(Bloomberg) — Back-to-back heat waves across the US are straining electricity grids serving millions of households and businesses amid a surge in demand from data centers that require around-the-clock power.

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Call it a new normal for the US power system: Seasonal weather extremes overlap with the growing electricity needs of factories and the artificial intelligence sector. As households crank up air conditioners to cope with temperatures topping 100F (38C), power reserves shrink and decades-old transmission equipment is stressed.

The challenges facing regional transmission operators, or RTOs, that manage grids serving more than 150 million Americans are multiplying. And it’s not at all certain that RTOs that were created and shaped during a long period of somnolent demand growth are up to the task.

“There are expressed concerns from RTOs that we are reaching tipping points,” said Timothy Fox, an analyst at ClearView Energy Partners LLC.

Emergency alerts have been cascading across grids covering more than half of the 50 US states in recent weeks, including the Midcontinent Independent System Operator (MISO), and the Southwest Power Pool, which manage electricity systems from the Midwest to the Rocky Mountains.

But perhaps the greatest strain has centered on PJM Interconnection LLC, which serves 67 million people from Chicago to Washington, DC. Searing heat earlier this month boosted power demand across a territory that includes Virginia’s Data Center Alley, one of the biggest concentrations of AI facilities.

Another heat wave already is building across the western and central US, according to the US Climate Prediction Center, with temperatures forecast to hit 105F in coming days in Texas and elsewhere.

PJM has long prided itself on maintaining reliability but it’s being tested after a long stretch of stagnant power demand. Usage soared to an unprecedented 168 gigawatts on July 2, topping the high that had stood for two decades as triple-digit temperatures gripped the nation’s capital and spread across the Mid-Atlantic.

While the heat was intense, “it’s certainly not out of the ordinary to see these types of temperatures, especially in places like eastern PJM,” said Ed Vallee, a meteorologist at Atmospheric G2. Washington often tops 100F at least once a summer, he added.

“One of the more interesting takeaways from this summer is that many of the reliability concerns and demand records have occurred during weather that has been notably warm, but generally not historically extreme,” said Bradley Harvey, lead forecaster at Vaisala Xweather.

What has changed is humidity that makes high temperatures feel more oppressive, Vallee said. As the planet warms due to climate change, the air can hold more moisture, which inhibits overnight cooling and extends power demand later into the evening.

PJM issued two rounds of emergency alerts this month and sought permission from the US Energy Department for data centers to deploy backup generators. The Southwest Power Pool also secured federal permission to max out generation after issuing its highest level of alerts for parts of Wyoming, Colorado, Utah, Arizona, Montana, New Mexico and Nebraska.

As for PJM, the flurry of alerts suggests deep issues with stability, Peter Lake, the outgoing senior director of power at the White House’s National Energy Dominance Council, said at a July 23 conference. “That’s certainly not a grid poised for growth.”

PJM didn’t reply to a request for comment.

To be sure, not all grids are seeing the same level of strain. Texas, which experienced massive blackouts during a deadly winter freeze in 2021, has added enormous amounts of renewable generation to its largest grid. By the end of the year, the Electric Reliability Council of Texas estimates more than 114 gigawatts of solar, wind and battery storage systems will be connected to the system.

Ercot also set new demand records this month amid searing temperatures and humidity, according to preliminary data. Even so, the grid operator hasn’t declared an energy emergency in almost two years, said Trudi Webster, an Ercot spokeswoman.

Ercot “continues a reliability-first approach to grid operations and will continue to operate the grid conservatively, bringing generating resources online early to mitigate sudden changes in generation or demand,” she said.

Demand for electricity is expected to nearly double over the next decade, said Shawna Berger, the communications director for SPP. “SPP is working with utilities, regulators and others to keep energy reliable and provide value to its members as it has for more than 80 years,” she said.

MISO said that new generation capabilities are coming online as it works to maintain a reliable grid.

“MISO’s system has operated through some of the most extreme weather and highest demand conditions on record, and we remain focused on ensuring we can continue delivering reliable service for the 45 million people in our region,” McKenzie Barbknecht, a MISO spokesperson said in an email.

But for grids that have grown brittle, there isn’t a quick or cheap fix. After a decade of low investment, New York’s system is increasingly vulnerable to blackouts, according to Gary Cunningham, director of market research for Tradition Energy.

“Maintaining reliability through this transition depends not only on the quantity of resources connected to the system, but on whether the evolving resource mix can provide the operational capabilities required under real‑world conditions,” Kevin Lanahan, a spokesman for the New York Independent System Operator, said in an email.

The situation at PJM in particular is projected to get worse in coming years, experts said. The grid recently held a series of so-called capacity auctions to secure enough power to meet periods of high demand. They have come up short and concerns are mounting that PJM won’t have enough resources to navigate a major winter storm, like the one that sent temperatures plunging across the US East in January, Lake said.

The grid is pushing ahead with plans to shore up its system: PJM is set to hold an emergency auction after the summer in order to make sure data centers pay for the generation they require. But getting it up and running will take time.

“You have more power needs than ever and fewer generation and transmission resources to deliver it,” Cunningham said. “It’ll take years and billions, if not trillions of dollars in investment. That’s just the sad truth.”

–With assistance from Brian K. Sullivan and Naureen S. Malik.

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