By Avi Salzman

A remarkable stretch of extreme cold weather has tested America's electrical grid in the last two weeks.

The grid has passed the test so far, as power plants have ramped up around the country to meet rising demand, and resources such as large grid-scale batteries proved crucial. But it is also clear that reliability concerns are growing, and will only get worse as more AI data centers hook into the system.

There are already 20 additional gigawatts worth of power demand on the grid this winter as compared with last winter, the equivalent of 20 large nuclear reactors. In the next decade, peak power demand could soar by a stunning 224 gigawatts, the North American Electric Reliability Corp warned last month. And regulators warn that the spread of round-the-clock data centers mean that winter demand peaks will soon rival summer peaks.

Winter Storm Fern, the massive snow and ice storm that marked the start of the cold spell on Jan. 22, caused power outages for more than one million households. But those outages were related to the distribution system -- the electric wires in people's neighborhoods, not the power plants and large transmission lines that make up the larger grid.

"There were no bulk power-related outages," said Rob Gramlich, president of consultancy Grid Strategies. "All the power outages, which are always terrible and sometimes tragic, were related to local downed distribution lines."

During the storm and in the days afterward, operators of the nation's electric grids went to great lengths to keep the lights on. They asked some electricity users to reduce power usage to make sure the grid didn't get overloaded and called on so-called peaker plants to ramp up output to meet rising demand.

In the nation's largest grid network, known as PJM, the operator asked data centers and other large electricity users that own backup power to be ready to use their backup generators if the grid got into an emergency situation. They didn't end up having to force the companies to use those generators.

In that sense, the storm was a success story. Unlike similarly extreme storms four and five years ago, the system held up. Some resources operated at remarkably high levels. The nuclear reactors owned by Constellation Energy, which owns more nuclear generation than any other company, operated at an average capacity factor of 98.8% last week, meaning that they were producing power at their maximum possible output.

The strong performance of nuclear plants led to a unique phenomenon in some areas with a lot of reactors. In parts of Illinois, for instance, consistent nuclear generation and limited transmission lines to move it out of state caused power prices to actually fall below zero at times when prices were soaring elsewhere.

In Texas, a surge in large-scale battery installations made the grid more resilient during the storm. The state had 16.6 gigawatts worth of battery capacity at the end of 2025, up from less than 1 gigawatt five years ago. At critical moments over the past two weeks, batteries provided more power to the grid than five large nuclear reactors, keeping the lights on during times when other resources such as solar panels weren't working.

And, unlike during Winter Storm Uri in 2021, thermal power sources held up, too. The state mandated plants and wells to be "weatherized" to keep them operating during cold spells.

"The gas, coal and nuclear fleet was all significantly more reliable this time around," wrote Wood Mackenzie analyst Stephen Ryan.

In New York, which came close to breaking decades-old cold weather records in the past week, some old natural gas plants failed to operate on high-demand days. Solar panels were also largely ineffective, because so much snow and ice had collected on them that they could no longer draw power from the sun, according to the New York Independent System Operator, or ISO, the state's grid operator.

But the state did have more than enough power to get through the storm. The New York ISO asked dozens of large electricity users including manufacturers to ramp down their power usage on certain days to help make sure there was enough power.

Kevin Lanahan, a senior VP at the New York ISO, said in an interview that the state will need more electricity generation in the years ahead, in part because of data centers and the electrification of buildings. Some of the power plants that New York is relying on are at least 70 years old. And dispatchable resources like natural gas plants are being retired and replaced by solar and wind systems that operate intermittently.

New York City and Long Island face a reliability deficiency as soon as next summer.

"We are starting to see the system show signs of that demand growth strain, and need to add additional resources beginning now in order to accommodate and fill in the gaps," Lanahan said.

While resources like offshore wind farms and a new power line from Quebec should help add power in the coming months, new natural gas plants will also likely be necessary.

"We're going to need some kind of resource that is dispatchable, meaning we call on it and we know it's there and we can control it to get us through a period of demand growth. That is predominantly fossil fuel fired generation," Lanahan said.

Write to Avi Salzman at avi.salzman@barrons.com

This content was created by Barron's, which is operated by Dow Jones & Co. Barron's is published independently from Dow Jones Newswires and The Wall Street Journal.

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February 05, 2026 19:10 ET (00:10 GMT)

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