The Winter Peak Is Coming

The electric grid is built for heat. The days when the system is under the most stress are typically humid summer evenings, when air conditioning is still going full blast, appliances are being turned on as commuters return home, and solar generation is fading, stretching the generation and distribution grid to its limits.

But as home heating and transportation goes increasingly electric, more of the country — even some of the chilliest areas — may start to struggle with demand that peaks in the winter.

While summer demand peaks are challenging, there’s at least a vision for how to deal with them without generating excessive greenhouse gas emissions — namely battery storage, which essentially holds excess solar power generated in the afternoon in reserve for the evening. In states with lots of renewables on the grid already, like California and Texas, storage has been helping smooth out and avoid reliability issues on peak demand days.

The winter challenge is that you can have long periods of cold weather and little sun, stressing every part of the grid. The natural gas production and distribution systems can struggle in the cold with wellheads freezing up and mechanical failure at processing facilities, just as demand for home heating soars, whether provided by piped gas or electricity generated from gas-fired power plants.

In its recent annual seasonal reliability assessment, the North American Reliability Corporation, a standard-setting body for grid operators, found that “much of North America is again at an elevated risk of having insufficient energy supplies” should it encounter “extreme operating conditions,” i.e. “any prolonged, wide-area cold snaps.”

NERC cited growing electricity demand and the difficulty operating generators in the winter, especially those relying on natural gas. In 2021, Winter Storm Uri effectively shut down Texas’ grid for several days as generation and distribution of natural gas literally froze up while demand for electric heating soared. Millions of Texans were left exposed to extreme low temperatures, and at least 246 died as a result.

Some parts of the country already experience winter peaks in energy demand, especially places like North Carolina and Oregon, which “have winters that are chilly enough to require some heating, but not so cold that electric heating is rare,” in the words of North Carolina State University professor Jeremiah Johnson. "Not too many Mainers or Michiganders heat their homes with electricity,” he said.

But that might not be true for long.

New England may be cold and dark in the winter, but it’s liberal all year round. That means the region’s constituent states have adopted aggressive climate change and decarbonization goals that will stretch their available renewable resources, especially during the coldest days, weeks, and months.

The region’s existing energy system already struggles with winter. New England’s natural gas system is limited by insufficient pipeline capacity, so during particularly cold days, power plants end up burning oil as natural gas is diverted from generating electricity to heating homes.

New England’s Independent System Operator projects that winter demand will peak at just above 21 gigawatts this year — its all-time winter peak is 22.8 gigawatts, summer is 28.1 — which ISO-NE says the region is well-prepared for, with 31 gigawatts of available capacity. That includes energy from the Vineyard Wind offshore wind project, which is still facing activist opposition, as well as imported hydropower from Quebec.

But going forward, with Massachusetts aiming to reduce emissions 50% by 2030 (though state lawmakers are trying to undo that goal) and reach net-zero emissions by 2050 — and nearly the entire region envisioning at least 80% emissions reductions by 2050 — that winter peak is expected to soar. The non-carbon-emitting energy generation necessary to meet that demand, meanwhile, is still largely unbuilt.

By the mid 2030s, ISO-NE expects its winter peak to surpass its summer peak, with peak demand perhaps reaching as high as 57 gigawatts, more than double the system’s all-time peak load. Those last few gigawatts of this load will be tricky — and expensive — to serve. ISO-NE estimates that each gigawatt from 51 to 57 would cost $1.5 billion for transmission expansion alone.

ISO-NE also found that “the battery fleet may be depleted quickly and then struggle to recharge during the winter months,” which is precisely when “batteries may be needed most to fill supply gaps during periods of high demand due to cold weather, as well as periods of low production from wind and solar resources.” Some 600 megawatts of battery storage capacity has come online in the last decade in ISO-NE, and there are state mandates for at least 7 more gigawatts between 2030 and 2033.

There will also be a “continued need for fuel-secure dispatchable resources” through 2050, ISO-NE has found — that is, something to fill the role that natural gas, oil, and even coal play on the coldest days and longest cold stretches of the year.

This could mean “vast quantities of seasonal storage,” like 100-hour batteries, or alternative fuels like synthetic natural gas (produced with a combination of direct air capture and electrolysis, all powered by carbon-free power), hydrogen, biodiesel, or renewable diesel. And this is all assuming a steady buildout of renewable power — including over a gigawatt per year of offshore wind capacity added through 2050 — that will be difficult if not impossible to accomplish given the current policy and administrative roadblocks.

While planning for the transmission and generation system of 2050 may be slightly fanciful, especially as the climate policy environment — and the literal environment — are changing rapidly, grid operators in cold regions are worried about the far nearer term.

From 2027 to 2032, ISO-NE analyses “indicate an increasing energy shortfall risk profile,” said ISO-NE planning official Stephen George in a 2024 presentation.

“What keeps me up at night is the winter of 2032,” Richard Dewey, chief executive of the neighboring New York Independent System Operator, said at a 2024 conference. “I don’t know what fills that gap in the year 2032.”