By Jonathan Kim on August 19, 2025
Ameren Missouri is citing a new law that it backed to justify building a methane gas plant that could increase costs for residential customers.
The St. Louis–based monopoly utility invoked Senate Bill 4 (SB 4), the omnibus energy bill passed in April 2025, multiple times in testimony with the Missouri Public Service Commission (MPSC). The filings outline Ameren’s proposed “Big Hollow” project that includes an 800 MW methane gas plant and 400MW of battery storage – one Ameren says will help it comply with provisions in SB4, a law for which it lobbied, and which passed over the objections of consumer and environmental advocates this year.
SB 4 was the signature utility and energy legislative bill passed under first-year Governor Mike Kehoe. Ameren lobbied for the package, and its lobbyists reportedly shaped substantial portions of the bill. Ameren also donated $215,000 to Kehoe’s gubernatorial campaign. Consumer advocates warned that the legislation could raise customer bills more than $1,000 annually and environmental organizations raised alarms over the preference the bill gives to methane gas.
To justify a gas plant buildout, Ameren is relying on specific provisions in SB4 that require utilities to replace retiring plants with “dispatchable” resources – or generation that can be turned on or ramped up on demand, such as methane gas plants – and that dispatchable resources comprise at least 80% of a utility’s capacity. In seeking regulatory approval for Big Hollow, Ameren argues that the project will enable it to meet “the letter and spirit of the replacement generation requirement.” Multiple times throughout its MPSC filings, Ameren cites adherence to the rule it helped create as a benefit of the project.
The requirements favoring dispatchable resources are likely to raise costs for customers. By requiring such high proportions of generation resources for utilities to be “dispatchable,” SB 4 also limits the amount of utility-scale renewable generation that utilities can construct — generation that is often a cheaper alternative to fossil fuels.
Missouri currently has relatively low renewable energy penetration — renewables provide about 12% of electricity generation, suggesting its grid could accommodate far more with little concern for the portfolio’s overall reliability. Neighboring states of Kansas and Iowa generate 46% and 55% of their electricity from intermittent renewable energy sources, respectively.
Ameren also asserts that it could fall out of compliance with the requirement to have 80% dispatchable resources if the MPSC does not allow it to build the new methane gas plant. Specifically, Ameren said that if it does not receive approval for Big Hollow’s methane gas plant and either an additional future planned gas plant is delayed or its Labadie coal plant retires earlier than 2036 — possibilities Ameren believes to be “real concerns” — then Ameren will be out of compliance with the law that it lobbied for.
The MPSC is likely to decide in early 2026 whether to allow Ameren to move forward with the Big Hollow project, based on a proposed procedural schedule.
Consequences for customers and rates
The primary rationale that Ameren gives for needing Big Hollow is the projection of growth in demand from new large load customers, part of a national trend of data center growth that is driving up electricity prices for customers across the country. Ameren claims that it has 2.3 GW of signed construction agreements for data centers.
But despite Big Hollow ostensibly being built for these prospective large-load customers, Ameren plans to charge all customers for building generation to serve that new load. While Ameren argues that meeting the reliability requirements of SB 4 — including the “dispatchable” requirements and additional resource adequacy provisions — benefits all customers, building a new gas plant will result in higher bills. It’s not clear that the new plant would be necessary to serve existing customers without the requirements of SB 4 or new load.
Ameren Missouri customers are already struggling with rising bills. Nearly 200,000 customers were behind on their bills in July, owing more than $30 million combined. Over the past year, Ameren Missouri has shut off power for more than 100,000 customers who were unable to pay, including one customer who died in her home when a heat wave set in. A group of advocates recently protested Ameren restarting disconnections in areas affected by tornadoes in May.
While the MPSC has yet to make its formal decision on the Big Hollow proposal, its chair has signaled support for the provisions in SB4 that Ameren Missouri is using to make its case. MPSC Chair Kayla Hahn is supportive of data center load growth in the state and lobbied for provisions of SB 4, in an unusual show of political advocacy for a utility regulator. Hahn has also expressed skepticism that renewable generation is cost-effective for customers, despite more than a decade of evidence showing it is.
