacity for distributed generation interconnection;

•net metering rules and other changes in existing regulatory frameworks and recovery mechanisms to address the allocation of costs to customers who own generation resources that enable them both to sell power to us and to purchase power from us through the use of our transmission and distribution assets;

•legislation or programs to encourage or mandate energy efficiency, energy conservation, and renewable sources of power, and the lack of consensus as to how those programs should be paid for;

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•higher levels of infrastructure and technology investments and adjustments to customer rates associated with the refund of excess deferred income taxes that have resulted in, and are expected to continue to result in, negative or decreased free cash flow, which is defined as cash flows from operating activities less cash flows from investing activities and dividends paid;

•public concerns about the siting of new facilities, and challenges that members of the public can assert against applications for governmental permits and other approvals required to site and build new facilities that can result in significant cost increases, delays and denial of the permits and approvals by the regulators;

•public concerns about the potential environmental impacts from the combustion of fossil fuels;

•pressure from public interest groups regarding limiting the use of natural gas, as well as proposed restrictions on the use of natural gas by state and local authorities;

•certain investors’ concerns about investing in, as well as certain insurers’ concerns about providing coverage to, utility companies that have coal-fired generation assets;

•scrutiny by investors and other stakeholders of industry practices;

•public concerns about nuclear energy and the disposal of nuclear waste;

•industry challenges resulting from alleged or actual legal, regulatory, or compliance failures, including in connection with lobbying and political activities or liabilities arising out of wildfires or other catastrophic events; and

•effects of mergers, acquisitions, and divestitures within the utility industry.

We are monitoring all these issues. Except as otherwise noted in this report, we are unable to predict what impact, if any, these issues will have on our results of operations, financial position, or liquidity. For additional information, see Risk Factors under Part I, Item 1A, Outlook in Management’s Discussion and Analysis of Financial Condition and Results of Operations under Part II, Item 7, and Note 2 – Rate and Regulatory Matters, Note 9 – Callaway Energy Center, and Note 14 – Commitments and Contingencies under Part II, Item 8, of this report.

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OPERATING STATISTICS

The following tables present key electric and natural gas operating statistics for Ameren for the past three years:

(a)Sales for which power was supplied by Ameren Illinois as well as alternative retail electric suppliers. In 2025, 2024, and 2023, Ameren Illinois procured power on behalf of its customers for 28%, 25%, and 28%, respectively, of its total kilowatthour sales.

(b)Includes $160 million, $119 million, and $113 million in 2025, 2024, and 2023, respectively, of electric operating revenues from transmission services provided to Ameren Illinois Electric Distribution.

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(a)    Ameren Missouri fuel costs exclude $(96) million, $34 million, and $72 million in 2025, 2024, and 2023, respectively, for changes in FAC recoveries.

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AVAILABLE INFORMATION

The Ameren Companies make available free of charge through Ameren’s website (www.amereninvestors.com) their annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K, and any amendments to those reports filed with or furnished to the SEC pursuant to Sections 13(a) or 15(d) of the Exchange Act as soon as reasonably possible after such reports are electronically filed with, or furnished to, the SEC. These documents are also available through the SEC’s website (www.sec.gov). Ameren’s website is a channel of distribution for material information about the Ameren Companies. Financial and other material information is routinely posted to, and accessible at, Ameren’s website.

The Ameren Companies also make available free of charge through Ameren’s website the charters of Ameren’s board of directors’ Audit and Risk Committee, Cybersecurity and Digital Technology Committee, Finance Committee, Human Resources Committee, Nominating and Corporate Governance Committee, and Nuclear, Operations and Environmental Sustainability Committee; the corporate governance guidelines; a policy regarding communications to the board of directors; a policy and procedures document with respect to related-person transactions; a code of ethics applicable to all directors, officers and employees; a supplemental code of ethics for principal executive and senior financial officers; and a director nomination policy that applies to the Ameren Companies. In addition, we provide information regarding our sustainability initiatives through our website, including our annual sustainability and impact report and a sustainability investor presentation. The information or other documents on Ameren’s website, or any other website referenced in this report, is not incorporated by reference into this report.