AMEREN CORP

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 7,836 MWs in 2023. The AMIL balancing authority area includes the load of Ameren Illinois and certain natural gas-fired energy centers of Ameren Missouri, and had a peak demand of 8,859 MWs in 2023. 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. In July 2022, the ICC issued an order requiring Ameren Illinois to perform a cost-benefit study of continued participation in the MISO compared to participation in PJM Interconnection LLC, another RTO. In July 2023, Ameren Illinois filed its cost-benefit study with the ICC. The study concluded that continued participation in the MISO was prudent and more cost-beneficial than participation in PJM Interconnection LLC. In January 2024, the ICC staff submitted a report recommending the ICC not take any action with regard to changing Ameren Illinois’ RTO membership. The ICC is under no obligation to issue an order related to the cost-benefit study. For additional information regarding the RTO cost-benefit study, see Note 2 – Rate and Regulatory Matters under Part II, Item 8, of this report.