The utility plans 1,200 megawatts of new nuclear generation by 2040 and the retirement of all coal units by 2042.

Ameren Missouri, a unit of Ameren Corp. (NYSE: AEE), plans to add 1,200 megawatts of nuclear generation by 2040 while expanding gas, solar, wind and battery capacity, according to a 20-year plan filed with the Missouri Public Service Commission on Sept. 28.

rThe plan schedules all coal-fired capacity to retire by 2042 and comes as the utility forecasts faster growth in electricity demand than it anticipated in its previous plan.

Ameren Missouri phases in gas generation

Ameren Missouri plans 1,900 megawatts of simple-cycle gas capacity by 2029 and another 2,400 MW after 2040. Combined-cycle plants would add 2,100 MW by 2031, another 2,800 MW by 2035 and 1,400 MW by 2042. The plan also includes 500 MW of natural gas fuel cells by 2030.

Two 800-MW simple-cycle plants are under construction: Castle Bluff, scheduled for completion by the end of 2027, and Big Hollow, which is scheduled to enter service by the end of 2028.

The 2,100-MW West Alton combined-cycle plant, next to the Sioux Energy Center, is planned to enter service in three units during 2031, with the first unit scheduled for the second quarter.

Solar, wind and batteries capacity also expands

The plan calls for 1,300 MW of new solar generation by 2030, bringing total solar capacity to approximately 2,200 MW. Another 2,300 MW is planned by 2045, taking total of 4,500 MW.

The plan also calls for 1,500 MW of wind after 2030, bringing total wind capacity to 2,200 MW, and 2,400 MW of battery storage by 2030.

Ameren Missouri says accelerating solar and battery projects would allow it to capture available federal tax credits and pass the resulting savings to customers.

Nuclear site or technology have not been selected

Ameren Missouri is considering advanced large-scale reactors and small modular reactors for the 1,200 MW of nuclear capacity. Its 2025 plan called for 1,500 MW, but the utility reduced the target to reflect the potential use of different reactor technologies, according to the filing.

The company says supportive state and federal policy will remain critical to new nuclear development. It also seeks an extension of the Callaway nuclear plant's operating license beyond 2044.

Ameren Missouri chose the plan from more than 20 alternatives. Levelized average rates over the 20 years are about 5% higher under the plan than under an alternative without new nuclear, the plan says. The annual difference does not appear until 2040.

Two labadie coal units get later retirement dates

Ameren Missouri's 2023 plan assumed two of the four Labadie units would retire in 2036. The new plan moves those retirements to 2042, when the other two units are already scheduled to retire.

The Sioux Energy Center is scheduled to retire by the end of 2035. Coal currently accounts for the largest share of the energy generated by the company, and the plan says retaining some coal capacity alongside new generation will support reliability.

Large customers demand forecasts rise

Ameren Missouri has signed electric service agreements since the start of 2026 representing 2.8 gigawatt of expected demand by 2030. Its 2025 plan reflected 1.5 gigawatts of expected large-customer demand by 2032.

The new plan forecasts large-customer demand of approximately 2.9 GW by 2030, 5 GW by 2035 and 6 GW by 2046. Under its high-demand scenario, those figures rise to 3.9 GW by 2030 and 9 GW by 2046.

The company expects base customer sales to rise 60% from 2027 to 2030

The utility says state law and its Powering Missouri Growth Plan include provisions to ensure data centers cover the cost of infrastructure built to serve them.

Sierra club criticizes coal delays and gas additions

Jenn DeRose, the group's Beyond Coal campaign strategist in Missouri, described the plan "pollution-heavy" in a statement. Sierra Club said the planned gas investments will worsen local climate disasters.

Regulators weigh Ameren Missouri projects

Projects require certificates of convenience and necessity from the commission. Ameren Missouri plans to seek additional certificates over the next three years for gas, battery, solar and fuel cell projects.

The commission has approved 400 MW of battery storage at Big Hollow and the 250-MW Reform solar project in Callaway County. Ameren Missouri expects approval of pending battery applications in the fourth quarter of 2026.

According to the plan, applications remain pending for the 2,100-MW West Alton combined-cycle plant, filed in July 2026; 545 MW of battery storage at Castle Bluff, Huck Finn and Millcreek; and the 175-MW Tom Sawyer and 225-MW Ringer solar projects.