A developer wants to build the state’s largest solar-electric project at an abandoned Navy radar site in Hancock County, but the venture hinges on the Maine Legislature passing a proposed law aimed in part at creating financial incentives for solar power.

Gouldsboro Solar LLC will announce Wednesday that it has signed a letter of intent with The Jackson Laboratory in Bar Harbor to sell the power from a 2.8 megawatt solar installation to the biomedical research lab. The project would feature 9,500 panels covering roughly 12 acres at the former Navy base. It would generate enough power each year to serve 500-600 average Maine homes.

But for the $9 million project to move forward, a bill already submitted to require electricity suppliers to include new solar generation in their power portfolios must pass the Legislature this session. The measure would gradually raise the required share of new solar power to 2.5 percent of utilities’ renewable energy portfolios by 2021.

The bill also would create renewable energy credits for solar power, a trading system by which credits could be sold to power suppliers to meet the growing portfolio requirement. A similar program in Massachusetts has led to 182 large, utility-sized solar projects and is critical for securing lenders, said Kim Kenway, president of Gouldsboro Solar and a Portland resident.

“We need to have a long-term contract (with a buyer) at a specified rate to attract financing,” Kenway told the Portland Press Herald. “The reason we don’t have any large-scale projects in Maine is because we don’t have a solar renewable energy credit program.”

The timing of the Gouldsboro announcement will likely sharpen debate over a bill sponsored by Rep. Sara Gideon, D-Freeport, who serves as House assistant majority leader. The bill is expected to have a public hearing within the next few weeks before the committee that handles energy matters. Kenway plans to testify at the hearing and lay out the project’s benefits.

Advocates say solar power makes sense for ratepayers because renewable energy costs are stable over time. By contrast, natural gas and oil prices fluctuate, and are expected to rise.

The bill is likely to draw opposition from Republican leaders, who generally oppose financial incentives and other subsidies for renewable energy. That outlook is shared by Gov. Paul LePage, who has come out against any incentives that he believes will increase electric rates.

The proposal comes as the falling price of solar-electric panels and the advent of efficient electric heat pumps have Maine home and business owners taking a fresh look at the potential of energy from the sun. But grid-scale projects are rare. The largest Maine solar project to date was completed last year at Bowdoin College in Brunswick, a 4,420-panel array rated at 1.2 megawatts. The Gouldsboro solar project would have more than twice that output.

Kenway declined to specify the kilowatt-hour rate, the duration of the contract or what percentage of the lab’s power needs the project would supply. But John Fitzpatrick, Jackson Lab’s senior facilities director, said the lab wanted to add renewable power to its energy supply and to support solar.

“The pure economics of the deal just make sense,” he said in a written statement. “This will allow us to lock in the purchase of a significant portion of our power needs at a low fixed rate for a very long period.”

The project would be located in the coastal village of Corea, part of the town of Gouldsboro. The panels would be mounted on racks set into concrete. The remote site contains several derelict buildings and isn’t likely to be redeveloped anytime soon.

“The Navy radar site has gone unused for over 15 years,” Gouldsboro Town Manager Eve Wilkinson said in a written statement. “It’s wonderful to think that we could add a large-scale, non-polluting power project to our town and, of course, to our town tax rolls.”

The bill has the support of at least two Republican lawmakers. Sen. Tom Saviello of Wilton and Rep. Richard Malaby of Hancock are co-sponsoring Gideon’s bill.

“With her bill in place,” Malaby said in a written statement, “we can begin to stimulate construction jobs and property taxes in rural areas such as my district, while at the same time adding an environmentally sound, zero-commodity-cost resource to our state’s power mix.”

The project would be built by ReVision Energy of Portland, the state’s largest solar installer. The work would generate roughly 35 construction jobs, according to ReVision. It would feed power into the Emera Maine local distribution grid.

The Gouldsboro project has a tight time line. To succeed, it must be completed by the end of 2016 to take advantage of a 30 percent federal tax credit for solar panels that is set to be cut back by the end of next year, unless it’s renewed by Congress. The company hopes to get started this fall, if Gideon’s bill passes and the Maine Public Utilities Commission approves a long-term contract with the Jackson Lab.

In his pitch to lawmakers, Kenway said he’ll make a comparison between the hydroelectric dams built in Maine during the past century and today’s solar potential. Building the dams required a high, upfront capital investment. But fully depreciated over time, they continue to provide power at a very low cost, since the “fuel” is free.

“In a sense,” he said, “they are gifts from our ancestors. In the same way, I believe that future Maine people will be grateful that we decided to take the long view and sponsor solar projects in our state.”

Correction: This story was revised at 10:53 a.m., April 8, 2015, to reflect that the proposed solar farm in Gouldsboro would generate enough power each year to serve 500-600 average Maine homes. An earlier version of this story contained an incorrect number.