ST. LOUIS COUNTY — Ameren received state regulatory approval Wednesday to build a $900 million natural gas power plant in southern St. Louis County and agreed to take some steps that could lead to greater use of wind and solar energy .

The Missouri Public Service Commission, meeting in Jefferson City, unanimously approved an agreement drawn up by the St. Louis-based electric utility and a critic of the new power plant – Renew Missouri, a nonprofit that advocates for increased use of renewable energy became.

“This order is a wonderful compromise because it helps balance our energy portfolio with both traditional and renewable sources,” Commissioner John Mitchell said at the meeting.

PSC members also said the new Castle Bluff power plant, which will replace Ameren’s former coal-fired Meramec Energy Center plant, is needed to address potential power shortages in the St. Louis area and other parts of the state.

“Without this action, customers in this area would incur significant additional costs,” Mitchell said.

Ameren also said the project is necessary to meet increased electricity demand, particularly as data centers and other energy-intensive commercial activities become more important.

“Castle Bluff is an investment in our future,” Jeff Moore, director of combustion turbine generator facilities for Ameren Missouri, said after Wednesday’s decision.

“It will provide essential electrical reliability for our customers, particularly during extreme weather events” when demand is greatest.

He said construction will begin in the next two to three weeks on the site at the confluence of the Mississippi and Meramec rivers. He said the facility should begin operations by the end of 2027.

The agreement calls for Ameren to explore the possibility of purchasing power from Grain Belt Express, a long-planned electric transmission line that would carry power from wind turbines in Kansas through northern Missouri to the Indiana border. Grain Belt is also a party to the agreement approved Wednesday.

The agreement states that Ameren will use “best efforts” to install a battery storage system at one or more of its former coal-fired power plant sites, such as Castle Bluff, by 2027 and 2034.

James Owen, an attorney with Renew Missouri, said such systems are often used to store renewable energy such as wind and solar, although other energy can also be stored.

Owen said because it seemed likely that the state commission would approve the natural gas-fired plant, Renew Missouri thought it made sense to try to make some progress on renewable energy as part of the package.

He said it would “help us digest what we believe was ultimately a poor decision by Ameren” to build a natural gas-fired power plant.

At a virtual public hearing on the issue last month, residents and stakeholders complained about the cost of the plant, the volatility of natural gas prices, the reliability of the fuel source under extreme conditions, the impact on local air quality and how it could exacerbate climate change .

Jason Holsman, one of the PSC members, said at Wednesday’s meeting that while he supports “future clean energy technology,” the state currently has a “resource capacity issue” and renewable energy is being produced intermittently.

He also noted that the new Ameren plant would be built where infrastructure already exists. And he added that natural gas is cleaner than coal.

Ameren has previously said it plans to invest billions in wind and solar projects over the next two decades as the cost of those technologies falls and the utility seeks to reduce and eventually eliminate carbon emissions.

The agreement approved Wednesday also includes other requirements, such as details on how the costs will be factored into Ameren’s rate base.

An attorney for another contracting party, Midwest Energy Consumers Group, could not be reached for comment Wednesday. This organization advocates for large commercial and industrial electricity customers.