WASHINGTON, D.C. – The U.S. Department of Energy is pointing to grid performance during a record-breaking heat wave earlier this month as evidence of the importance of maintaining conventional power generation, citing steep declines in wind and solar output during periods of highest electricity demand.
In a statement, the department said customers served by the PJM Interconnection experienced extreme electricity demand on July 2 and 3, when temperatures averaged about 97 degrees across much of the region. PJM, the nation’s largest regional transmission organization, reported a preliminary all-time peak demand of approximately 168 gigawatts during the event.
DOE cites renewable output during evening peak
According to the department, during the 5 p.m. peak demand period on both days, about 82% of available wind generation was unavailable. By sunset, the department said, approximately 99% of solar generation had gone offline as daylight faded.
“Thankfully, we have stopped the premature shutdown of reliable power,” the Department of Energy wrote in its post.
The department used the figures to argue that dispatchable energy sources—including natural gas, coal and nuclear power—remain essential to maintaining grid reliability during periods of extreme demand.
Grid operators faced multiple challenges
PJM’s operational reports also showed that the heat wave affected more than renewable resources. Extreme temperatures contributed to forced outages at several conventional generating units, temporarily reducing available capacity from fossil fuel and other dispatchable power plants.
New Jersey Governor Mikie Sherrill is starting to realize this reality. Earlier this month, she signed a new law that attempts to reverse decades of power plant shutdowns in her state.
This came after residents of New Jersey, once a regional power supplier has become dependent on other states for its power needs, and prices spiked higher than any other state in America.
Sherrill signed the bipartisan “Power NJ Act” on July 13, launching a competitive state framework to procure at least 1,100 MW of new advanced nuclear generation.
Energy experts note that solar generation declining near sunset is an expected characteristic of the technology rather than an equipment failure, unlike coal, natural gas, and nuclear power which isn’t affected by daily sunrises and sunsets.
Grid operators routinely plan for that daily transition by relying on a mix of generation sources, energy storage, imports and demand management to balance supply and demand. In New Jersey, those options are limited after multiple power plants have gone dark in the past 10 years. The state had to rely on the PJM network to fulfill its basic energy needs during the heatwave, leading to higher costs for residents when they needed the energy to run air conditioners, refrigerators and critical medical equipment.
Why it matters
The performance of the electric grid during extreme weather has become a central issue in national energy policy. Supporters of expanding conventional generation argue recent demand records demonstrate the need for reliable, dispatchable power, while advocates of renewable energy point to investments in battery storage, transmission upgrades and diversified generation portfolios as key to improving grid resilience.
The Department of Energy’s statement reflects the administration’s position favoring the continued operation of conventional power plants alongside ongoing discussions about the nation’s evolving energy mix.
PJM has not characterized the decline in solar output at sunset as a system failure, but rather as part of the normal operating conditions grid operators plan for each day, recognizing the shortfall.
