Ameren Missouri's Big Hollow hybrid approved: 800MW gas plus 400MW battery to boost reliability

Big Hollow hybrid plant cleared to boost Missouri reliability

Ameren Missouri wins Missouri Public Service Commission approval on Feb. 11, 2026 to build the Big Hollow Energy Center, a hybrid generation site pairing an 800-megawatt simple‑cycle natural gas plant with the state’s first co‑located large‑scale 400‑MW lithium‑ion battery array in Jefferson County. The facility is designed to strengthen reliability for residential, small business and industrial customers across Ameren’s service territory and is scheduled to begin serving in 2028. Ameren integrates Big Hollow into its statewide generation portfolio and leverages existing company‑owned infrastructure to shorten construction timelines and limit costs to customers.

The two resources at Big Hollow operate independently but are engineered to complement one another: the simple‑cycle plant provides sustained megawatt‑scale output during extended peak demand, while the 400‑MW battery delivers near‑instantaneous support for frequency stabilization and shortfalls. When fully charged, the battery can power thousands of homes for hours and supply fast response during the coldest winter days and hottest summer afternoons or when renewable output is limited. The commission’s authorization enables Ameren Missouri to capitalize on existing site access, transmission connections and operational expertise to streamline permitting, minimize land use and control capital expenditure.

Big Hollow forms a central piece of Ameren’s broader battery strategy to add 1,000 MW of storage by 2030 and reach 1,800 MW across multiple sites by 2042. Company planners say the hybrid approach enhances system flexibility and provides a dispatchable resource able to support peak capacity needs, ancillary services and rapid frequency response while complementing the utility’s transition to a cleaner generation mix. Regulators and company officials frame the project as a way to balance on‑demand reliability with integration of lower‑cost renewables across Missouri.

Smart Energy Plan underlines storm resilience

Ameren Missouri files an updated five‑year Smart Energy Plan on Feb. 12, 2026 that documents measurable customer benefits from recent grid investments, saying upgrades automatically prevented about 160,000 customer outages during major 2025 storms, including roughly 59,000 outages avoided when a dozen tornadoes struck on March 14. The filing highlights more than 2,000 smart switches now monitoring the grid 24/7 that have helped prevent over 330,000 outages in five years.

Local grid hardening and operational gains

The plan funds targeted local projects to replace aging poles, wires and substations, with Ameren adding 850 composite poles in 2025, storm‑hardening more than 300 miles of lines since the program began and modernizing nearly 150 substations to improve reliability and capacity. Company leaders stress these measures reduce customer minutes of interruption, accelerate restoration and guide capacity planning alongside new generation investments.