Under extreme heat, electricity demand on the largest U.S. power grid hits a record.

The continuing heatwave in the eastern United States is pushing the nation’s largest power grid to its limits. Electricity demand at the PJM Interconnection grid on July 2 is likely to break the historical record set in August 2006; meanwhile, the risk of power outages is rising, electricity prices are soaring, and the grid’s vulnerability is once again drawing widespread attention.

On July 4, Bloomberg reported that PJM Interconnection LLC covers 13 states from Washington D.C. to Chicago, serving 67 million people. The grid stated that demand on July 2 is likely to surpass the previous historic peak of 165.563 gigawatts. The Department of Energy has ordered all generator units to operate at maximum capacity, including backup power sources—this is the second time this emergency measure has been activated this summer.

The impact of the high temperatures has reached daily life and the markets. New York City’s power company Consolidated Edison cut off electricity to nearly 10,000 customers in southwest Queens due to equipment failure and asked tens of thousands of customers to proactively save electricity. In some areas, PJM electricity prices surged this week to more than $2,500 per megawatt hour. Over 197 million people are under extreme heat warnings or advisories, covering areas from Kansas to Maine.

PJM grid under pressure, demand approaches maximum capacity

The PJM grid issued a series of emergency alerts this week. If demand on July 2 is officially confirmed to break records, it means the grid’s operating load will exceed 90% of its capacity. However, as temperatures climb, some generating capacity has already shown a deficit—about 9.5 gigawatts of generator units in the mid-Atlantic region are offline, including those concentrated in northern Virginia’s data centers. One gigawatt is equivalent to the installed capacity of a traditional nuclear power station.

Notably, PJM previously stated that setting a demand record this summer was “unlikely, but not impossible.” Final official data must go through 60 days of demand response resource calculations before confirmation. Thursday’s data showed instantaneous load between 5 p.m. and 6 p.m. was about 162.7 gigawatts, but this figure had already been somewhat suppressed.

On Friday, as holiday travel led to a slight drop in electricity use, overall consumption was expected to ease slightly, but continued high temperatures and humidity were likely to drive cooling demand back up. Continuous operation under high loads will further increase the risk of equipment and critical infrastructure failures.

Reports indicate that a strong heatwave has persisted in the eastern United States this week, bringing triple-digit Fahrenheit temperatures to several cities. On Friday afternoon, temperatures in Central Park, New York City reached 98°F (36.7°C), and on Thursday the city hit 100°F, setting the highest record since 2012. Weather forecasts show that the hot and humid weather is expected to continue throughout the weekend, covering the eastern half of the U.S.

High temperatures have also directly affected Independence Day celebrations. The “Great American State Fair”—a two-week patriotic-themed festival held at Washington’s National Mall—was forced to close for several hours on Friday due to high temperatures; organizers announced via social media that the event would resume in the evening.

Frank Pereira, senior forecaster at the U.S. Weather Prediction Center, said, “Today’s weather will be extremely tough,” noting that temperatures are “well above normal levels” from the Plains, Midwest, mid-Atlantic, to the Northeast.

Data center expansion and extreme weather heighten structural pressure on the grid

This heat crisis is not an isolated event but reflects the deep structural pressures facing the U.S. power grid. Even before this wave of high temperatures, U.S. grids have been under sustained pressure due to a boom in data center construction—this wave of expansion has broken two decades of stagnant electricity demand. Northern Virginia, where the PJM grid is located, is the core area of America’s “data center corridor.”

Extreme temperature fluctuations make the grid more prone to failure during peak periods, with impacts ranging from residential air conditioner use to critical scenarios like hospital lighting and power supply. Besides cutting off power to some users, Consolidated Edison has also asked customers to reduce the use of washing machines, dryers, and microwaves, and to use only one air conditioner if they have two.

Former U.S. Department of Energy official Jigar Shah said: “We need to view grid flexibility as part of daily operations—not just a crisis response tool.” Analysts believe this high-temperature stress test will further increase calls for grid reform, promoting additional generating capacity and enhancing system flexibility.

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