PJM Interconnection, the grid operator for 13 states and the District of Columbia, set a preliminary all-time peak load of about 168,158 megawatts between 5 and 6 p.m. on July 2, 2026, according to a PJM update published on July 10. The previous record, 165,563 MW, was set on August 2, 2006. The new figure includes an estimate of demand that was suppressed by demand response programs, reflecting the load the system would have had to serve without those curtailments.
The PJM region recorded its hottest-ever average air temperature across its footprint, 97 degrees, on July 2, with many areas in the Mid-Atlantic in the low 100s. PJM said the day also set a record for average combined heat and humidity.
Tight conditions
"This was the highest peak we have ever served, through an unprecedented heat wave," Paul Dajewski, PJM's senior manager of dispatch, told the Operating Committee on July 9. He said PJM used every available generator on July 2.
Forced generation outages ranged between 18,100 MW and 19,400 MW from July 2 to 4, well above the 12,800 MW average outage level on the top 10 summer peak days of the previous three years. As load approached its peak around 5 p.m., some generators tripped offline, and PJM executed emergency procedures to maximize supply and manage demand.
The record load approached PJM's 90/10 seasonal forecast of 169,128 MW, a level with a 1-in-10 chance of occurring that is built into summer planning. Dajewski said the system's performance did not change the fact that conditions are growing tighter as new supply fails to keep pace with demand. "Our capacity position continues to be an area of concern," he said.
Demand response and emergency orders
PJM called on emergency demand response, under which customers are paid in advance to reduce use during emergencies. Preliminary estimates put demand response performance at about 6,113 MW on July 2 and 5,037 MW on July 3. Official performance evaluation takes 60 days, so final peak figures will not be posted before then.
PJM requested and received an emergency order from the US Department of Energy under Section 202(c) of the Federal Power Act, providing temporary relief from environmental permit limits for generating units. PJM estimated about 3.25 GW of generation ran beyond permit limits under that order.
A second 202(c) order authorized PJM to direct transmission owners, as a last resort to avoid outages for residential and other customers, to curtail data centers and other large loads equipped with backup generation. On the evening of July 2, PJM issued an Emergency Use of Backup Generator Warning for the BGE, PEPCO and Dominion transmission zones, notifying large load customers to be ready to switch to backup generation within 15 minutes. The follow-up action was not needed. Both orders were effective from July 1 through July 6.
Data centers in the balance
The Dominion zone in northern Virginia hosts the world's largest concentration of data centers. Data center growth is the main driver of PJM's rising load forecasts, and it has been central to debates over capacity prices, which reached record levels in recent auctions. The use of an emergency order to allow curtailment of large loads with backup generation is a new step in how grid operators manage data centers during emergencies.
PJM has been developing rules for integrating large loads, including proposals that would require new large loads to bring their own generation or accept curtailment during emergencies. The July event provides a real-world test of how data centers respond when called upon. Many data centers have diesel backup generators sized to carry their full load, but running them for extended periods raises air permit questions, which is one reason DOE emergency authority was involved.
Heat and the grid
Extreme heat strains grids in several ways. It drives up air conditioning load, reduces the efficiency of gas turbines and thermal plants, lowers the capacity of transmission lines and can cause equipment failures. The high forced outage rate during the July heat illustrates the last of these. Solar output is typically strong during summer afternoons, but demand often stays high into the early evening as solar output falls, which is when PJM's peak occurred.
Climate data show that heat waves in the eastern United States have become more frequent and intense. PJM and other grid operators have begun incorporating hotter weather scenarios into their planning. The 90/10 forecast itself is based on historical weather patterns, and the near-match on July 2 shows how close actual conditions came to the planning extreme.
Neighbors and imports
PJM said generation and transmission owners and neighboring grid operators coordinated closely during the event. Imports from neighboring systems can help during regional peaks, but a heat wave covering much of the eastern United States limits how much spare power neighbors have to offer. The Midcontinent ISO, New York ISO and ISO New England faced high demand during the same period. Interregional transmission capacity, which has grown slowly, sets an upper bound on how much help can flow between systems during such events.
Market effects
Real-time power prices in PJM spiked during the heat, as is typical when reserves run thin. The event will feed into debates about capacity market design, resource adequacy and the pace of new generation. PJM's capacity auctions have cleared at the price cap in recent years, and the grid operator has warned of potential shortfalls later in the decade as retirements of older plants coincide with rapid load growth.
The use of environmental waivers to run plants beyond permit limits also raises regulatory questions. DOE has used 202(c) orders more frequently in recent years, including to keep some fossil plants scheduled for retirement in operation. Environmental groups and some states have challenged those orders, while grid operators have defended them as necessary for reliability.
What to watch
Key items include PJM's final peak figures after demand response evaluation, the outcome of large-load integration proposals, the next capacity auction and whether further heat waves this summer bring the system back to emergency conditions. Regulators and data center operators will also be assessing how the backup generator warning worked in practice.