Ameren Missouri has received approval from the Missouri Public Service Commission to develop the Big Hollow Energy Center, Missouri’s first integrated natural gas and battery storage facility, the company said.

The project will combine an 800-megawatt simple-cycle natural gas energy center with a 400-megawatt lithium-ion battery storage system at a single site in Jefferson County, Missouri. The facility will be integrated into Ameren Missouri’s statewide generation system and is intended to support electric reliability for residential, small business and industrial customers across the company’s service territory.

With regulatory approval in place, Ameren Missouri expects the Big Hollow Energy Center to begin serving customers in 2028. The company said the natural gas portion of the project will operate during periods of peak demand, including extreme winter and summer conditions, and will provide backup support to the grid when other generation resources are unavailable.

Battery storage

The battery storage component will be Ameren Missouri’s first large-scale lithium-ion installation. The 400-MW system is designed to respond within moments to support customer energy needs and, when fully charged, could power thousands of homes for several hours, according to the company. Ameren Missouri plans to add 1,000 MW of battery storage by 2030 and a total of 1,800 MW across multiple sites by 2042.

The natural gas and battery storage facilities will operate independently while using existing energy infrastructure already owned by Ameren Missouri, which the company said is expected to reduce construction time and costs to customers.

“Today’s decision allows us to advance an investment that supports reliability for all of our customers,” said Michael Moehn, group president of Ameren Utilities at Ameren Corporation. “Big Hollow will be part of the generation system that serves homes, businesses and communities across Missouri.”

Ameren Missouri is a subsidiary of Ameren Corporation.

The Big Hollow Energy Center will be built at the former Rush Island Energy Center site in Jefferson County, Missouri, and will connect to Ameren Missouri’s 345-kilovolt transmission system. The Missouri Public Service Commission granted Certificates of Public Convenience and Necessity for the project, authorizing Ameren Missouri to move forward with construction of both the natural gas and battery storage facilities.

Under the Commission’s approval, Ameren Missouri must submit quarterly progress reports on the project, document any investment tax credits claimed under the federal Inflation Reduction Act, and notify the Commission if project costs change by more than 15 percent.

Missouri’s evolving energy mix

The Big Hollow Energy Center joins other significant energy developments in Missouri, including the Kelso Solar Project in Scott County. The utility-scale solar project, currently under construction, will deliver 430 megawatts of renewable capacity and is expected to begin commercial operations by the end of 2025. Once complete, Kelso will contribute to Missouri’s growing solar capacity while supporting local employment and community revenues.

Big Hollow Energy Center: Project Factsheet

Overview

• Missouri’s first integrated natural gas and battery storage facility
• Location: Jefferson County, Missouri
• Owner/Operator: Ameren Missouri (subsidiary of Ameren Corporation)
• Expected operational: 2028
• Regulatory approval: Missouri Public Service Commission

Project Specifications

• Natural Gas Plant: 800 MW simple-cycle capacity
• Battery Storage: 400 MW lithium-ion system (Missouri’s first large-scale installation)
• Total Capacity: 1,200 MW hybrid facility
• Service Area: Statewide – residential, business, and industrial customers

Project Team

• Ameren Missouri – Project owner and operator
• Ameren Corporation – Parent company
• Missouri Public Service Commission – Regulatory authority (approval granted)

Key Features

• Rapid-response backup power during peak demand periods
• Battery system responds within moments to grid needs
• Designed for extreme weather (coldest winter days, hottest summer afternoons)
• Supports renewable energy by providing backup when renewables are unavailable
• Leverages existing infrastructure to reduce costs and construction time
• Natural gas and battery systems operate independently

Timeline & Expansion Plan

• 2025-2028: Construction phase
• 2028: Expected operational date
• 2030: 1,000 MW total battery storage target (Ameren Missouri)
• 2042: 1,800 MW total battery storage across multiple sites

Strategic Benefits

• First-of-its-kind hybrid facility in Missouri
• Enhanced grid stability and reliability statewide
• Supports growing energy demand while maintaining service reliability
• Part of Ameren Missouri’s grid modernization strategy
• When fully charged, batteries can power thousands of homes for hours