Maine Public Utilities Commission Chairman Philip Bartlett (center) answers questioins by reporters last year. He is flanked by commissioners Randall Davis (left) and R. Bruce Williamson. Credit: Lori Valigra / BDN

Maine’s utility regulator voted Tuesday to start an investigation into problems Central Maine Power had connecting solar projects to its grid.

The unanimous vote from the three-member Maine Public Utilities Commission was in response to a February request by the Maine Renewable Energy Association and the Coalition for Community Solar. Gov. Janet Mills, who is pushing a climate action plan that includes renewable energy, also asked the commission to launch an investigation after CMP said more than 100 substations may require costly and unexpected modifications to interconnect hundreds of megawatts of new solar projects across the state spurred by a 2019 law.

CMP drew heavy criticism in February after it contacted some solar suppliers to tell them of potential delays and extra costs to integrate their project into CMP’s existing grid. The utility later reversed course after public pressure, but the issue is still gaining traction among the solar community and lawmakers as the state moves to meet clean energy goals.

The company will “fully cooperate” with the commission’s investigation, CMP spokesperson Catharine Hartnett said.

CMP received more than 600 requests in less than two years to interconnect some 2,000 megawatts of new power onto its distribution network. That is 300 megawatts more than CMP’s system’s peak load now, she said, “creating significant technical challenges.”

“The overwhelming response to the changes in state policy has resulted in a dramatic influx of solar development,” Hartnett said.

The Natural Resources Council of Maine, a vocal critic of CMP, said the commission has had to step in to “hold CMP accountable for hindering solar projects in its territory.”

“Maine deserves a utility that is an active partner, not an obstacle, in the transition to a clean energy economy,” Sue Ely, a staff lawyer for the council, said.

The letter by the two solar groups called CMP’s “egregiously incompetent and jeopardizing hundreds of millions of dollars in investment.”

CMP responded to the complaint, but commission Chairman Phil Bartlett said the information provided to date “has not resolved the concerns” raised by the solar groups. He supported opening an investigation, and commissioners Randall Davis and R. Bruce Williamson agreed.

The investigation will cover whether CMP’s identification of a ground fault overvoltage issue as the problem was prudent and potentially look at whether the commission should issue any penalties.

The commission also will open a separate investigation to examine grid modernization and whether changes are needed to accommodate future distributed resources and loads. A third related case will look into smaller generation protocols to connect to the grid.

Correction: An earlier version of this story had an incorrect name for the Natural Resources Council of Maine.