Over three quarters of a million Massachusetts households were behind on their utility bills at the end of of December, according to a report published Wednesday by the National Consumer Law Center, a Boston-based nonprofit.

And many of those homes could have their gas or electricity shut off in a few weeks. The state’s annual winter moratorium on shutting off utilities for low-income residents who haven’t paid their bills expires in mid-March amid sky-high gas and oil prices.

Massachusetts utility customers collectively owed nearly $675 million in overdue gas and electric bills. It’s a figure that has actually been falling since spring of 2021, but it’s still significantly more — roughly $100 million more — than before the pandemic began.

“We have seen a fairly explosive growth since COVID hit in the number of people who are significantly behind in their bills, and therefore face risk of termination when the moratorium ends in a couple of weeks,” said Charlie Harak, a staff attorney with the NCLC.

The winter moratorium on shut-offs only applies to lower-income residents, whose income is at or below 60 percent of the state’s median income.

But the biggest jump in overdue bills came from people whose income was higher prior to the pandemic, and for whom there’s no moratorium on shut-offs.

As of the end of December, 281,000 of those households were more 90 days behind on utility bills — about 40,000 households more than before the pandemic.

“[That’s] in part because many of those customers had been current on their bills until COVID devastated their lives,” Harak said.

A spike in natural gas prices this winter has made things even more challenging. According to Eversource, the natural gas price in November for the company’s customers was roughly 17 percent higher than the previous winter.

“The customer who is 90 days or more behind on their bills, they owe over $1,000 on average,” Harak said. “They are in a big hole.”

A spokesperson for National Grid says the utility company has been offering customers a deferred payment agreement since the start of the pandemic, which allows them to pay overdue balances over time. The company says its increased the number of customers getting discounted rates by 10 percent over the pandemic, and has increased the amount of arrears that can be forgiven.

On top of the more than $120 million in federal money the state received for the Low Income Home Energy Assistance Program this year, Massachusetts got an additional $187 million for home heating assistance funding from federal pandemic relief funds. The state used half of that to help households pay off utility debts last summer and is holding the other half to help with bills next winter, according to Harak.

“Anyone who is having a hard time paying their utility bills — whether gas or electricity — should know that the fuel assistance program is available, and they should apply as soon as possible,” Harak said.

Details on applying for help are online here.