By - Jim Vess

July heat wave drove peak electricity demand to two-year high in the East and Midwest

Energize Weekly, August 7, 2019

Electricity demand during the July heat wave that covered the Midwest and Atlantic coast led to the highest electricity peak – 704 gigawatts (GW) – in two years, according to the federal Energy Information Administration (EIA).

The heat wave, which also brought high humidity, extended from July 15 to July 22, and the peak demand was hit on July 19 at 6 p.m. Eastern time. That is the highest it has been since July 20, 2017, when electricity demand peaked at 718 GW for the Lower 48 states.

The high demand came primarily from air conditioning, dehumidifiers, fans and other cooling equipment, EIA said.

“Demand for electricity was relatively high throughout each day of the heat wave,” the agency said. “Typically, electricity demand in the summer is highest midday or in the late afternoon and lowest in the middle of the night.”

The typical demand on a summer night for the Lower 48 states is less than 400 GW, while it can rise to between 430 GW and 450 GW for nighttime demand during most heat waves.

While electricity demand was high nationwide, it varied regionally. In New England, demand peaked at 23,865 megawatts (MW) on July 20 at 7 p.m. That was lower than ISO New England had forecasted for this summer’s peak – a 25,323 MW peak.

In Texas, the peak – 70,177 MW – came on the evening of July 16. It was lower than the Electric Reliability Council of Texas (ERCOT) summer peak forecast of 74,853 MW issued in May.

There was, however, a higher peak than expected for PJM Interconnection, the grid manager covering utilities in the mid-Atlantic region and some Midwestern states, extending as far as the Chicago area.

PJM had forecast a summer peak of 151,000 MW, but on July 19 at 6 p.m., system demand peaked at 152,315 MW. In that hour, PJM dispatched 155,263 MW, supplying more than 3,000 adjacent grids.

Temperatures dropped on July 23, and so did electricity demand with the peak that day at 589 GW, “a level more consistent with hourly peak values of a typical summer day,” EIA said.

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