Central Maine Power residential customers who are disputing high winter electric bills will have to pay at least a portion of what’s due, following action Wednesday at the Maine Public Utilities Commission.

Maine’s Office of the Public Advocate had requested that CMP be barred from disconnecting home customers while the PUC conducts an investigation into why many of them have reported unexplanable charges, most starting in December.

The PUC has been contacted to date by roughly 1,500 customers about high bills.

But the PUC decided that such a blanket policy would be unreasonable and attempted to find a middle ground. Commission Chairman Mark Vannoy proposed a plan by which home customers who got bills after Nov. 1, 2017, with delivery charges 25 percent higher than the previous year, could pay what he called the undisputed portion of their bills. Basically, a customer that meets those standards would have to pay at least last year’s delivery usage levels, plus standard offer charges, if applicable, to remain connected.

The PUC has asked CMP to provide an explanation of this temporary policy in upcoming electric bills.

This concept made sense to Commissioner Bruce Williamson, who said it would help customers keep current with the bills.

“If CMP customers are using electricity,” he said, “then there’s something to be paid.”

Barry Hobbins, the Public Advocate, said after the deliberations that he was pleased with the outcome. State rules bar utilities from shutting off electric and gas service during the winter, but the so-called winter disconnect period ends April 15. So Hobbins was seeking some action before then.

“I think the commission acted prudently in limiting the class to home customers,” he said. “I went in asking for the moon, but hoping there would be a measured approach.”

Following the decision, CMP said it would review the specifics and work to make the adjustments as soon as possible.

“We feel the commission’s decision balances the need for our customers to pay for services they receive, while protecting them from the possibility they have been improperly billed,” said Gail Rice, a CMP spokeswoman.

The decision comes as utility regulators are in the midst of a two-pronged inquiry into what’s behind a spike in electricity bills for some CMP customers.

The PUC staff is in the process of pulling together data that includes electricity meters’ performance, billing system accuracy and CMP’s response to customers. On a second track, the agency is preparing to hire an independent consultant to delve deeper into the company’s billing system after a preliminary inquiry by staff failed to reveal why more than 1,000 CMP customers received inexplicably high utility bills this winter.

No precise timeline was given to conclude the full investigation. But the need to hire an expert and conduct the audit means that the process is likely to take several months.

Last month, CMP asked the PUC to extend the deadline past March 30 for responding to 23 questions and data requests. The PUC acknowledged that some of the requests, such as accounts and internal communications, are complex and involve large volumes of information. The agency then agreed to push the deadline out over a sliding timeline, with final information now due April 20.

Wednesday’s action came roughly three months after customers began contacting the PUC, the Public Advocate’s Office and media outlets to complain about inexplicably high monthly bills. In some instances, customers were reporting bills four times higher than for the same period last year.

At Wednesday’s deliberation, Vannoy stressed that if the probe finds a systemic problem on CMP’s end, customers will get refunds.

CMP had objected to the Public Advocate’s full request. 

“It is directly contrary,” CMP argued in a case filing, “to one of the three main purposes of (PUC rules) to assure the utility’s right to collect proper payment for utility services. In the event such payment is not made, CMP has the right and arguably the duty to pursue disconnection of those customers that do not pay their bills in a timely manner.”

When customers don’t pay their bills, CMP said, uncollectible costs are passed on to all customers.

CMP also said many reasons it disconnects customers, such as unauthorized use of electric service, have nothing to do with the ongoing dispute over high bills.