The Maine Public Utilities Commission on Thursday opened an investigation into the design and operation of the state’s electric distribution system.

“To address climate change in the years ahead, we will be placing new demands on our electric distribution system, and we must assess how to modernize the grid at the lowest cost for Maine people,” PUC Chairman Philip Bartlett said in a statement. “Recent issues related to interconnection of distributed resources highlight both the challenges we face and the urgency of the need for effective planning.”

On Feb. 11, the PUC opened a separate investigation into the interconnection practices of Central Maine Power (CMP).

Maine Gov. Janet Mills on Feb. 8 sent a letter to Bartlett asking for the investigation into CMP, saying she was dismayed by reports that the utility would need to upgrade more than 100 substations in order to complete existing interconnection agreements. Mills also asked the PUC to conduct a broader review of the grid to ensure it can handle growth of renewables and distributed energy resources. (See Lawmakers Chase Affordability in Energy Transition in Maine.)

CMP must respond to the PUC by Friday regarding concerns that its recent notices to customers about changes to interconnection costs jeopardizes “hundreds of millions of dollars in investment … for Maine homeowners and businesses,” according to the PUC’s notice of filing.

The PUC will retain experts to prepare a report about the current design and operation of Maine’s distribution grid. It will follow up with a formal investigation so stakeholders can comment on the report’s findings. The commission did not provide a timeline for when the report will be released.