What changed in this filing

/stocks — the workspaceLOADING

Item 1. Business

2026-02-18 compared with 2025-02-18 · 143 added, 115 removed, 355 unchanged (42% of the section changed)

22 unchanged sentences

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

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

(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

21 unchanged sentences

Electric service (b)

MoPSC June 2023 July 2023 (c) (c) (c) 50%

Natural gas delivery service MoPSC December 2021 February 2022 (d) (d) $0.3 2%

MoPSC April 2025 June 2025 (c) (c) (c) 52%

Natural gas delivery service MoPSC July 2025 September 2025 (c) (c) (c) 2%

Ameren Illinois

Electric distribution delivery service (e)

ICC December 2024 (e) 8.72% 50.00% (e) 27%

Electric distribution delivery service (d)

ICC December 2024 (d) 8.72% 50.00% (d) 26%

Electric energy-efficiency investments (e)

ICC November 2025 January 2026 10.65% 50.00% $0.5 1%

Natural gas delivery service (f)

ICC November 2023 November 2023 9.44% 50.00% $2.8 12%

ICC November 2025 December 2025 9.60% 50.00% $3.2 11%

Electric transmission service (g)

6 unchanged sentences

(d) This rate order did not specify an ROE or a capital structure.

(e) In December 2024, the ICC issued an order in Ameren Illinois’ MYRP proceeding.

The order 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.

Rate changes consistent with the December 2024 order became effective in late December 2024.

Under an MYRP, Ameren Illinois will reconcile 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.

(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.

9 unchanged sentences

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 for the purpose of implementing and enforcing reliability standards approved by the FERC.

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 work to safeguard the reliability of the bulk power systems throughout North America.

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.

2 unchanged sentences

Operation of Ameren Missouri’s Callaway Energy Center is subject to regulation by the NRC.

The license for the Callaway Energy Center expires in 2044.

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.

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.

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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.

These environmental statutes and regulations are comprehensive and include the storage, handling, and disposal of waste materials and hazardous substances, emergency planning and response requirements, limitations and standards applicable to discharges from our facilities into the air or water that are enforced through permitting requirements, and natural resource protection laws, including those related to endangered species.

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.

Recent and potential new executive orders issued by the current federal administration as well as local and state land use requirements can also impact our planning activities.

For discussion of environmental matters, including NO x and SO 2 emission reduction requirements, regulation of CO 2 emissions, wastewater discharge standards, remediation efforts, and CCR management regulations, and a discussion of litigation against Ameren Missouri with respect to NSR, the Clean Air Act, and Missouri law in connection with projects at Ameren Missouri’s Rush Island Energy Center, see Note 14 – Commitments and Contingencies under Part II, Item 8, of this report.

Executive orders issued by the presidential administration as well as local and state land use requirements can also impact our planning activities.

Ameren owns an integrated transmission system that is composed of the transmission assets of Ameren Missouri, Ameren Illinois, and ATXI.

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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

Ameren Missouri sells 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 capacity from the MISO and through bilateral contracts resulting from IPA procurement events.

In 2022, the FERC issued an order approving changes to the annual MISO capacity auction.

Historically, the auctions were designed to cover annual peak demand plus a target reserve margin.

Beginning with the April 2023 auction for the June 2023 to May 2024 planning year, auctions include four seasonal load forecasts and available capacity levels and are designed to cover each season’s peak demand plus a target reserve margin.

The seasonal auction structure was established to help to address variability in resources as the MISO begins to rely more heavily on renewable generation.

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

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Ameren Missouri files a long-term nonbinding preferred resource plan with the MoPSC every three years.

The most recent preferred resource plan was filed in September 2023.

Ameren Missouri expects to file a notice of change in its 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 is expected to include, among other things, the following:

• adding 1,600 MWs of natural gas-fired simple-cycle generation by 2030, which includes the 800-MW Castle Bluff Natural Gas Project discussed in Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report, and an additional 1,200 MWs by 2043;

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:

• 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 900 MWs of 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 and an additional 800 MWs by 2042;

• 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;

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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.

Ameren Missouri would be adversely affected if the MoPSC does not allow recovery of the remaining investment and decommissioning costs associated with the retirement of an energy center, as well as the ability to earn a return on that remaining investment and those decommissioning costs.

The next preferred resource plan is required to be filed by October 2026.

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 current federal 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.

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 switch to hydrogen fuel and/or blend hydrogen fuel with natural gas and install carbon capture technology, extending the operating license for the Callaway Energy Center, additional customer energy-efficiency and demand response programs, distributed energy resources, and energy storage.

Missouri law required Ameren Missouri to offer solar rebates through December 2023 and currently requires Ameren Missouri to offer net metering to certain customers that install renewable generation at their premises.

The difference between the cost of the solar rebates and the amount set in base rates was deferred as a regulatory asset or liability under the RESRAM, and earns carrying costs at short-term interest rates.

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.

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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 supply.

The IPA administers an RFP process through which Ameren Illinois procures its expected

The purchased power and related procurement costs incurred by Ameren Illinois are passed directly to its electric distribution customers through a cost recovery mechanism.

2 unchanged sentences

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 the CEJA, Ameren Illinois is required to file a Grid Plan with the ICC every four years.

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

Ameren Illinois’ next Grid Plan is required to be filed by mid-January 2026.

Illinois law requires Ameren Illinois to offer rebates and net metering to certain customers who install renewable generation or paired energy storage systems at their premises.

The cost of the customer generation rebate program is deferred as a regulatory asset, which earns a return at the applicable WACC.

Customers that elect to receive a generation rebate and are enrolled in net metering are allowed to net their power supply service charges, but not their distribution service charges.

Customers that elect to receive energy storage rebates and have not received generation rebates are allowed to net their power supply and distribution service charges.

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.

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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 licensed to operate until 2044.

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.

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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.

About 97% of Ameren Missouri’s coal is purchased from the Powder River Basin in Wyoming, which has a limited number of suppliers.

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.

5 unchanged sentences

The Callaway Energy Center requires refueling at 18-month intervals.

The last refueling was completed in November 2023.

The next refueling is scheduled for the spring of 2025.

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 spring 2028 refueling.

The last refueling was completed in July 2025.

The next refueling is scheduled for the fall of 2026.

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, and Cass County energy centers are solar 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 portfolio requirements in 2024, pending regulatory review by the MoPSC for Ameren Missouri.

Ameren Missouri and Ameren Illinois satisfied their renewable energy resource requirements in 2025, pending regulatory review by the MoPSC for Ameren Missouri.

Ameren Missouri

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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 capped at $4.58 per MWh.

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.

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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 of which was approved by the ICC in January 2025, which was the June 2017 through May 2018 reconciliation period, and did not result in refunds to customers.

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.

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.

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Missouri does not have a law mandating energy-efficiency or demand response programs.

In November 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 annually in 2025 and 2026 and $22 million in 2027 for customer energy-efficiency and demand response programs.

In addition, the order approved performance incentives applicable to each plan year to earn revenues by achieving certain spending and demand response goals.

If 100% of the goals are achieved in 2025, 2026, and 2027, Ameren Missouri would earn performance incentive revenues of $5 million, $5 million, and $2 million, respectively.

Through 2024, Ameren Missouri has invested approximately $415 million in MEEIA 2019 customer energy-efficiency and demand response programs.

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.

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.

Customer rates, based upon both forecasted program costs and lost electric revenues and collected via the MEEIA rider, are reconciled annually to actual results.

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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.

Ameren Illinois’ planned investments in electric energy-efficiency programs is approximately $120 million in 2025 and approximately $125 million annually from 2026 to 2029.

Every four years, Ameren Illinois is required to file a four-year electric energy-efficiency plan with the ICC.

In June 2022, the ICC issued an order approving Ameren Illinois’ electric and natural gas energy-efficiency plans for 2022 through 2025, as well as regulatory recovery mechanisms.

The order authorized electric and natural gas energy-efficiency program expenditures of $476 million and $66 million, respectively, over the four-year period.

Ameren Illinois is required to file an updated four-year electric energy-efficiency plan with the ICC by March 2025.

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 based on the annual average of the monthly yields of the 30-year United States Treasury bonds plus 580 basis points.

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 goals.

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 framework.

Ameren Illinois’ natural gas energy-efficiency program costs are recovered through a rider.

Ameren Illinois’ natural gas energy-efficiency program costs are recovered through a separate gas rider.

NATURAL GAS SUPPLY FOR DISTRIBUTION

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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, MoGas Pipeline, and Texas Eastern Transmission Corporation interstate pipeline systems to transport natural gas to their systems.

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.

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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 to capitalize on opportunities to benefit our customers, communities, shareholders, and the environment is driven by the capabilities and engagement of our workforce.

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, Talent, and Rewards, which are discussed further below.

Foundational to our workforce strategy are our core competencies of:

• Be Strategic

• Continuously Improve

• Deliver Results

• Engage Respectfully

• Foster Collaboration

• Think Customer

Ameren’s chief executive officer and 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 human capital matters.

We strive to cultivate a mission-driven, values-based culture that enables the sustainable execution of our core strategy.

We design our human capital management practices and policies to reinforce our values, shape our culture, and drive employee engagement.

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.

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 assess employee engagement through a variety of channels.

As a part of our assessment, we conduct confidential employee engagement surveys to identify areas of strength and opportunities for improvement in our employees’ experience, and take actions aimed at increasing employee engagement.

We also offer flexible work arrangements, such as permitting certain employees to work from alternate locations or to make adjustments to an employee’s daily work hours, among other things, complemented by our work to advance the digital enablement of our workforce, and have enhanced our facilities and workforce policies and practices to increase collaboration and productivity.

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 acts of discrimination.

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.

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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, mentoring and sponsorships, 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, values, strategy and culture, and build leadership skills and capabilities.

In addition, we evaluate our organizational structure and make adjustments and expand roles to facilitate execution of our strategy and organizational efficiency.

In order to attract and retain a skilled and highly qualified workforce, we provide opportunities for employees to expand their knowledge and skill sets, and we support their career development.

Our onboarding efforts are designed to ensure early engagement, including the opportunity to participate in mentoring programs.

Additionally, employees are encouraged to participate in technical, professional, and leadership development opportunities, and outreach initiatives to engage with the communities that we serve, among other things.

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.

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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.

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 attributable to employee retirements, generally allowing for thoughtful workforce and succession planning in advance of these planned transitions.

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:

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Generation Z/Post Millennial (birth years after 1997) 9% 9% 9% 8%

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 the United Government Security Officers of America.

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.

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The Ameren Illinois collective bargaining unit contracts expire in 2027 and 2029, and cover 8% and 92% of represented employees, respectively.

The primary objective of our rewards program is to provide a total rewards package that attracts and retains a talented workforce and reinforces strong performance in a financially sustainable manner.

Management continuously evaluates our core benefits in an effort to create a market-competitive, performance-based, shareholder-aligned total rewards package with a view towards balancing employee value and financial sustainability.

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 pension for substantially all employees and 401(k) savings, 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 strive to provide a competitive and sustainable rewards package that supports our ability to attract, engage, and retain a talented and highly qualified workforce, while at the same time reinforcing and rewarding strong performance.

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

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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, complex new and proposed environmental laws, such as air and water quality standards, mercury emissions standards, limitations on the use of natural gas in generation, CCR management requirements, and potential CO 2 limitations, which may limit, or result in the cessation of, the operation of electric generating units;

• corporate tax law changes, including 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;

• cybersecurity risks, cyber attacks, including ransomware and other ransom-based attacks and those attacks arising from or generated by 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 have increased in frequency and severity within the utility industry, terrorism, and other intentionally disruptive acts;

• 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;

• 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, and managing the impact on customer 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;

• 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;

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• 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;

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

• 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;

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• 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, elevated interest rates, and impacts associated with extended recovery periods from customers;

• 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;

• 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;

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

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• scrutiny by investors and other stakeholders of industry practices;

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

• 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;

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and a director nomination policy that applies to the Ameren Companies.

The information on Ameren’s website, or any other website referenced in this report, is not incorporated by reference into this report.

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.

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