Energy Dept Pulls Data Centers Off the Grid as Heat Wave Peaks
As a heat dome pushed demand toward a grid record, Washington ordered data centers off the public network and onto their own generators, freeing up power to keep home air conditioners running.
Energy Secretary Chris Wright told data centers across 13 mid-Atlantic states this week to run on their own generators instead of drawing from the public grid, freeing up capacity so residential air conditioners could keep running through the worst of this week's heat.
The order landed as the heat index topped 100 degrees by 10 a.m. Thursday in every major metro from Washington to New York, and it targets the grid operator PJM, the country's largest, spanning 13 states and Washington, D.C., and home to Virginia's cluster of data centers, the largest concentration in the world. Wright's directive lets PJM require data centers and other heavy electricity users to switch to backup power as a last resort before blackouts.
"Maintaining affordable, reliable, and secure power in the PJM service territory is non-negotiable."
Chris Wright, U.S. Energy Secretary
The math behind the order is the interesting part. The Energy Department estimates there are more than 35 gigawatts of backup generation sitting unused nationwide, enough, using standard household-load assumptions, to power roughly 26 million homes. Tapping even a slice of that lets utilities avoid rationing power to actual households during a heat wave that the National Weather Service says will push temperatures to 95-105 degrees through the July 4 weekend. PJM had projected demand would peak Wednesday at about 166,147 megawatts, within reach of the grid's all-time summer record, set in 2006.
New York City isn't even part of PJM's territory, and it had its own trouble Thursday: more than 15,000 Con Edison customers across the city and areas farther north lost power amid the heat, according to the utility's outage map. Mayor Zohran Mamdani asked residents on social media to help anyway.
Post by @NYCMayor
City buildings are holding to the same 78-degree rule Mamdani asked of residents, with lights dimmed during peak demand hours and non-essential equipment powered down, his office said. The ask has precedent. Predecessors including Bill de Blasio and Eric Adams made near-identical requests during past heat waves, and the Department of Energy itself lists 75 to 78 degrees as the efficiency sweet spot for home air conditioning.
What the backup-generator order doesn't solve is the emissions math. Many of the large generators data centers keep on hand run on diesel or gas, and are dirtier and less efficient than the utility-scale plants they're replacing for a few days. Communities near data centers get the exhaust; the wider PJM grid gets the relief. The region also has fewer large batteries than states like Texas and California, which can bank power ahead of a spike rather than burning fuel on demand, a gap that gets more expensive to ignore every time a heat wave forces the same choice.
PJM's operators say they haven't actually had to invoke Wright's order yet, and it lapses at midnight Friday regardless. The heat won't. Neither, for that matter, will the data centers, which, as the same dome of high pressure pushes record highs from D.C. to New York, are only getting more of them built along this same stretch of grid.
