US Power Grids Smash Summer Demand Records as Heat Drives Cooling Load

Three of the largest regional grid operators in the United States closed out the summer with new all-time highs for hourly electricity demand, according to data submitted on Form EIA-930 and tracked through the Hourly Electric Grid Monitor.

PJM, which coordinates the grid across parts of the Mid-Atlantic and Midwest, hit 162.6 gigawatts on July 2, 2026. That tops its previous high of 160.6 GW, set on June 23, 2025, by 1.3%. The Electric Reliability Council of Texas pushed further ahead, reaching 91.1 GW on July 22, 2026 — a 6.5% jump over its prior record of 85.5 GW from August 20, 2024. The Southwest Power Pool logged 58.0 GW on July 27, 2026, beating its earlier peak of 56.0 GW recorded on August 21, 2023 by 3.5%.

The timing of these records lines up with a straightforward explanation: most landed during regional heat waves, and the summer as a whole was the hottest on record nationwide. As temperatures climbed, so did air conditioning use, pulling the grid toward its limits.

The story was more mixed for the remaining independent system operators, several of which came close to — but did not break — their own records. CAISO in California reached 50.0 GW on September 9, 2026, staying below its 51.1 GW high from September 6, 2022. ISO-NE topped out at 25.3 GW on July 2, 2026, short of the 25.9 GW mark it set on June 24, 2025. NYISO recorded 31.1 GW on July 2, 2026, under its previous 31.9 GW peak from June 24, 2025, though the operator notes a higher 34.0 GW figure from 2013 that predates the hourly data collection used here. MISO saw 121.5 GW on June 30, 2026 — the highest in the Hourly Electric Grid Monitor’s dataset, but still below the 127.1 GW peak MISO itself reported on July 20, 2011.

These figures come from Form EIA-930, which balancing authorities submit and which is published as-is. The values represent the best data available at the time of reporting, and reporting quirks can affect quality, so numbers issued directly by the balancing authorities may not always match. Even so, the pattern is clear: a hotter climate is translating into heavier summertime strain on the country’s transmission networks, a dynamic that will shape planning decisions around generation capacity, reliability, and grid upgrades in the years ahead.