Archive · 18 Sep 2026
Extreme Heat Strains North American Power Grids During Maintenance
Very hot weather makes people use more electricity for air conditioning.
At the same time, many power plants are turned off for planned repairs.
This is happening across power grids serving more than 100 million people.
The Midcontinent Independent System Operator had about 51 gigawatts of power generation offline.
PJM also had nearly 37 gigawatts offline while electricity use was expected to exceed 132 gigawatts.
PJM asked some large customers to use less electricity.
The United States Department of Energy also approved backup generators and considered allowing some plants to operate under relaxed emissions rules.
Experts said aging equipment, growing data-center demand and unusual weather are making it harder to find a quiet season for repairs.
Power grids serving more than 100 million North Americans face a demand surge amid unusually hot weather.
MISO reported about 51 gigawatts of generation outages while demand was forecast to reach 105.2 gigawatts.
PJM expects usage above 132 gigawatts, with nearly 37 gigawatts of generation offline.
PJM ordered some major non-residential customers to reduce consumption and sought temporary emissions-rule relief.
High demand, aging plants, data-center growth and shrinking maintenance windows are increasing pressure on the grid.
- Who
- Power-grid operators including the Midcontinent Independent System Operator and PJM Interconnection, along with the United States Department of Energy.
- What
- Extreme heat is driving electricity demand while substantial generation capacity is offline for scheduled maintenance.
- When
- The strain was reported Wednesday and Thursday, with triple-digit temperatures forecast through at least Sunday.
- Where
- Power grids across parts of the United States, including areas around St. Louis, Chicago, Washington, Virginia, Ohio, Kentucky and western Pennsylvania.
- Why
- Unseasonable heat, planned plant maintenance, aging generating stations, industrial growth and rising data-center demand are reducing available power reserves.
- Population affected
- Power grids serving more than 100 million North Americans are preparing for higher demand.
- MISO outages
- About 51 gigawatts of generation were offline Thursday, while demand was forecast at 105.2 gigawatts.
- PJM demand
- PJM expected electricity usage to surpass 132 gigawatts.
- PJM outages
- Nearly 37 gigawatts of generation were offline.
- Weather
- Some areas served by MISO were more than 20°F above normal; St. Louis was forecast to reach 99°F.
- Emergency measures
- PJM requested emissions-rule relief, and the United States Department of Energy authorized backup generation resources.
- Price spike
- Spot power prices exceeded $4,300 per megawatt-hour at the benchmark Western hub shortly after 6 p.m. Wednesday.