Renewable power only provides about 10 percent of New England's electrical energy. The region's recent successes in reducing greenhouse gas emissions have come largely from a rise in the use of relatively clean-burning natural gas as the dominant power source.

But a play by Massachusetts to inject more renewable power into its electricity mix could reshape the entire region's energy landscape.

Sara Burns, the CEO of Central Maine Power, Maine's largest utility, says big, long-term renewable energy contracts being sought by Gov. Charlie Baker could mark a tipping point.

"Actually I think that's what Charlie Baker's trying to do here, make bigger plays to make a bigger difference on this," Burns says.

Dozens of developers are competing to offer Massachusetts the best price for long-term contracts to supply clean energy to hundreds of thousands of homes. But many of the projects face a challenge: convincing residents of northern New England that it's in their interest to host the Bay State's extension cord.

Burns is a close follower of Baker's plan because it's about more than just windmills, dams and big solar farms — it's about the high-voltage transmission lines her company specializes in, the kind needed to transport bulk electricity from remote locations to market. Central Maine Power is one of half a dozen companies bidding to build 100-mile or longer transmission lines that would run from or through the three northern New England states to link up to Massachusetts.

Billions of dollars are at stake, and each of the bidders is trying to highlight selling points — even as they fend off challenges from competitors and critics.

"There is a very large, committed activist base that is mobilized against this project," says Sam Evans-Brown, the host New Hampshire Public Radio's "Outside/In" podcast. For seven years, Evans-Brown has watched debate over a transmission proposal in his state called Northern Pass. It would carry electricity from Hydro-Quebec's massive dam system in Canada to Massachusetts, part of it buried under the White Mountains.

Evans-Brown says opponents want to know why their scenery should become the pass-through for Massachusetts' electricity needs.

"People who have businesses that would be impacted by the construction, and who believe that their business depends on tourists coming up to visit. There's a very famous pancake parlor that the owner came and gave impassioned testimony," Evans-Brown says, recalling a recent state hearing on the project.

"It will be devastational [sic] for us," Kathie Aldrich Cote, co-owner of Polly's Pancake Parlor in Sugar Hill, New Hampshire, said during that hearing. "Tourists will avoid the area and find other destinations to visit. They may not return for many years, if at all."

Just this year an alternative plan emerged in New Hampshire, called the Granite State Power Link. In contrast to several proposals that depend on existing Hydro-Quebec facilities, it would carry power from new wind and solar energy plants. Project director Joe Rossignoli says that means bigger reductions in greenhouse gas emissions, as called for by Massachusetts' climate policies.

"And that's significant because contracting with resources that are not in service yet and would only go into service to the extent that they won the bid, that really provides meaningful progress toward [Massachusetts'] Global Warming Solutions Act goals."

Kerrick Johnson is an executive at the Vermont Electric Power Company, which runs part of that state's grid. VELCO is backing a Vermont project called the TDI Clean Power Link. It would supply electricity to Massachusetts from Hydro-Quebec via a cable below Lake Champlain.

Johnson says TDI's strategy is working in Vermont -- few above-ground lines to draw opposition, and a helpful TDI agreement to subsidize transmission bills for Vermonters.

And Johnson says no matter who wins or what eventual configuration is chosen, the Massachusetts procurement is just a curtain-raiser for renewable efforts to come.

"Each of the six New England states are notoriously and gloriously independent, and the process isn't finished," Johnson says. "We'll see how it plays out."

The contract winners are expected to be announced in January. Meantime, another big play by Gov. Baker is coming up: long-term energy contracts relying almost exclusively on offshore wind turbines, which could be the next big thing for renewable power in the Northeast.

Offshore wind is still a relatively costly technology, but here's one advantage: You can build ocean-based windmills pretty close to the demand centers, and avoid all those long transmission lines.

This story comes via the New England News Collaborative, and was first published by Maine Public.