Ameren Missouri is developing a new hybrid energy center, the Big Hollow Energy Center, in Jefferson County, Missouri, combining an 800-megawatt natural gas plant with a 400-megawatt battery storage facility.
Ameren Missouri, a subsidiary of Ameren Corporation, announced on June 27, 2025, the filing of an application to the Missouri Public Service Commission for the development of the Big Hollow Energy Center. This groundbreaking facility, located in Jefferson County, Missouri, represents a first-of-its-kind project for the company, integrating an 800-megawatt (MW) simple-cycle Natural Gas energy center with Ameren Missouri's inaugural large-scale battery storage facility.
The Big Hollow Energy Center is strategically designed to address the increasing energy demands of Missouri while simultaneously bolstering grid resiliency. "This is the next step to deliver on our strategy to invest in energy infrastructure for our customers' benefit and provide a balanced generation portfolio," stated Mark Birk, chairman and president of Ameren Missouri.
Similar in design to the existing Castle Bluff Energy Center, the natural gas component of the Big Hollow facility will serve as a crucial backup energy source. It will be capable of delivering power during peak demand periods, such as the coldest winter days and hottest summer afternoons, and will provide essential grid support when renewable energy generation is unavailable.
Co-located with the natural gas plant will be Ameren Missouri's first large-scale Lithium-Ion Battery installation. This planned 400-MW battery storage system is a fast-acting asset, capable of being charged when there is excess energy on the grid and then deployed rapidly to meet customer needs, regardless of weather conditions. A fully charged battery array at Big Hollow could power thousands of homes for several hours, significantly contributing to overall grid reliability, particularly during times of peak energy consumption. This initiative aligns with Ameren Missouri's recently announced acceleration of battery storage capacity, with a target of 1,000 MW by 2030 and a remarkable 1,800 MW by 2042.
A key advantage of the Big Hollow Energy Center is its strategic location on land already owned by Ameren Missouri. This allows the natural gas generation and battery storage facilities to operate independently while leveraging existing energy infrastructure and transmission line access, thereby reducing construction time and costs for customers. Ajay Arora, senior vice president and chief development officer at Ameren Missouri, underscored the importance of a balanced mix of generation technologies and their strategic placement across the region to maximize energy output.
