The US power grid is facing another major test. After a massive heat dome settled over the US last week, temperatures pushed into the triple digits across major cities from St. Louis to Boston. In several places, especially in the Southeast and Midwest, high humidity, compounded with extreme heat, is making conditions feel even worse. Once rare, these kinds of extreme humid heat events are now routine, driving electricity demand to historic highs that test the grid just when people need cooling the most.
On June 24, the PJM Interconnection — serving 65 million people across 13 states — hit nearly 161 GW of peak demand, its highest since 2011. That spike, fueled by air conditioner (AC) use amid extreme heat and humidity, came dangerously close to exceeding system capacity. And it’s not just PJM. From Texas to North Carolina, utilities are issuing conservation warnings, and localized outages are becoming more common.
AC keeps homes livable, protects food and medicine, and cools essential infrastructure like data centers and hospitals. But the power systems we rely on weren’t built for this kind of sustained, widespread demand. As heat waves intensify, our growing dependence on cooling systems is straining the grid like never before.
The cooling dilemma
In the United States, ACs are nearly universal — installed in about 90 percent of homes — and their electricity draw is obvious come billing time. In parts of California, ACs can account for 60 percent of peak summer demand in residential buildings. As warming accelerates alongside increased urbanization and population growth, the AC stock in the US is expected to grow to 542 million units by 2050, a 35 percent increase from 2020, putting even more intense pressure on our power systems.
Yet today’s ACs aren’t designed to meet this challenge. The most common units in use are also among the least energy efficient options on the market, often use refrigerants with high global warming potential, and are not optimally designed to tackle a crucial comfort component: humidity. If we continue to rely on current technologies, we risk overwhelming power systems, driving up emissions, and leaving vulnerable communities even more at risk by making air conditioning financially unviable to own and operate.
That’s why we need smarter, more energy-efficient, and more affordable ways to keep cool. Primarily, solutions that can respond to real-world conditions, real-time cooling needs — and help stabilize the power grid.
Excerpted from Rocky Mountain Institute July 31, 2025. Authors: Ian McGavisk, Lauren Shwisberg, and Ankit Kalanki
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Super-efficient ACs to the rescue
One solution is rethinking ACs themselves.
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Thinking outside the window box: cooling innovation
Startups are also advancing a broader wave of cooling innovation
What’s next?
We shouldn’t have to choose between comfort and security
