The Missouri Public Service Commission unanimously approved a settlement agreement on rates for Ameren’s large load customers that insulates ratepayers from most costs associated with supplying data centers’ electricity needs.
The plan defines large load customers as those requiring a maximum 75 MW or more in monthly demand. Supply contracts under the rate would have minimum 12-year terms, with an option for a five-year load ramp period, making for potential 17-year contracts. The PSC sanctioned the rate Nov. 24 (ET-2025-0184).
Agreements would automatically extend for five-year increments unless customers provide a 36-month written notice that they intend to end or reduce their service. Customers who elect not to extend their service must pay exit and early termination fees.
Large load facilities would be required to post collateral equal to two years of minimum monthly bills. Under the plan, they would be able to participate in Ameren’s nuclear and clean energy programs through an expanded clean energy choice rider.
The rate also stipulates that a percentage of excess revenues from large customers be dispersed to benefit ratepayers, with half of the revenues earmarked for low-income customers. Finally, Ameren must evaluate the cost allocations for large loads and ensure that existing customers aren’t paying for costs that should be paid by data centers and manufacturers.
The Missouri PSC said its approval of the agreement is “a significant step forward in implementing” 2025’s Senate Bill 4. The omnibus energy bill enacted by the state legislature prevents large customers’ “unjust or unreasonable” costs from bleeding into other customers’ bills, among other directives.
“Efforts were also made to design a plan that was similar to other tariffs throughout the country, and across Missouri, ensuring Missouri can properly compete for the economic development benefits that these loads represent,” the PSC said in a press release.
Several parties signed off on the settlement agreement, including Ameren, the PSC staff, Google, Sierra Club, Missouri Industrial Energy Consumers, Renew Missouri and Evergy.
The PSC’s vote enshrined more consumer protections than originally were drawn up in the large load rate; an earlier version applied the rate to customers of 100 MW and above and included a 10-year contract term.
Jenn DeRose, a strategist with the Sierra Club’s Beyond Coal Campaign in Missouri, said the rate plan is a “step in the right direction” to protect ratepayers from cost increases from data centers and discourage speculative moves from developers.
“Missourians are rightly concerned about the impacts of new data centers on their electric bills and communities, and they deserve protections,” DeRose said in a statement. “How will customers be protected after Ameren spends billions of dollars of our money on new gas-burning power plants if the AI bubble bursts, the utility overbuilds power plants due to AI speculation, or AI data centers become significantly more efficient?”
Senate Bill 4 also requires utilities to replace retiring plants with dispatchable resources and mandates that utilities source at least 80% of their capacity with dispatchable generation.
That means large loads in Missouri likely would take a lot of natural gas-fired power. Ameren Missouri is planning a significant gas expansion, including the Castle Bluff Energy Center anticipated in 2027 and the Big Hollow Energy Center in 2028. The utility’s 2025 preferred resource plan includes building 1.6 GW of new natural gas generation by 2030 and a total 6.1 GW by 2045. Ameren Missouri’s next integrated resource plan filing is due to the commission in 2026.
