Key Takeaways:

- Ameren Missouri's Integrated Resource Plan outlines the long-term roadmap for meeting customer needs through disciplined scenario planning and investments to cost-effectively keep the lights on for customers.

- The plan optimizes a mix of natural gas, solar, energy storage, fuel cells, wind, nuclear and other technologies to support reliability and stabilize costs under a range of future conditions.

- The plan identifies investments needed to keep energy available when customers need it most.

ST. LOUIS, Sept. 28, 2026 /PRNewswire/ -- Reliable energy service depends on decisions made years before the energy is needed. Through its 2026 Integrated Resource Plan (IRP), Ameren Missouri, a subsidiary of Ameren Corporation (NYSE: AEE), outlines a 20-year energy roadmap for maintaining reliable service and managing costs under a range of customer usage scenarios. Details of the plan are available at AmerenMissouri.com/Reliable.

The IRP reflects several long-term considerations, including forecasted customer energy needs, economic growth, available energy resource technologies and associated costs.

"Our customers depend on us to make thoughtful decisions about the energy system that powers their homes, businesses and communities," said Martin J. Lyons Jr., chairman, president and chief executive officer of Ameren Corporation. "This plan provides a clear path for maintaining reliability, supporting the communities we serve by making the most of existing resources while prudently investing in a mix of additional generation technologies to cost-effectively power the future needs of our customers."

The plan maintains a balanced mix of generation resources, combining existing assets with planned additions to ensure continued reliability. Multiple scenarios were evaluated to help ensure the resource portfolio remains reliable under a range of future conditions.

As part of the IRP, Ameren Missouri identified a portfolio of resources intended to support reliability and customer needs in the years ahead. The preferred plan was selected from more than 20 potential plans. It includes resource additions along with other investments intended to strengthen the energy system and maintain flexibility as future conditions evolve, including:

- Continuing to strengthen reliability through around-the-clock combined-cycle natural gas generation resources, with 2,100 megawatts (MW) scheduled to be in service by 2031, another 2,800 MW by 2035 and a further 1,400 MW by 2042.

- Building 1,900 MW of on-demand simple-cycle natural gas generation resources by 2029, with an additional 2,400 MW after 2040.

- Adding 500 MW of natural gas fuel cells by 2030, a promising and scalable technology that can deliver reliable, on-demand energy at any time of day.

- Supplementing those on-demand generation resources with 1,300 MW of new solar generation resources by 2030 and an additional 2,300 MW by 2045. The plan also calls for the addition of 1,500 MW of wind energy resources after 2030.

- Accelerating and expanding the addition of battery storage, with 2,400 MW planned by 2030, to keep energy available when energy needs are high and customers need it most.

- Planning for 1,200 MW of new nuclear generation by 2040. Although neither a location nor a technology has been selected yet, both advanced large-scale reactor designs and small modular reactors are being considered. Ameren Missouri continues to expect to seek an extension to operate the Callaway Energy Center beyond 2044.

"Reliable service is built on a mix of energy resources that can be called upon under different conditions," said Aaron Melda, chairman and president of Ameren Missouri. "Because no single technology can meet every customer's energy needs on its own, the IRP evaluates how resources can work together to maintain reliability, adapt as customer energy use evolves, and manage costs over time."

Ameren Missouri has committed to serving 2.8 gigawatts of aggregate large-load demand by 2030 through signed electric service agreements, with the potential for additional growth, and this plan accounts for that. State law and the company's Powering Missouri Growth Plan include provisions to ensure these customers cover the costs of the infrastructure needed to serve them, helping protect existing customers while providing reliable service to all.

The IRP is filed with the Missouri Public Service Commission every three years and may be updated more frequently as part of Ameren Missouri's ongoing planning process. The plan evaluates resource options using a broad range of assumptions and scenarios to support sound, long-term decision-making.

About Ameren Corporation

St. Louis-based Ameren Corporation powers the quality of life for 2.5 million electric customers and more than 900,000 natural gas customers in a 67,700-square-mile area through its Ameren Missouri and Ameren Illinois rate-regulated utility subsidiaries. Ameren Illinois provides electric transmission and distribution service and natural gas distribution service. Ameren Missouri provides electric generation, transmission and distribution services, as well as natural gas distribution service. Ameren Transmission Company of Illinois develops, owns and operates rate-regulated regional electric transmission projects in the Midcontinent Independent System Operator, Inc. For more information, visit Ameren.com, or follow us at @AmerenCorp, Facebook.com/AmerenCorp, or LinkedIn.com/company/Ameren. 

Forward-looking Statements

Statements in this release not based on historical facts are considered "forward-looking" and, accordingly, involve risks and uncertainties that could cause actual results to differ materially from those discussed. Although such forward-looking statements have been made in good faith and are based on reasonable assumptions, there is no assurance that the expected results will be achieved. These statements include (without limitation) statements as to future expectations, beliefs, plans, projections, strategies, targets, estimates, objectives, events, conditions, and financial performance. In connection with the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995, Ameren and Ameren Missouri are providing this cautionary statement to identify important factors that could cause actual results to differ materially from those anticipated. The following factors, in addition to those discussed under Risk Factors in Ameren's and Ameren Missouri's Annual Report on Form 10-K for the year ended December 31, 2025, and elsewhere in this release and in our other filings with the Securities and Exchange Commission, could cause actual results to differ materially from management expectations suggested in such forward-looking statements:

- regulatory, judicial, or legislative actions, and any changes in regulatory policies and ratemaking determinations that may change regulatory recovery mechanisms or our ability to recover costs and earn a return, such as those that may result from Ameren Missouri's electric service regulatory rate review filed with the Missouri Public Service Commission (MoPSC) in June 2026;

- our ability to control costs and make substantial investments in our businesses, including our ability to recover costs and investments, and to earn our allowed returns on equity, within frameworks established by our regulators, while maintaining affordability for our customers;

- the effect on Ameren Missouri of any customer rate caps or limitations on increasing the electric service revenue requirement pursuant to Ameren Missouri's election to use the plant-in-service accounting regulatory mechanism;

- Ameren Missouri's ability to construct and/or acquire wind, solar, and other renewable energy generation facilities and battery storage, as well as natural gas-fired and nuclear energy centers, extend the operating license for the Callaway Energy Center, reliably operate existing energy centers through their expected retirement dates, retire fossil fuel-fired energy centers, and implement new or existing customer energy-efficiency programs, including any such construction, acquisition, retirement, or implementation in connection with its Smart Energy Plan, integrated resource plan, or emissions reduction goals, and to recover its cost of investment, a related return, and, in the case of customer energy-efficiency programs, any lost electric revenues in a timely manner, each of which is affected by the ability to timely obtain all necessary regulatory and project approvals, including certificates of convenience and necessity (CCNs) from the MoPSC or any other required approvals, including permits to operate the facilities;

- our ability to realize and support forecasted energy demand and capacity from new and potential new customers, including demand growth dependent on the addition of new data centers and other large primary service customers within our service territories, such as the large load customers that signed electric service agreements with Ameren Missouri in 2026;

- the effects on energy prices and demand for our services resulting from customer growth patterns or usage, including demand from data centers, technological advances, including advances in customer energy efficiency, electric vehicles, electrification of various industries, energy storage, and private generation sources, which are becoming increasingly cost-competitive;

- Ameren Missouri's ability to earn, utilize, or transfer at a reasonable price federal production and investment tax credits related to renewable energy and energy storage projects and nuclear energy production; the cost of wind, solar, and other renewable generation and battery storage technologies; and our ability to obtain timely interconnection agreements with the Midcontinent Independent System Operator, Inc.