Power plant outages surged along the eastern United States on Sunday (26 January) as constricted natural gas supplies and frigid temperatures cut the electricity output of the region's generation fleet.

The PJM Interconnection, the largest US regional grid that serves 67 million people in the East and Mid-Atlantic, reported nearly 21 gigawatts of generation outages, with most of that capacity being forced offline. Those outages represented about 16% of PJM's Sunday afternoon demand of 127.4 GW.

On Sunday afternoon, PJM issued a pre-emergency order mandating that some customers in its curtailment program curb their electricity use. Customers in the program get paid to curb their electricity during critical periods.

PJM's order sought to ease an upswing in demand in PJM's territory while asking some generator operators to preserve their run time for colder weather and higher electricity demand later in the week.

Without native supplies of natural gas, the Eastern seaboard relies on a pipeline network that is historically constricted during extended bouts of frigid weather, said Pieter Mul, a grid expert and associate partner at PA Consulting's energy and utilities practice.

Domestic demand of natural gas, net of exports, is estimated at 146.7 Bcf/d, down 3.6 Bcf/d compared to Saturday and ranks at No. 10 all-time.

"From a natural gas production and price perspective, the current US winter storm so far is less severe than prior storms such as Uri and Elliott of 2021, 2022, but the risk isn't over, with sustained cold lingering behind the storm," said Matthew Palmer, the head of Americas Gas Research at S&P Global Energy.

PJM's outages are higher than the grid planned, Mul said, adding that there is less flexibility in the PJM system than a few years ago because of power plant retirements and a surge in demand from data centres.

PJM's territory also is hurt by bottlenecks in its transmission system of high-voltage power lines, hindering the transfer from west to east. For example, cheap power in Illinois on Sunday - sometimes dipping into negative prices because of abundant wind energy - could not be moved to help out other sections of PJM.

As snow and sleet hit the major cities of Boston, New York, Philadelphia and Washington, DC, the power grid also lost access to solar power in the afternoon from an increase in cloud cover.