U.S. DOE Says 99% of Solar Was Unavailable After Sunset

U.S. Department of Energy Claims 99% of Solar Capacity Failed After Sunset While 82% of Mid-Atlantic Wind Failed During Peak Demand

The U.S. Department of Energy (DOE) issued emergency orders to help protect the nation’s largest power grid during an intense early July heat wave. The orders allowed PJM Interconnection to dispatch additional generating units and use backup generation resources as electricity demand surged across the Mid-Atlantic.

PJM forecast peak electricity demand of about 162,860 megawatts on July 2, close to its all-time record. The grid operator warned that extreme temperatures above 95°F across much of its service area could threaten reliable electricity supplies without emergency action.

According to the DOE, renewable generation was limited during the evening peak. Wind generated about 2,152 MW from 11,728 MW of installed capacity at around 5 p.m. Solar output dropped to just 138 MW from 18,524 MW of installed capacity after sunset. The department said this meant about 82% of wind capacity and 99% of solar capacity were unavailable during the critical demand period.

Customers of the largest U.S. regional power operator, PJM, experienced a heat wave on July 2-3 that triggered peak electricity demand. During the 5pm peak demand hours on both days, 82% of available wind power failed. By sunset, despite still high temps, 99% of solar power also… pic.twitter.com/Rd0sPM4BNS

— U.S. Department of Energy (@ENERGY) July 23, 2026

The emergency order authorized PJM to operate additional generating units, including resources that normally face environmental or operating restrictions during emergencies. Backup generators at data centers and other large facilities were also made available to reduce pressure on the grid and lower the risk of blackouts.

On July 2, PJM issued emergency alerts and ordered all available generating resources to operate. Grid reserves dropped sharply during the evening as air-conditioning demand climbed. Wholesale electricity prices briefly surged as operators worked to maintain system reliability.

Despite the extreme conditions, PJM avoided widespread outages. Demand-response programs and emergency operating measures helped keep peak demand below the grid’s all-time record of 165,563 MW, which was set in 2006. Electricity demand eased as temperatures moderated after the holiday weekend.

The event highlights the growing challenge of maintaining grid reliability during extreme weather. Rising electricity demand from air conditioning, data centers, and electrification is increasing pressure on power systems. Grid operators are relying on a broader mix of generation, storage, demand response, and emergency measures to keep electricity flowing during peak demand periods.

Source:

• U.S. Department of Energy (DOE) on X