This summer, the United States hit the second highest peak electricity demand since the Energy Information Administration began collecting data in 2016, the agency said.
Peak hourly electricity demand in the continental United States reached 741,815 megawatt hours on July 27, 2023, just under the all-time high of 742,704 MWh recorded on July 20, 2022, the EIA said.
Peak hourly electricity demand typically occurs in July or August when cooling demand is highest and is usually weather driven, but it can mask regional grid strains because the continental U.S. electric grid operates as three separate, nearly unconnected, electric systems – Eastern, Western, and Texas, the EIA said. Those systems can be affected by individual weather patterns or resource availability that create differences in the timing and intensity of when demand is the highest.
For example, the EIA noted that last summer hot weather was concentrated in Texas and the western United States -- the electric systems in those areas of the country strained to meet higher demand.
The EIA also noted that the Electric Reliability Council of Texas broke all-time peak hourly demand records as extreme heat settled in the region for most of July and August, leading to hourly wholesale electricity prices in excess of $4,000/MWh and to ERCOT issuing appeals for consumer electricity conservation for several days in August.
And high temperatures continued in September, combined with lower wind and solar output in the evening, leading ERCOT to declare an Energy Emergency Alert Stage 2 on September 6. An EEA Stage 2 is the last step before a grid operator is forced to enter rotating outages to ensure grid stability.
In the Western Interconnection, widespread heat in late July caused the California Independent System Operator to call an Energy Emergency Alert Stage 1 on July 20. CAISO, unlike ERCOT, relies heavily on imported electricity from neighboring regions. However, widespread heat can limit the ability of neighboring systems to share resources when capacity is needed to meet load within their own systems, the EIA noted.
Even though forecasts for high temperatures on July 20 across the Western Interconnection elevated demand in California, the Southwest, and the Northwest, sufficient resources were available to meet demand within California that day without the need to declare additional staged emergencies or shedding load.
In the Western Interconnection, the actual peak hour of the year occurred on August 17, when demand across the three regions reached 137,370 MWh, but grid operators were able to meet demand without entering into emergency conditions, the EIA said.
In the Eastern Interconnection, hourly demand peaked on July 27, at 529,147 MWh, the same day that demand peaked for the continental United States, the EIA said, adding that peak demand was also high for a few days in August when hot weather moved through the Central United States and into the East Coast.
The PJM Interconnection and the Midcontinent Independent System Operator, the two largest system operators in the Eastern Interconnection, declared hot weather alerts in August but did not need to enter emergency conditions. High temperatures in early September also increased peak demand in New York and New England, but system operators there did not need to enter emergency conditions.