Nearly 10 years after Massachusetts announced plans to buy 1.2 gigawatts of carbon-free hydropower from Canada, the clean electrons are finally set to start flowing into the state.

As soon as this Friday, the New England Clean Energy Connect transmission line could begin commercial operations.

The 145-mile project, extending from the Canadian border to the southern Maine city of Lewiston, will function as something like an enormous extension cord, plugging the New England grid into a supply of electricity generated by energy giant Hydro-Québec. The new supply is expected to save the average residential customer in Massachusetts $18 to $20 per year and move the state closer to its goal of net-zero emissions by 2050.

“This is a significant moment for clean energy in New England,” said Phelps Turner, director of clean grid for the Conservation Law Foundation.

Avangrid, the developer of the transmission line, told Maine utility regulators earlier this month that operations are scheduled to begin on Jan. 16. Work is underway to meet that target.

“Teams are busy on both sides of the U.S.-Canada border,” said Hydro-Québec spokesperson Lynn St-Laurent. ​“We have been actively testing the equipment for the past several weeks.”

Following a tumultuous year for clean energy projects, the completion of the controversial transmission line is both a rare triumph and a case study in the challenges of balancing decarbonization and the preservation of wild lands. It’s also an uncommon example of transmission getting built in the U.S., where it has proven difficult to construct the massive power lines needed to deliver new electricity supply to population centers.

The project has its roots in a 2016 Massachusetts law that called for the state to procure 1.2 gigawatts of Canadian hydropower, or other renewables, and 1.6 gigawatts of offshore wind energy. The first idea for importing power from the north involved working with a planned 192-mile transmission line through New Hampshire. However, the project was scuttled in 2019 by public outcry against the prospect of chopping a path through some of the state’s treasured forests.

Massachusetts then looked east, to Maine, to find a route for the transmission line. Similar objections quickly arose, with opponents in the state filing a series of legal challenges. In 2021, Maine voters approved a ballot referendum effectively blocking the project. Work froze until August 2023, a few months after a jury unanimously ruled the project could move forward.

The delays spiked the project’s price tag. Before the line could start providing power, the developer, state regulators, and utilities had to come to an agreement about how those costs would be covered. In early 2025, they settled on terms that increased the price utilities would pay by a total of about $521 million, but ensured consumers would still see savings.

“The project faced many challenges over many years, and it survived all of them,” Turner said.

In addition to the modest monthly savings expected for Massachusetts utility customers, the influx of hydropower should keep rates down for consumers throughout New England by pouring lower-cost electricity into the market that will put downward pressure on prices, right at a time when rising energy bills have become a major issue, Turner said.

Questions remain, however, about how much new power the project will actually bring to the New England grid.

Hydro-Québec already sends power into the region on a separate transmission line, though these exports have decreased in recent years, even stopping almost entirely for a period in 2025. It’s possible that meeting its commitment to deliver along the New England Clean Energy Connect line will mean Hydro-Québec chooses to send less power along other pathways, said Dan Dolan, president of regional trade group the New England Power Generators Association. The net increase in clean power may be lower than anticipated.

“The change in flows over the last several years, particularly in 2025, do not leave me optimistic that Canadian hydro is here to save the day,” Dolan said.