Unseasonable Heat Strains Power Grids Serving 100 Million Across North America

Power grids supplying more than 100 million people across North America are straining under a surge in demand brought on by unusually high temperatures, forcing operators to postpone maintenance and seek emergency measures.

In some areas covered by the Midcontinent Independent System Operator (MISO), temperatures are running more than 20F (11C) above normal. The US National Weather Service forecasts triple-digit heat across the South through at least Sunday. St. Louis is expected to reach 99F (37C) — roughly 18F above the seasonal norm — and remains under a heat advisory through late Saturday.

The neighbouring grid managed by PJM Interconnection, which spans Chicago, Washington DC and Virginia's Data Center Alley, issued an alert that reserve power supplies are under pressure in some areas and directed several large non-residential customers to reduce consumption.

The heat arrived just as plant operators had scheduled autumn maintenance. MISO reported about 51 gigawatts of generation offline on Thursday, even as demand was projected to hit 105.2 gigawatts. PJM expects usage to exceed 132 gigawatts, with nearly 37 gigawatts unavailable.

PJM asked the US Department of Energy on Wednesday to waive certain emissions rules so plants could run at full capacity, and the agency authorised the deployment of backup generation resources on Thursday to head off potential shortages. Spot power prices on the largest US grid climbed above $4,300 per megawatt-hour at the benchmark Western hub shortly after 6 p.m. local time on Wednesday.

The strain follows a summer of extreme heat that repeatedly forced federal orders for plants to operate at maximum output, adding pressure to a system already coping with rising industrial and data-centre demand. Gary Cunningham, a director at Tradition Energy, said PJM's generation fleet "is starting to show signs of its age when trying to stay working," and added that wholesale power prices are likely to remain elevated across Virginia, Ohio, Kentucky and western Pennsylvania through Thursday.

Autumn is normally an ideal window for maintaining power equipment as milder weather reduces air-conditioning use. But erratic conditions linked to climate change and natural phenomena such as El Niño are compressing that repair calendar. The artificial intelligence boom is also lifting overall electricity demand, leaving critical equipment with little downtime. Cunningham noted that unseasonable weather "plays well into the narrative of PJM needing more generation capacity, and needing it NOW, even before new demands to meet data center requirements come."