By: Kevin Randolph |

The recent heat wave that occurred from July 15 through July 22 and extended from the Midwest to the Atlantic coast resulted in the highest electricity demand in the United States since 2017, according to the U.S. Energy Information Administration (EIA).

In the hour ending at 6:00 p.m. ET on July 19, hourly electricity demand in the Lower 48 states peaked at 704 gigawatts (GW), according to the EIA’s U.S. Electric System Operating Data.

That peak was the highest electricity demand since July 20, 2017, when electricity demand in the Lower 48 states reached 718 GW.

On a summer night, electricity demand in the Lower 48 states is typically lower than 400 GW. During the heat wave, nighttime electricity demand remained between 430 GW and 450 GW, causing more power generating plants to operate continually.

EIA noted that although demand for power was relatively high across the country during the heat wave, actual demand generally stayed within expectations of regional grid systems.

In New England, hourly power demand peaked at 23,865 megawatts (MW) at the hour ending at 7:00 p.m. ET on Saturday, July 20. This level was lower than the New England Independent System Operator’s summer peak forecast of 25,323 MW, based on summer forecasts it made in May

Peak power demand in the Electric Reliability Council of Texas (ERCOT) region hit 70,177 MW on the evening of July 16, which was lower than ERCOT’s summer peak forecast of 74,853 MW.

However, in the PJM Interconnection, peak power demand was higher than the summer peak forecast.

Hourly power demand peaked at 152,315 MW at 6:00 p.m. CT on Friday, July 19. In May, PJM issued a summer peak forecast of 151,000 MW. In that hour of peak demand, generators in PJM dispatched 155,263 MW of power and supplied more than 3,000 MW to adjacent grids.

During the heat wave, daily electricity demand in the Lower 48 states was the highest it has been this year, reaching a high of more than 14,000 gigawatt-hours on July 19, the highest daily value in almost two years, according to EIA.

By July 23, when temperatures had subsided, demand for electricity also fell. Demand for electricity on that day in the Lower 48 states peaked at 589 GW.