Ameren and the bi-state grid linking Missouri and Illinois
Ameren is one of the largest investor-owned utilities in the Midwest, serving Missouri and Illinois through two regulated subsidiaries: Ameren Missouri and Ameren Illinois. The company is rolling out a multi-year Smart Energy Plan that has automatically prevented hundreds of thousands of customer outages over the past five years.
- The size of the Ameren network and the regions it covers
- Why power outages happen on the Ameren grid
- The Smart Energy Plan and the MISO Tranche 2.1 transmission projects
- How smart switches and composite poles are reshaping reliability
2.4 million electric customers across a 64,000-square-mile territory
Ameren operates two regulated utility subsidiaries. Ameren Missouri provides electric generation, transmission and distribution and natural gas distribution in Missouri. Ameren Illinois provides electric transmission and distribution and natural gas distribution in central and southern Illinois.
- About 2.4 million electric customers across Missouri and Illinois.
- More than 900,000 natural gas customers.
- 64,000 square miles of service territory.
- Up to 40% improvement in reliability on circuits with the most advanced smart grid upgrades.
Ameren Corporation (NYSE: AEE) is headquartered in St. Louis. Ameren Missouri is regulated by the Missouri Public Service Commission and Ameren Illinois by the Illinois Commerce Commission.
Why tornadoes, derechos and ice storms hit Ameren's lines
The Missouri and Illinois territories sit in the heart of the U.S. severe weather corridor, with thunderstorms, tornadoes, ice storms and high heat all driving outages. The 2025 storm season included a dozen tornadoes touching down on March 14 alone.
Severe weather and tornadoes
Both states sit on the eastern edge of Tornado Alley. Tornadoes, derechos and intense thunderstorms cause most large-scale outages, sometimes spread across hundreds of miles in a single event.
Ice storms
Winter ice storms cause some of the longest restoration events on the Ameren grid, with ice accumulation on conductors and broken tree limbs combining to take down both transmission and distribution circuits.
Trees and vegetation
Tree contact remains a major day-to-day cause of unplanned power outages, particularly in the more wooded eastern Missouri and southern Illinois territories.
Aging infrastructure
Older wood poles, conductors and substation equipment fail more often. Replacement and modernization is one of the largest line items in the Smart Energy Plan.
The Smart Energy Plan and 330,000 outages avoided in five years
Ameren Missouri filed an updated Smart Energy Plan with the Missouri Public Service Commission in February 2026, outlining a five-year strategy to advance a stronger, more resilient electric grid.
Ameren Smart Energy Plan results
About 160,000 customer outages automatically prevented during 2025 storms.
More than 330,000 customer outages avoided over the past five years thanks to smart grid devices.
59,000 outages prevented during the March 14, 2025 tornado outbreak alone.
More than 2,000 smart switches monitoring the grid 24/7.
850 composite poles installed in 2025 alone.
About $1.3 billion of new MISO Tranche 2.1 transmission projects awarded to Ameren in 2025.
Construction also began at the Castle Bluff Energy Center, an 800 megawatt quick-start natural gas facility designed to support the grid during periods of high demand and to back up renewables.
Smart switches, composite poles and Castle Bluff energy center
Smart switches and self-healing
More than 2,000 smart switches automatically isolate damaged sections and reroute power to as many customers as possible. The technology has produced up to 40% fewer outages on circuits where it has been deployed alongside other Smart Energy Plan upgrades.
Composite poles
Composite poles are stronger than wooden ones, resist rot and woodpecker damage and help speed restoration by preventing cascading damage to overhead lines. 850 new composite poles were installed across the Missouri territory in 2025.
MISO Long-Range Transmission Plan
Ameren is leading approximately $1.3 billion of new transmission projects in MISO's Tranche 2.1 portfolio. The energy corridors carry clean energy across Missouri, Illinois and several Midwest states and add bulk-power resilience for the bi-state region.
Balanced generation portfolio
Ameren Missouri operates the Callaway nuclear energy center along with hydro, solar and wind. New natural gas peakers and battery storage support the grid during high demand and back up renewables.
Ameren outage map and customer assistance
Ameren outage map
Ameren publishes a public outage map updated in near real-time, with separate views for Ameren Missouri and Ameren Illinois. Customers can search by address or zip code and follow estimated restoration times.
Mobile app and alerts
The Ameren mobile app gives access to the outage map, lets customers report a power outage and pushes proactive SMS, email and app notifications when service is interrupted.
Bill assistance and energy efficiency
Ameren runs energy efficiency rebates, weatherization assistance for income-eligible customers, plus partnerships with state programs (LIHEAP, Illinois LIHEAP) and non-profits.
Evergy and Missouri/Illinois ISPs
For a wider view of how the U.S. electric grid works and why outages happen, see the U.S. power outage page. The other major utility serving Missouri and Kansas is Evergy. For internet outages across the same Missouri and Illinois footprint, the most common providers are Spectrum, AT&T and Xfinity.