Missouri approves Ameren’s Big Hollow 800MW gas plant with 400MW co‑located battery

Missouri approves Ameren’s first co-located gas-and-battery plant

Ameren Missouri secures Missouri Public Service Commission approval for the Big Hollow Energy Center, a hybrid facility that pairs an 800-megawatt simple-cycle natural gas plant with a co-located 400-MW lithium-ion battery array in Jefferson County. The commission’s Feb. 11 decision authorizes construction and allows Ameren to leverage existing site access, transmission connections and company-owned infrastructure to shorten permitting and reduce costs to customers. Ameren expects the facility to enter service in 2028 and to provide rapid-response backup during extreme winter and summer peaks while supporting reliability when renewables are unavailable.

The natural gas unit and the battery storage operate independently but are designed to complement one another: the simple-cycle plant supplies sustained megawatt-scale energy during extended demand events, while the battery delivers near-instantaneous support and fast frequency response. When fully charged, the 400-MW battery can power thousands of homes for hours and stabilise system frequency during shortfalls, while the gas turbine provides dispatchable capacity for longer-duration peaks. Ameren frames the configuration as a flexible, dispatchable resource that will support peak capacity, ancillary services and grid stability across its Missouri service territory.

Big Hollow advances Ameren’s broader storage strategy, which targets 1,000 MW of battery capacity by 2030 and 1,800 MW across multiple sites by 2042. Company officials say the hybrid approach improves system flexibility, reduces land use compared with separate sites, and complements ongoing transitions to lower-carbon generation by pairing low-cost renewables with fast-response storage. Ameren highlights the project as part of an integrated generation portfolio aimed at delivering dependable, on-demand power for residential, small business and industrial customers.

Smart Energy Plan shows operational gains

Separately, Ameren Missouri files an updated five-year Smart Energy Plan with the Missouri Public Service Commission on Feb. 12, documenting measurable reliability benefits from recent investments. The company reports upgrades that automatically prevented roughly 160,000 customer outages during major 2025 storms, including about 59,000 outages averted when multiple tornadoes struck on March 14, and cites more than 2,000 smart switches that have helped avoid over 330,000 outages in five years.

Targeted storm hardening and modernization

The plan funds local projects to replace aging poles, wires and substations, and Ameren reports adding 850 composite poles in 2025, storm-hardening more than 300 miles of lines since the Smart Energy Plan began, and modernizing nearly 150 substations. Executives say these targeted investments both limit severe weather impacts and speed restoration, supporting Ameren Missouri’s goal of enhanced reliability and resilience for customers.