Report: Heat wave results in highest U.S. electricity demand since 2017

From July 15 through July 22, 2019, a heat wave extending from the Midwest to the Atlantic coast brought extremely high temperatures and humidity to those regions. The high temperatures resulted in elevated demand for electricity to power air conditioners, dehumidifiers, fans, and other cooling equipment. In the hour ending at 6:00 p.m. ET on Friday, July 19, hourly electricity demand in the Lower 48 states peaked at 704 gigawatts (GW), according to data from the U.S. Energy Information Administration’s (EIA) U.S. Electric System Operating Data. Electricity demand has not been this high since July 20, 2017, nearly two years ago, when electricity demand in the Lower 48 states hit 718 GW.

Demand for electricity was relatively high throughout each day of the heat wave. Typically, electricity demand in the summer is highest midday or in the late afternoon and lowest in the middle of the night. On a typical summer night, electricity demand for the Lower 48 states is usually lower than 400 GW, but during the heat wave, nighttime electricity demand remained between 430 GW and 450 GW. For this reason, more power generating plants operated continually during the heat wave.

Although demand for power was relatively high nationwide 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 2019.

Similarly, peak power demand in the Electric Reliability Council of Texas (ERCOT) region during the heat wave reached 70,177 MW on the evening of July 16, which was lower than ERCOT’s summer peak forecast of 74,853 MW, issued in early May 2019.