The end of summer and the transition into fall usually offers the electric grid a chance to catch its collective breath and prepare for the challenges to come in the winter season ahead.
Owners of electricity generators and transmission lines use the milder weather in spring and fall, when electricity demand typically moderates, to shut down temporarily for needed maintenance or upgrades.
PJM has long relied on these “shoulder seasons” to provide a reliable supply of electricity to its 13 states and Washington, D.C., by proactively planning and coordinating equipment outages with its member companies – even with a significant portion of the generation fleet out of service for days or weeks.
But the once-dependable reprieve is not what it used to be. That’s in part because the profile of our customers is changing. Most of the new, rapidly growing energy demand is from data centers and other energy-intensive Large Load customers, and their consumption does not fluctuate significantly with the weather; it is a 12-month 24/7 phenomenon.
That expanding demand is outpacing new transmission and electricity supply coming onto the system.
In addition, unseasonably hot or cold weather now arrives early for summer and winter and stays late.
The result is that periods the grid once relied on for maintenance and preparation can now become periods of significant system stress and reliability risk. Energy flow on the transmission system is increasing while our generation reserves are dwindling, leaving little room for error.
This week has been a prime example. With about more than 61,000 MW of generation outages, PJM was working with only 66% of our generating fleet’s capacity, and the outages were spread across all kinds of resources, from nuclear, coal and gas to wind, solar and hydro.
More than two-thirds of those outages were for planned maintenance or construction, while about 15,000 MW were unplanned outages, according to preliminary data. PJM was able to work with Member companies to recall, or return to service, about 10,000 MW to get to that 61,000 MW number, but canceling more outages would risk those facilities not being able to properly prepare for winter.
On Tuesday and Wednesday, PJM issued a series of emergency procedures to make sure we had enough generation online to serve unseasonably warm, but not extreme, temperatures. The U.S. Department of Energy, for the ninth time this year, issued an order to allow PJM to direct backup generation at data centers and other Large Load electricity customers to operate to avoid outages to other customers. While PJM did not use that authority and has not done so to date, it remains a valuable tool to help protect regular customers.
PJM was able to operate reliably through these challenging conditions this week, as we have throughout the year:
- In April, PJM declared a Hot Weather Alert for its Atlantic coast territory, from New Jersey to North Carolina, when temperatures surged into the 90s.
- In May, a heat wave covered most of the PJM territory for two days and required PJM to summon out-of-service generators and transmission equipment back online.
- And then came September, with two bouts of hot weather just as summer was coming to a close
In the midst of all this, PJM set a new preliminary record for peak electricity use on July 2 at approximately 168,000 MW.
In many of these instances, PJM called on Demand Response to help blunt spikes in electricity demand and ensure transmission security during the hottest days, particularly in the late afternoon and early evening, when solar generation is fading but electricity demand isn’t. PJM has also had to restrict electricity exports to neighboring systems during this time.
Demand Response customers are paid in advance to reduce their electricity use during times of system stress; they provide a valuable service to help control demand on peak days. Previously, Demand Response was called infrequently. In 2026 alone, Demand Response customers, who range from individual homeowners to large industrial plants, have been activated on nine different days, including Oct. 13 and 14. That makes 15 days PJM activated Demand Response between 2025 and 2026, compared with eight days between 2015 and 2024.
PJM and its Members, in coordination with state and federal officials, have relied on these emergency procedures and orders from the U.S. Department of Energy to keep the lights on for all or parts of the grid when PJM’s generation reserves were critically low or transmission constraints were high because of work-related outages.
The DOE issued orders that allowed generators to temporarily run outside of their environmental permit limits in times of emergency and directed data centers to run on their backup generation if directed by PJM to lessen electricity demand.
These tools are important, but they alone may not be enough. Equipment outages will continue to be necessary in shoulder seasons to build multiple, critical transmission projects. Much of the new construction involves upgrading or replacing existing lines to reliably bring energy into areas where generators are retiring and to serve the load that is growing throughout our footprint, because Large Loads are not confined to one area.
Those transmission projects are one part of the puzzle, but building new generation is critical. To this end, PJM has:
- Reformed and streamlined the engineering process for new generation sources to connect with the grid, and we are now pushing to shorten that process even further
- Opened a process to match new Large Load customers with new supply resources
- Received conditional FERC approval for a “Reliability Backstop Procurement” process to secure more generation to fill the supply shortfall in the short term
- Opened an accelerated process to connect large, state-sponsored projects that can provide reliable supply as soon as possible
PJM has also sharpened our forecasting process so that we understand just how much proposed Large Load demand is likely to materialize and when, in addition to the approximately 11,000 MW of data center load already on the system.
While this work is continuing, you may notice the extra activity and emergency procedures happening to balance our system in this new reality, until the necessary generation and transmission can be placed in-service, which is not expected to occur in the immediate future.
As you can see, PJM is taking action on many fronts, in collaboration with our partners in industry and state and federal government, to preserve the reliable electric service that the region has enjoyed for decades.