Heat Waves Slam the Coasts. Will the Air Conditioners Stay On?

High temperatures from Southern California to the East Coast are putting the nation’s electric grids on alert.

PJM Interconnection, the nation’s largest electricity market which stretches from Chicago to Washington, D.C., issued emergency alerts this week, as it tries to fulfill record demand from people running their air conditioning on full blast even as power plants get stressed by high heat. While there are not yet any imminent fears of rolling blackouts, these warnings from system operators show that electricity supply is getting tight.

The East Coast is expecting quite high temperatures Thursday, with forecasted highs in the upper 90s in Washington, D.C., Newark, and Philadelphia, all major cities in PJM’s market, with high humidity throughout. In New York City, which is part of New York’s electricity market, the National Weather Service issued an excessive heat warning. The NWS has warned that the region — which includes PJM territory in New Jersey — will experience “oppressive heat and humidity” through Saturday.

Get one great climate story in your inbox every day:

On Wednesday night and Thursday morning, PJM instructed generators in its East Coast and Southern regions to “review plans” to see if any maintenance or testing that would take them off the grid could be “deferred/canceled.” It also issued an emergency alert calling for as much electricity generation capacity — i.e. power plants staying online — on the grid as possible.

That alert, known as EEA1, “signals that PJM foresees or is experiencing conditions where all available resources are scheduled to meet firm load, firm transactions, and reserve commitments, and is concerned about sustaining its required Contingency Reserves,” according to its emergency operations manual . In other words, PJM thinks there’s enough generation to meet its expected demand, but is worried about maintaining reserves in case either demand or supply gets out of whack.

High temperatures since June have been challenging the nation’s electric grids, with Texas grid authorities asking for voluntary conservation by consumers in June as they set a new record demand for electricity in generation. During the unrelenting heat wave in Arizona (the forecast high in Phoenix today is 113 degrees, the 28th day in a row temperatures have risen above 110 ), state utilities set new demand records but have not yet had any major reliability concerns. Now there are few places in America where the grid isn't being besieged by heat.

In California, where the inland part of the state especially has been experiencing extreme heat (Bakersfield’s forecast high Thursday is 103), the state’s electric grid has either declared a low level emergency or been put on watch three times in the last week. On Wednesday, the state’s system operator said that “due to some resources going offline, continued excessive heat in interior Southern California, and transmission congestion restricting movement of power to parts of the state where it’s needed,” it had been put on watch for Wednesday evening and had initiated “demand response” programs that encourage energy conservation.

While the California grid has remained stable, the issues it had Wednesday are known concerns when temperatures rise. Hotter conditions can lead to more-than-expected issues with power generation as plants go offline due to mechanical issues and the extreme need for electricity as parts of a power market experience extreme heat can overtax transmission infrastructure.

California is also a global leader in solar power production, which means that the evening hours when the sun goes down but temperatures stay high can be particularly tight. The state has installed a massive amount of energy storage on the grid, however, that can be charged when it’s sunny and electricity is cheap, and discharged in the evening. At 10 p.m. Tuesday night, California's batteries were putting out about 3,500 megawatts, while its entire renewables fleet, which is largely wind at that hour, was producing 5,800 megawatts (meanwhile there was some 25,000 megawatts of natural gas on the grid).

The California Independent System Operator also warned that it was “seeing some supply uncertainty this evening, because of heat potentially pushing up demand, and high electricity demand across the western U.S.”

Heat waves across a broad section of the country are especially concerning for grid operation because they can inhibit imports that some grids need to stay online if an entire region of the country is experiencing high electricity demand.

Globally, this month will likely be the hottest July on record .

Read more about heat waves and electricity:

The Next 2 Years Are Critical for New York City’s Electricity