Ameren Corporation (Ameren) operates as a public utility holding company. Ameren's principal subsidiaries are Ameren Missouri, Ameren Illinois, and ATXI. Ameren also has other subsidiaries that conduct other activities, such as providing shared services.
Ameren Missouri (Union Electric Company and its subsidiary, Ameren Missouri Securitization Funding I, LLC (AMF)) operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distributio...
Ameren Corporation (Ameren) operates as a public utility holding company. Ameren's principal subsidiaries are Ameren Missouri, Ameren Illinois, and ATXI. Ameren also has other subsidiaries that conduct other activities, such as providing shared services.
Ameren Missouri (Union Electric Company and its subsidiary, Ameren Missouri Securitization Funding I, LLC (AMF)) operates a rate-regulated electric generation, transmission, and distribution business and a rate-regulated natural gas distribution business in Missouri.
Ameren Illinois (Ameren Illinois Company, an Ameren Corporation subsidiary that operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois, doing business as Ameren Illinois) operates rate-regulated electric transmission, electric distribution, and natural gas distribution businesses in Illinois.
ATXI (Ameren Transmission Company of Illinois) operates a FERC rate-regulated electric transmission business in the MISO.
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 Ameren Transmission Company of Illinois, an Ameren Corporation subsidiary that operates a FERC rate-regulated electric transmission business in the MISO (ATXI).
Ameren Missouri has one segment. Ameren Illinois has three segments: Ameren Illinois Electric Distribution, Ameren Illinois Natural Gas, and Ameren Illinois Transmission.
Regulation
The MoPSC regulates rates and other matters for Ameren Missouri. The Illinois Commerce Commission(ICC) regulates rates and other matters for Ameren Illinois. The Missouri Office of Public Counsel (MoPSC) and the ICC regulate non-rate utility matters for ATXI.
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.
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.
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.
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. 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.
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 7,560 MWs in 2024. 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 8,479 MWs in 2024. 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.
Supply Of Electric Power
Capacity
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
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. 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;
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 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 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. 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.
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 federal administration, and state renewable energy requirements, which could lead to the retirement of baseload assets before the end of their 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 requires Ameren Missouri to offer net metering to certain customers that install renewable generation at their premises.
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 2024, 2023, and 2022, Ameren Illinois procured power on behalf of its customers for 25%, 28%, and 28%, respectively, of its total kilowatt hour 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 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 the CEJA, 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. 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. 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, 2024, Ameren Missouri’s coal-fired energy centers represented 6% 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. 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.
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 10.7 million tons of coal in 2024.
About 97% 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.
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 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.
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, 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.
History
Ameren Corporation was founded in 1881. The company was incorporated in 1995.
