State officials are formally intervening to oppose a rate hike being sought by Central Maine Power Co.

The Governor’s Energy Office on Thursday filed for intervenor status in the Maine Public Utilities Commission’s deliberations on the increase proposal, which is forecast to raise a typical customer’s monthly bill by $10 a month by 2026. Intervenor status will allow the Governor’s Energy Office to participate more fully in the rate hike request hearings, beyond testifying against the increase.

CMP notified the Maine Public Utilities Commission in May that it would file the increase request this summer. The company, which distributes electricity to central and southern Maine, said the money from the hike will support efforts to make its system more resilient to storms, aid in restoring power faster when outages occur and enable more renewable power generators to hook into the electricity grid as the state moves to a cleaner-energy economy.

Gov. Janet Mills immediately vowed to oppose the rate hike, which she called “outrageous” because, she said, already-high electric rates are harming Maine families. At a time of high inflation, the rate hike “adds insult to injury,” she said in May.

Thursday, she said that while it’s important to make sure the electric system is resilient, “the timing of these costs must be balanced against the high costs – including already high energy prices – that are hurting Maine people and businesses right now.”

For an average home customer using 550 kilowatt-hours a month, the plan would increase a total electric bill by roughly $5 a month in 2023, and up to $2.50 a month in each of the following two years.

CMP officials acknowledged the impact of a rate hike at a time of high inflation, but said the utility needs to make investments to update the electric grid.

“CMP must continue to make smart system updates that improve reliability now and enable the company to successfully perform our role in helping Maine meet its climate change goals,” Joseph Purington, the company’s president and chief executive, said at the time.

Mills said opposition to the rate hikes is part of her administration’s overall energy policy that includes an increased focus on renewable energy projects and increased oversight of the state’s electric utilities. Some legislators have been pushing to have the state take over the investor-owned utilities, but Mills has resisted those plans, saying more study is needed to determine the impact on Mainers and businesses.

Our Power, a group supporting an effort to put a buyout of the two utilities on the ballot, applauded the administration’s decision to intervene, but said rate increases for investor-owned utilities are difficult for state authorities to turn down.

“A customer-owned utility could make these investments at half the cost to the average ratepayer,” Andrew Blunt and Seth Berry said in a statement. Our Power says that a customer-owned utility would save consumers money because it wouldn’t need to provide shareholders with a return on their investment.

Blunt is executive director of Our Power and Berry is a state legislator who is one of the leaders of the effort to engineer a consumer buyout of the two utilities.