When a massive heat dome settled over the U.S. in late June and early July, it wasn't just people feeling the strain. The nation's power grid was pushed to the edge, too.

At the peak of the event, about 160 million people across 30 states were under extreme heat alerts. Electricity demand surged so high that the U.S. Department of Energy declared an energy emergency, while PJM Interconnection (the grid operator serving most of the affected states) topped a record for energy demand that had stood since 2006.

Why does hot weather stress the power grid?

According to Amy Myers Jaffe, director of the Global Energy, Climate, and Sustainability Lab at New York University, all of the electricity needed to power our daily lives is starting to add up.

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Between air conditioners, electronic devices, data centers, manufacturing and vehicles, we're "stretching the grid past its actual capacity to provide the supply to equal the demand," she said.

And the heat itself makes the infrastructure less efficient.

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"Our grid and the equipment is metal, which heats up when it's hot," Jaffe explained. "All of these things compound each other."

Your risk depends on where you live

Not every power grid is built the same. Jaffe points to PJM. which serves states stretching from New Jersey through Pennsylvania and much of the Mid-Atlantic and Midwest, as one area facing particular challenges.

"They have not modernized how they manage adding new generation capacity and how they manage surges in demand," she said.

Meanwhile, some states that have historically dealt with major grid issues have started to become more resilient.

"In Florida, Texas and California," she explained, "There've been a tremendous improvement in how many batteries have been installed."

Whether they're connected to large solar farms or installed in homes, batteries are increasingly helping utilities shift electricity from times of low demand to the hottest hours of the day.

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Warning signs your local grid may be vulnerable

Jaffe says there are clues that can reveal how resilient your system is:

• If transformers or neighborhood equipment regularly fail
• How quickly your utility restores power after storms
• Whether aging equipment is being replaced
• New charges or surcharges appearing on your electric bill

Prepare for the next heat wave

Jaffe suggests three small steps to help reduce stress on the grid, and on your wallet, before temperatures spike again. 

1. Find out if the utility that runs your area is utilizing the benefit of batteries and enroll your home in any battery-powered programs.
2. Check for any deals offered by your provider. "There might be a program in your area," Jaffe explained. "You could agree to turn your air conditioning down (during peak hours) and they'd pay you something and take it off your electricity bill."
3. Change your electricity habits by avoiding heavy electricity use between 4 p.m. and 8 p.m. “Cool your house before you come home from work and then put put it off during that peak,” Jaffe said. “Or do a barbecue instead of using the oven.”

For more tips on how to keep your air conditioning bill down, check out how our meteorologists save money while staying cool.