Electric utilities, which designed their system to meet peak demand in sizzling weather, are straining to keep up during the cold.

For decades, managers of electric grids feared that surging energy demand on hot summer days would force blackouts. Increasingly, they now have similar concerns about the coldest days of winter.

Largely because of growing demand from homes and businesses, and supply constraints thanks to aging utility equipment, many grids are under greater strain in winter. By 2033, the growth in electricity demand during winter, compared with the current level, is expected to exceed the growth in demand in summer, according to the North American Electric Reliability Corporation, a nonprofit organization that develops and enforces standards for the utility industry.

Just 10 years ago, winter electricity use ran about 11 percent less than in summer, according to the group. By 2033, that gap is expected to shrink to about 8 percent. And by 2050, winter demand could surpass electricity use in the summer.

“We’re seeing both summer and winter peaks growing, but we’re seeing winter peaks growing faster,” said Jim Robb, chief executive of the reliability corporation. “The demand curve just shoots up very, very quickly.”

For years after the 2008 financial crisis, annual electricity demand was essentially flat. The Obama administration promoted energy efficiency as a way to address climate change, and consumers used less electricity to save money.

But that trend has reversed in recent years as businesses have built hundreds of large data centers, each of which can use as much power as a small city, and as individuals have bought more electric cars and appliances. A major contributor in the winter is the increasing use of electricity to power heaters at homes and businesses that previously used oil or gas furnaces.

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