Quick answer
The biggest recent Illinois outages came from summer storms: the August 2020 derecho cut power to more than 800,000 ComEd customers, and June 2026 storms hit about 684,000. Ameren's largest was the June 2023 derecho, at more than 225,000. ComEd's grid is more reliable on normal days, but 2026 brought it more major storms than any year in two decades.
What were the biggest Illinois power outages since 2020?
| When | Utility | Customers who lost power | Hit hardest |
|---|---|---|---|
| Aug. 10, 2020 derecho | ComEd | More than 800,000 at one point | Chicago area |
| Feb. 22-23, 2023 ice storm | ComEd | About 231,000 | McHenry, Winnebago and Kane counties |
| June 29, 2023 derecho | Ameren | More than 225,000 over three days | Macon, Champaign and Vermilion counties |
| July 15, 2024 storms | ComEd | More than 440,000 | Chicago area |
| June 2026 storms | ComEd | About 684,000 over two days | Northern Illinois |
| June 2026 storms | Ameren | 88,000 restored by June 19 | Galesburg, Monmouth, Decatur, Effingham, Mattoon and Charleston were last |
| Aug. 11-12, 2026 storms | ComEd | About 410,000 | Southwest suburbs |
| Aug. 13-15, 2026 storms | Ameren | Up to about 26,000 | Bloomington-Normal |
ComEd's chief operating officer called the June 2026 storms the worst damage since the 2020 derecho. Town pages list local outages where we could source them, for example McHenry in the 2023 ice storm, Belleville in June 2026 and Bloomington in August 2026.
Is 2026 a record storm year for ComEd?
Yes, by ComEd's own count. ComEd called the August 11-12, 2026 storms its 20th major weather event of the year, the most it had seen in more than two decades, and those storms alone caused about 410,000 customer outages. Ameren Illinois also had repeated storms across central Illinois in June and August 2026.
Is the Illinois power grid getting more reliable?
On ordinary days, yes. ComEd says a 2025 benchmarking study ranked it No. 1 among similar utilities for how rarely and how briefly customers lose power, with outage frequency more than 50% better than in 2012. Those gains matter most for small, everyday outages. Severe storms that bring down trees and poles still cause widespread outages that can last a day or more, as 2026 showed.
State rules require ComEd and Ameren to file yearly reliability reports with the Illinois Commerce Commission, which reviews each utility's performance at least every three years and makes the reports public. Since 2022, the utilities also face performance metrics on reliability, with penalties that reduce their profits if they fall short, according to the Citizens Utility Board.
How do I keep my power on during the next big storm?
- A home battery switches on in a fraction of a second and, with solar, can recharge during a multi-day outage. ComEd and Ameren pay about $300 per kWh toward one. See what a home battery can run.
- A standby generator runs as long as it has fuel. See generator vs. battery.
- Protect the basement. Storms that cut power often bring heavy rain. See battery backup for a sump pump.
- On a private well? No power means no water. See battery backup for well water.
Solar panels alone shut off in an outage for safety; it takes a battery to keep power on. See does solar work in a power outage?
Sources
- ABC7 Chicago: August 2020 derecho outages
- Northern Public Radio: Thousands without power after freezing rain (Feb. 2023)
- Ameren Illinois: Recognized for derecho power restoration (Jan. 2024)
- ComEd: Power restored for more than 350,000 customers after extreme storms (July 2024)
- ComEd: June 2026 storm restoration
- Ameren Illinois: Storm update (June 19, 2026)
- ComEd: Restores power after Aug. 11-12, 2026 storms
- Ameren Illinois: Storm communications update (Aug. 14, 2026)
- ComEd: No. 1 in U.S. for reliable service, benchmarking shows (Nov. 2025)
- 83 Ill. Adm. Code 411.140: Commission review of reliability reports
- Citizens Utility Board: ICC sets utility performance metrics (Sept. 2022)
- ComEd: Distributed generation and storage rebates
This guide is general information, not tax, legal or financial advice. Incentive programs change, so confirm current terms with your installer, your utility and a tax professional.