As the state legislature enters the home stretch on a major new climate bill, a familiar battle line is being drawn, pitting real estate developers and climate advocates against each other on a crucial question: Should communities be allowed to ban fossil fuel hook-ups for new buildings?

That question concerns just one aspect of a wide-ranging bill. The measure will would reconcile an ambitious House bill focused on developing offshore wind with a Senate bill that includes a broader array of climate provisions, including measures to increase the number of electric vehicles on the road, make public transportation greener, and pour money into the development of clean energy.

But in the final days of negotiating the bill before it goes to the governor’s office, a contentious debate has arisen over a provision in the Senate bill that would allow 10 communities to ban fossil fuel hookups in new buildings.

It’s an issue that has dogged the state for years, since Brookline first attempted to ban new fossil fuel hookups in 2019. Attorney General Maura Healey subsequently advised that such a step violated state law. Since then, several communities have attempted to pass so-called “gas bans” via home rule petitions, but none have been implemented.

The measure proposed in the Senate bill would launch a pilot of sorts, allowing Cambridge, Newton, Brookline, Lexington, Arlington, Concord, Lincoln, Acton, Aquinnah, and West Tisbury to opt in.

Developers and fossil fuel interests are pushing back hard. In an email blast to its members Thursday, NAIOP Massachusetts, a lobby for developers and building owners, wrote: “FINAL CLIMATE BILL ANTICIPATED TO INCLUDE FOSSIL FUEL BANS – NAIOP NEEDS YOUR HELP.”

The response from climate groups was swift.

“We know that the gas industry and their allies are organizing and communicating with the lawmakers, opposing what we want,” wrote organizers from Mothers Out Front, on a web page that urges followers to press legislators to support the ban, along with other priorities.

As of noon Friday, 250 members had used the website to send emails to legislators, according to Andra Rose, who coordinates the legislative team for Mothers Out Front.

“Now is the time to stop it,” Rose said, referring to the state’s reliance on natural gas. “The way to stop it is with the lowest-hanging fruit: New buildings, and buildings that are going through major renovations.”

Tamara Small, the CEO of NAIOP, said there are risks to switching off fossil fuels entirely, including concerns that electrified sources of heat wouldn’t be adequate on the coldest days. She said full electrification could stress the grid, and that it would increase costs for builders and homeowners.

“In a nutshell, while our members are successfully pursuing electrification for all product types, only hybrid electrification is feasible at this time, particularly for office and lab properties,” she said via e-mail, referring to a combination of gas and electric.

Christine Milligan, spokeswoman for National Grid, agreed, calling hybrid electrification “the least costly, most effective way for our customers and the Commonwealth to achieve our net zero goal.”

But climate advocates — as well as Senator Mike Barrett, a Democrat from Lexington, the author of the Senate bill — said exemptions would be allowed for facilities like labs and hospitals, and that across the region, fully-electric buildings are coming online and proving that they can withstand the cold of a New England winter.

They also question whether it actually costs more to build a fully-electric building.

According to a report commissioned by the state Department of Energy Resources, thanks in large part to new rebates from Mass Save, it usually costs less to build fully electric. Compared to a house built according to the base building code, for instance, a fully electric, five-bedroom single-family home in Worcester would save a builder $20,062 and save the buyer $548 a year.

A large gas home, meanwhile, would cost $3,184 more than the base for the builder, while saving the buyer $302 a year compared to a house built to the base building code. An all-electric small single family home would provide even greater savings. A small single family home using gas, meanwhile, would cost a builder nearly $8,000 more than a house built to the base code, and would cost the homeowner $496 a year. A 6-unit multifamily also offered savings if all-electric.

According to the analysis, the only example that did not offer savings if it were fully electric was a townhouse, which could cost a builder $11,492 compared to the base code, but would still save the buyer $316 a year.

Advocates note that, unlike the situation when Brookline first proposed its ban in 2019, cities around the country are beginning to enact gas bans.

“This isn’t some sort of fanciful concept that no one is able to do,” said Kyle Murray, a senior policy advocate at the Acadia Center, a clean energy advocacy organization. “New York City‚ one of the largest cities and most economically powerful, just passed a ban on new fossil fuel hookups. New York is considering doing it statewide. DC is in the process of working on a ban on new fossil fuel hookups. This is not something that is out of left field, crazy, not able to be done.”

In Cambridge, housing advocate Becca Schofield, who co-chairs the non-profit A Better Cambridge and is an affordable housing developer, said she supports the fossil fuel banning measure, as long as the needs of low and moderate income people aren’t forgotten.

“The fear is that this would further limit affordable housing opportunities,” she said, adding that she would like to see exemptions for affordable housing developments. “Not that they’ll use it,” she said. “In my own work, I’m not making any new gas connections.”

The legislature technically has until the end of the month to finalize the bill, but it must send it to Governor Baker’s office by Thursday if it wants to ensure legislators will have time to override a veto from the governor’s office, should one come.

In late 2020, concerns from the real estate industry about the potential impacts on the price of housing development contributed to Baker vetoing the state’s landmark climate bill mandating that the state slash emissions to half of 1990 levels by 2030 and get to net-zero by 2050.

Baker, who has been vocal in his concern about a lack of affordable housing and the housing shortage in general, did not comment about the new proposal to allow gas bans in 10 communities. “The governor will carefully review any legislation that reaches his desk,” said spokeswoman Anisha Chakrabarti.

But activists worry that this issue could once again draw a veto.

“We can’t keep doing that — it doesn’t work for the health of the people or the planet,” said Karl Müller, a climate organizer with UU Mass Action and Mass Power Forward, who on Thursday and Friday was among a small group of activists singing and calling for the climate action at the State House.

“The stakes are high, and people need to see progress,” Müller said. “It’s an incredibly dark time to be an advocate, and to be caring about the planet and about justice. We need to keep moving forward.”

Read the full article in The Boston Globe here.