Mills said during a news conference that Mainers will benefit from the project.
The project is currently under review by the Maine Public Utilities Commission. If it is approved, Maine would receive an incentives package to put money toward heat pumps for low-income families, electric car charging stations, and increased broadband access.
Mills said, that is on top of the projected millions in savings for electric ratepayers.
Opponents, including the Natural Resources Council of Maine, said the savings are insignificant compared to the potential climate impact. They said they disagree with any study claiming the project is safe for Maine.
"This project is a shell game for Hydro Quebec and CMP. They're going to take power that's already being generated, deliver it to some other customers, and instead deliver it to Massachusetts. We make a lot of money doing that but that doesn't help the climate," said NRCM spokesman Dylan Voorhees.
People on both sides of the issue said the final decision is still long from being made and that there will be many opportunities for public comment in the future.