Why the U.S. grid's extreme heat problem is changing

The increasing frequency of extreme heat is straining the U.S. electrical grid in unexpected ways, beyond simply requiring more electricity to power air conditioners. As climate change causes hotter temperatures to last longer, utilities face a trifecta of challenges during heatwaves: air conditioners, transmission lines, and power plants all become less efficient, while also becoming more fragile and prone to failure.

Michael Webber, a mechanical engineering professor at the University of Texas at Austin, explains that grid operators must contend with less efficient components, increased fragility, and higher demand for electricity.

Hot nights, which typically provide a cooling respite for equipment, are becoming less frequent. In Texas, for example, nighttime temperatures are only dropping to around 78°F instead of the usual cooling to 65°F. This means equipment is operating continuously without adequate downtime to cool down. Rob Gramlich, president of Grid Strategies, emphasizes that local distribution systems, including transformers, need time to cool overnight and may require more redundancy and backup transformers to handle failures.

Prolonged heat can also disrupt the traditional maintenance windows for power plants. A 2024 study co-authored by Webber found that the spring window for lower electricity demand and cooler temperatures in Texas has shifted earlier by 2.4 days per decade, while the fall window has shifted later by 1.1 days per decade. By the mid-2040s, these traditionally milder seasons could merge into a single, extended period of riskier weather, particularly for cold events that could jeopardize grid reliability.

California serves as an example of how solar energy and storage can initially alleviate summer reliability issues, but extended winter cold can pose a greater challenge as electric heating increases demand during low solar output periods.