Electricity prices are heavily regulated. The largest increase I can find from a short search is around 20% for some customers in New Jersey. The average year over year increase is closer to 6%

Unexpectedly high electricity bills are almost always from actual usage. Unexpectedly high winter electricity bills are usually from resistive electric heating in one way or another.

You didn’t mention their normal December bill in this exact house, which is an important piece of information.

One of the families mentioned heats their home with natural gas.

I suspect they got slammed with an alternative energy supplier that charges abusively high rates.

With that said, the total cost to the consumer of electricity is 3X what it was 20 years ago, and I am in one of the cheapest markets.

You are part of the PJM. Read into what the "Fuel Adjustment" actually is. Yes, prices are regulated, but if your area is short of power, they can buy it from the PJM, usually from other sources they own, at "market" rate not regulated rate.

The Fuel Adjustment is the legal loophole difference in the regulated rate vs the market rate. A few scheduled maintenance windows and oh look, we are short power.

Texas is really different, it could be from there.