The summer has long put pressure on the electrical networks. Now winter does that too.

For decades, electricity grid operators feared that rising energy demand on hot summer days would lead to power outages. They are now increasingly concerned about the coldest winter days.

Largely due to growing residential and commercial demand, and supply constraints due to aging utilities, many power grids are under greater strain in the winter. In 2033, compared to current levels, growth in winter electricity demand is expected to exceed growth in summer demand. the North American Electric Reliability Corporationa nonprofit organization that develops and enforces standards for the utility industry.

Just ten years ago, electricity consumption in winter was about 11 percent lower than in summer, according to the group. By 2033, that difference is expected to narrow to about 8 percent. And by 2050, winter demand could exceed summer electricity consumption.

“We see both summer and winter peaks growing, but we see winter peaks growing faster,” said Jim Robb, CEO of the reliability company. “The demand curve is shooting up very, very quickly.”

Years after the 2008 financial crisis, annual electricity demand was virtually 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 companies have built hundreds of large data centers, each of which can consume as much power as a small city, and as individuals have bought more electric cars and appliances. A major contributor in winter is the increasing use of electricity to power heating appliances in homes and businesses that previously used oil or gas furnaces.

Although generally very efficient, electric heat pumps become less efficient when the outside temperature is below 30 degrees Fahrenheit, Mr. Robb said. As a result, electric utilities have to work harder when it is very cold and during winter storms.

On January 17, as bitter cold engulfed many of the seven states it serves, the Tennessee Valley Authority struck highest peak demand for electricity ever. The public energy system, which has nine million customers, was able to cope with this thanks to improvements it made to meet higher winter demand. The previous record was set on August 16, 2007.

“We are already seeing higher winter peaks and more challenges in our region than with summer peaks,” said Aaron Melda, senior vice president for transmission and power at the authority.

PJM, the nation's largest network serving 65 million people in 13 states, also exceeded expected demand on Jan. 17, as snow, sleet and freezing rain blanketed the Mid-Atlantic. The system met that demand and supplied energy to adjacent grids. A year earlier, PJM needed help from its neighbors during a major winter storm.

U.S. power grids are also struggling because they import less power from Canada in the winter. Demand for electricity in that country is growing sharply, and a decline in rain and snow has reduced the supply of hydroelectric power plants, said Robert McCullough of McCullough Research, an energy consultancy based in Portland, Oregon.

Aged and poorly maintained U.S. power lines and utilities are another major problem, he said. The power grid that serves much of Texas collapsed during a 2021 winter storm, in part because natural gas pipelines and power plant equipment froze or malfunctioned. Nearly 250 people died because of the storm and power outages, state officials said.

“It's quite clear that we're entering a period where we don't know what's going to happen,” Mr McCullough said. “Electrification is clearly going to change and worsen this.”

Like many Americans, Michael Pittman had grown accustomed to the strain on the power grid caused by summer heat waves or storms. He lives just outside of Houston, where he works as general manager of Star Pizza, a restaurant with two locations in the city.

The 50-year-old restaurant's original storefront — where the dough and sauce for both stores are made — lost power during the 2021 storm.

“There was a very helpless feeling,” said Mr. Pittman, who has worked at the restaurant since 1994 and previously dealt with power outages during hot summer days and hurricanes. “Now it gives everyone that feeling of fear when you hear that a freeze is coming. The news immediately goes to the grid.”

The restaurant considered purchasing generators for backup power, but Mr. Pittman said that would cost too much. Instead, he's preparing for the worst when temperatures drop and hopes to continue operating from his second location, in an area where power outages are less likely to occur during bad weather.

“There are certain things you take for granted,” Mr. Pittman said. “The electricity grid is one of them.”

The electric grid faces many challenges as the country takes steps to reduce greenhouse gas emissions. And the growing demand for electricity in the winter makes much of that more difficult.

In much of the country, power grids are designed to meet high demand in the summer, when people turn on the air conditioners. As a result, utilities typically close some power plants and other parts of the electrical grid for maintenance and upgrades during the rest of the year.

High demand across multiple seasons could make it more difficult to repair and improve stressed and aging systems, according to energy experts.

The North American Electric Reliability Corporation believes that winter electricity use in New York and other northeastern states could exceed summer demand within six years. That would also mean higher electricity bills, which have been rising steadily in recent years. In November, the average American homeowner paid $162 for typical use of 1,000 kilowatt hours, up from $156 a year earlier, according to the Energy Information Administration.

“As more jurisdictions move to all-electric, you're going to see that peak change,” said Calvin Butler, CEO of Exelon, which owns regulated utilities in New Jersey, Maryland, Delaware, Pennsylvania and Illinois. “We are increasingly going to see a winter peak season.”

Mr Butler said he believed growing demand for electricity would require upgrades and additions to the grid to keep the lights on, including the continued use of certain fossil fuels.

Renewable energy sources such as solar panels and wind turbines produce less electricity in the winter, partly because there are fewer hours of sunshine and because wind and weather conditions are more variable. That is why Mr. Butler argues that the United States will have to continue using natural gas plants, which provide about 40 percent of its electricity.

“It just reinforces the need to have natural gas in the system,” Mr. Butler said. “You will need gas in the near future.”

Continuing to burn a lot of natural gas to produce electricity will obviously undermine efforts to reduce emissions of carbon dioxide and methane – two major greenhouse gases. But replacing gas is difficult because batteries and other energy storage technologies cannot currently provide enough energy for days at a reasonable price, although some experts think this will change in the future.

Utilities could also build more transmission lines to transport renewable energy from places where it is abundant to where it is needed, such as from large solar farms in the Southwest to the Midwest in the winter. But the approval of such projects can take many years.

“This is a lot of energy that we're talking about and trying to avoid,” said Mr. Robb of the Grid Reliability Corporation. “We need a technology that is widely available and that can provide the same kind of balancing services that we get from gas.”

Mr McCullough, the consultant, said the focus on more natural gas was short-sighted in part because gas-fired power stations were unreliable even in winter. He said grid operators and utilities should consider more distributed sources, such as rooftop solar, and better plan for growing winter demand in a way that allows the country to tackle climate change.

“The bottom line,” he said, “is that we're going to have both summer and winter peaks, and we're not predicting them.”