In-brief analysis
June 27, 2025
Electricity demand in the PJM Interconnection and ISO New England (two regional grid operators covering the Northeast United States) reached multiyear highs on June 23 and June 24, respectively. Electricity demand increased significantly due to a heat wave that affected most of the Eastern United States this week.
PJM Interconnection
Electricity load in the PJM Interconnection, the largest wholesale electricity market in the country, peaked at 160,560 megawatts (MW) on Monday, June 23, between 5:00 p.m. and 6:00 p.m. according to data from our Hourly Electric Grid Monitor. The load on the grid surpassed PJM’s seasonal peak load forecast of 154,000 MW but remained below the record load of 165,563 MW in 2006 (PJM has expanded numerous times, and this data point is based on PJM’s current footprint). PJM’s footprint includes 13 states and the District of Columbia.
Real-time wholesale electricity prices on June 23 peaked at $1,334 per megawatthour (MWh) at 7:00 p.m. according to PJM, compared with peak prices of $52/MWh on June 16.
At peak load on June 23, 44% of PJM’s generation came from natural gas, 20% from nuclear, 19% from coal, and 6% from solar. The remaining generation came from a mix of hydro, wind, petroleum, and other generation. Petroleum generation, which is generally the most expensive form and therefore only used to meet large demand loads, was three times greater compared with the same hour the day prior.
ISO-New England (ISO-NE)
As the hot weather moved eastward, demand peaked the following day in ISO-NE—the integrated grid operating in Maine, Vermont, New Hampshire, Massachusetts, Rhode Island, and Connecticut. Peak demand on Tuesday, June 24, between the hours of 6:00 p.m. and 7:00 p.m. eastern time was 25,898 MW, according to the data in our Hourly Electric Grid Monitor. ISO-NE reported that Tuesday’s evening peak electricity demand was the highest level seen in the region since 2013.
Real-time wholesale electricity prices on June 24 peaked at $1,110/MWh at 6:00 p.m. according to preliminary data from ISO-NE, compared with peak prices of $65/MWh the previous week on June 17.
New England’s electricity grid depended on a combination of oil-fired power plants, electricity imports from Canada, and increased natural gas power production to meet peak demand this week. At peak load on Tuesday, 47% of ISO-NE generation came from natural gas, 12% from imports, 13% from nuclear, 12% from petroleum, 1% from coal, and 4% from renewable sources including wind, batteries, and solar. The last remaining coal-fired plant in the region, the Merrimack facility in New Hampshire, supplied 280 MWh on average to the grid on Tuesday. The Merrimack facility is typically only used when demand is high.
Principal contributors: Lindsay Aramayo, Kimberly Peterson