Three U.S. grid operators carried more load this summer than ever before. In a note published on 15 October, the U.S. Energy Information Administration (EIA) reports new hourly peaks for PJM, ERCOT and the Southwest Power Pool, based on the Form EIA-930 data the balancing authorities file. Most of the peaks came during regional heat waves in what EIA calls the hottest summer on record for the country as a whole, with air conditioning pushing demand up.
The Numbers
- PJM: 162.6 GW on 2 July 2026, 1.3 % above the 160.6 GW of 23 June 2025.
- ERCOT: 91.1 GW on 22 July 2026, 6.5 % above the earlier record of 85.5 GW, which EIA dates to 20 August 2024.
- SPP: 58.0 GW on 27 July 2026, 3.5 % above 56.0 GW on 21 August 2023.
The other regions came close without breaking their marks. CAISO reached 50.0 GW on 9 September against a record of 51.1 GW from 2022. ISO-NE peaked at 25.3 GW and NYISO at 31.1 GW, both on 2 July and both short of their June 2025 highs. MISO's 121.5 GW on 30 June is the highest value in EIA's hourly grid monitor, but MISO itself reports 127.1 GW from July 2011, before EIA collected hourly data. EIA adds that the EIA-930 figures are published as reported and can differ from what the operators publish themselves.
ERCOT's Jump Is The One To Watch
PJM and SPP moved their records by a few percent. ERCOT added 5.6 GW in one step. The EIA note does not split the peak into weather and new load, and it does not mention data centers at all, so the share of the jump that comes from new campuses is not in the data. Earlier this month EIA forecast record U.S. power demand for 2026 and 2027, with data centers named as a driver (our report).
For anyone running standby or on-site plant, the calendar matters as much as the gigawatts. The grid is tightest on the same afternoons when outdoor air is hottest. That is when a utility may ask large customers to start their own generators, and when those engines, their alternators and their cooling equipment see the worst ambient of the year. A load test in April does not show how a data center generator yard behaves on a July afternoon after several hot days in a row.
One practical point for project teams: the design ambient in a specification is often taken from an older climate table. After a summer like this one it is worth checking it against the station data of the last few years.
Sources: U.S. Energy Information Administration, Microgrid Media
