Bangor Natural Gas construction technicians replace a 10-foot section of a 1" service line on Hammond Street in July 2017. Credit: Linda Coan O'Kresik / BDN

Bangor Natural Gas is seeking the state’s permission to raise its distribution rates beginning on April 30, according to a letter sent to customers.

The average residential customer could see monthly bills grow by 20 percent, or more than $24, under the plan the Bangor-area utility said it plans to file with the Maine Public Utilities Commision. A medium commercial customer could see their average monthly bill grow by a smaller percentage, 8.4 percent, but by a larger dollar amount — more than $173. Other classes of customers would see a variety of rate increases.

Andrew Barrowman, the company’s sales and marketing manager, said the increase was necessary because of the growing costs required to operate its natural gas distribution system, which serves 7,500 customers in Bangor, Brewer, Orono, Veazie, Old Town and Hampden, as well as Bucksport, Searsport and Lincoln. Most of its current customers are residential, with about one-fifth being commercial or industrial customers.

Bangor Natural Gas’ costs have increased as its customer base has grown in recent years, Barrowman said. The customer base has more than doubled since 2012, when the company had 3,600 customers.

It is the first increase Bangor Natural Gas has proposed in 10 years, and it would require approval from the Maine Public Utilities Commission.

“Proposing to the MPUC that we increase customer rates is not something we take lightly,” Bangor Natural Gas said in its letter to customers.

Bangor Natural Gas filed a notice of intent with the Public Utilities Commission to request a rate increase on Jan. 29. It planned on filing the rate increase proposal itself on or shortly after March 29.

The commission’s process for evaluating the rate increase request could take as long as nine months, the company said.