Grid operator PJM estimated that non-performance charges related to generating capacity shortfalls on Dec. 23-24 could be anywhere from $1 billion to $2 billion across the region, which reaches from the East Coast to the Midwest.

Temperatures across the region fell on December 23 and lasted into the morning of December 25 with record lows set in some areas.

PJM said in a preliminary report that it was “conservative” in developing operating plans for December 23. It said its forecast load was 126,968 MW and that it called for 155,750 MW in operating capacity for the day.

“Based on generator availability data submitted to PJM, we believed we had almost 29 GW of reserve capacity available to absorb load and generation contingencies and to support our neighboring systems.”

But, as reserves were called on, “a significant” portion of the fleet “failed to perform.”

By the evening of December 23, some 34,500 MW of capacity was unavailable across the region. That grew to around 46,000 MW by mid-morning on December 24.

PJM said that “over 92% of all outages were reported to us with less than an hour’s notice or with no notice at all.” At the depths of the shortfall, more than 23% of the generating capacity in PJM was unavailable.

Data showed that plant equipment and fuel supply issues made up the majority of outages over that period.

Forced outages included 32,473 MW of natural gas, 7,562 MW of coal, and 5,917 MW of nuclear, oil, solar, wind, and so on as of December 24.

In addition for forced outages, some 6,000 MW of steam generating capacity was called on but was not available. “The vast majority of these resources were gas-fired resources,” PJM said.

Pumped hydro storage generation also suffered as the high rates of generator outages limited PJM’s ability to replenish resources prior to the morning peak on December 24.

All totaled, PJM said it faced around 57,000 MW of generator unavailability for the morning peak on December 24.

PJM said it is conducting a full analysis of the December performance issues and that its findings could be available in April.

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