About 1,500 customers are facing demands for payments of $500 or more.

PORTLAND, Ore. — More than 1,000 Portland General Electric customers are facing huge bills after a mistake by the power company.

Last year, PGE upgraded it’s computer billing system, and that led to some customers getting inaccurate power bills.

Kevin Carty is a PGE customer. He said it’s not often a business bills a customer incorrectly, then comes back nearly a year later and demands the customer pays for their mistake.

“It doesn't solve the sour taste in the mouth, as a customer, that I’m ending up paying for a mistake on their part,” Carty said.

Carty got a call out of the blue from a PGE representative, who said the company didn’t collect all the money Carty owed.

“I said, ‘OK, what’s that look like?’ And she said, well in your case, it’s going to be close to $600.”

The problem started when PGE did a massive computer system upgrade last May. That upgrade had a few hiccups with the equal pay program, a billing program PGE uses that averages out customers’ yearly monthly bill, and charges customers the same amount every month.

Steve Corson with PGE said the advantage of the system is customers get predictability.

“You know roughly what your bill is going to be every month,” he said.

The upgraded billing system stopped doing what’s called “true-ups,” when the system checks customers’ power usage to calculate their bill. And now, about 1,500 customers are facing demands for payments of $500 or more. There are some customers who owe more than double what their equal pay bill would have been.

Bob Jenks with the Oregon Citizens Utility Board said accurate bills are a fundamental part of utility service.

“No customer should get a call from the utility saying, ‘Oh, by the way, you owe two, three, four-hundred dollars that’s never appeared on your bill,’” he said.

Jenks said when customers pay their power bill, one of the things they pay for is not only power service, but accurate billing, too.

“This is really coming to customers without any expectation or knowledge that this is going to happen, and it really is unfair,” Jenks said.

Carty said its PGE’s mistake and fixing it shouldn’t be lumped on the customer.

“Somebody made a decision that just isn’t right,” he said. “It just didn’t sit right with me.”

PGE is now calling every customer affected.

“We may have surprised some people and we are truly sorry about that,” Corson said.

Still, PGE says the power was used and customers must pay for it. PGE is offering to spread out the unexpected payments over a two-year period.

That still isn’t acceptable for Carty.

“I’d like to see them take responsibility for the mishap on their part, and not put it on the shoulder of their customers,” he said.

The Public Utility Commission has ruled on this issue in the past, saying despite the inaccurate billing, customers did use the power and are responsible to pay for it.