AUGUSTA, Maine (AP) Democratic Gov. Janet Mills is asking state utility regulators to investigate why Central Maine Power has alerted solar operators that they’re going to have to pay extra to connect to the grid.

CMP sent emails to the developers of solar power projects late last month warning of additional costs because of unanticipated problems in connecting the projects to the grid.

Mills told Public Utilities Commission Chairman Philip Bartlett that it’s “deeply regrettable” that CMP did not anticipate the problems.

Maine is experiencing a boom in solar projects but they depend utilities to integrate them into the existing power grid.