Maine utility regulators are in the midst of an investigation into Central Maine Power's metering and billing systems.
Some customers say that as problems persist, they are stuck in the middle.
CMP customer Mike Harvey says he knows what the electricity bill should be for his Winthrop home.
He said the bill typically runs between $500 and $600 but when he recently received a bill for less than $50, he knew something wasn't right.
That low bill for May was followed by two more low bills, each for about $26 for June and July. Harvey said he contacted CMP to ask why his bills were all of a sudden so low.
"CMP told me they were having a billing issue and they were estimating my bill," he said.
But according to the power company's website, usage estimates should be based on the customer's usage during the same month last year.
CMP spokesman Gail Rice said that while the company prefers not to discuss specific customer situations, she wrote that CMP has "identified a couple of system errors that may have affected a small number of customers."
She said those customers do not use smart meters but rather analog ones.
She says one error incorrectly estimated usage at zero instead of basing it on the year before and that a second error prevented loading actual readings into the system and that both problems have been fixed.
State regulators are investigating the company's metering, billing and customer communications after a record number of complaints about high bills and unexplained usage.
After months of low bills, Harvey's most recent bill ow shows a big balance -- more than $3,300.
"I'm waiting for my next one to come in. I'm curious to see what that usage will be," he said.
CMP says it understands concerns from customers who had low estimates and now might not be able to pay in full right away.
The company suggests that those customers give them a call.