Over the years, they’ve been scoffed at as overly earnest activists or out-of-their-depth dilettantes.

At male-dominated energy conferences, they’ve been ignored, belittled as “gals,” and suffered through endless mansplaining in their areas of hard-fought expertise. Zeyneb Magavi, a 5-foot-1 engineer with a black belt in karate and a degree in physics, was once patted on the head and told she was “nice.” Her business partner, Audrey Schulman, a similarly diminutive novelist, has received condescending praise for “learning so much.”

“It can be exhausting trying to prove ourselves,” Magavi said.

They’re no longer so easily dismissed.

The duo of strong-willed Cambridge women, who joined forces over a common fear of how climate change would affect their children, recently had their once seemingly outlandish ideas for reducing carbon pollution adopted by the region’s largest utilities.

Last month, after years of prodding, state regulators approved a $16 million project that Magavi and Schulman proposed to demonstrate that there’s a financially viable, technically sound way to heat and cool the vast majority of the state’s homes and businesses without fossil fuels. The project uses linked heat pumps and subterranean pipes that can harness steady underground temperatures to heat and cool buildings.

That project, which will be installed by National Grid, follows the state’s approval of a similar geothermal project — also based on their ideas — proposed by Eversource, which plans to spend $10 million starting this year to connect about 100 homes and businesses in Framingham with a network of ground-source heat pumps.

If both projects work — heating and cooling air at reasonable costs — Magavi and Schulman hope the utilities will stop spending hundreds of millions of dollars a year replacing their aging system of gas pipes, and instead direct that money to installing geothermal energy throughout the region. Eventually, they believe, such emissions-free systems could replace the need for gas and oil in most homes.

The plan, Magavi and Schulman say, will also save state residents money in the long run. Every ratepayer dollar spent on investing in the utilities’ thousands of miles of gas pipes, which leak substantial amounts of methane that contributes disproportionately to global warming, will likely saddle future generations with unnecessary debt for what will largely become useless infrastructure as the state moves away from fossil fuels.

State law now requires emissions in Massachusetts to be reduced 50 percent below 1990 levels by the end of the decade and effectively eliminated by 2050. That means utilities must find new ways of heating and cooling buildings, which are among the largest sources of greenhouse gases. The sooner they stop investing in oil and gas, the more the utilities can spend on clean energy.

“Who wants to spend $500 million a year on gas mains that we won’t be using in the future?” said Schulman, citing the amount of money the utilities spent in 2020 on replacing their gas pipes. “We need the utilities to work with us, and innovate.”

Magavi and Schulman met more than a decade ago as neighbors in Cambridge, both anxious to do something about climate change. Magavi, who started out as an engineer designing torpedo simulators for a defense contractor and later worked on global health issues, began volunteering with Mothers Out Front, a local group of climate activists. Schulman, a writer who will soon have her sixth novel published, helped found an environmental nonprofit called the Home Energy Efficiency Team, or HEET, in an effort to make homes more energy efficient.

“It became clear that the scale of that effort was wrong, that individual action wasn’t going to be enough,” Schulman said of their early efforts at HEET.

Magavi eventually joined HEET as co-director, and they turned their attention to the thousands of gas leaks in Massachusetts spreading methane, a potent greenhouse gas.

That work led them to their first meeting, in 2016, with Bill Akley, president of gas operations at Eversource.

“We were asking them to work with us,” Magavi said. “They had no idea what they were getting into.”

Akley decided to meet with them after a series of protests about the gas leaks began creating significant “angst” and “hardship” for the company, he said.

“There was a contentious backdrop to that meeting,” he said.

But it quickly became clear that Magavi and Schulman weren’t there to throw rhetorical bombs or dump on the big, bad utility; they came with data and proposals about how they could collaborate.

Over the years, they had gained credibility by working with Eversource and other utilities to develop tools, such as what they called the FluxBar, to help their crews pinpoint the source of methane leaks and more accurately measure how gas was being released. They commissioned studies and spent time with workers in the field, demonstrating that they understood the often-thorny challenges of delivering energy to millions of people.

“Their passion for accelerating the clean energy transition, while considering practical solutions, are reasons why we’ve engaged and will continue to collaborate with HEET,” said Owen Brady-Traczyk, manager of non-pipeline alternatives at National Grid.

With more than a quarter of the state’s greenhouse gas emissions coming from commercial and residential buildings, Magavi and Schulman began pressing the utilities to think bigger. They estimated the companies are on track to spend more than $20 billion in ratepayer money on replacing about 5,000 miles of gas pipes, and that seemed to be a colossally bad idea, given the urgent needs of eliminating emissions.

“We wanted to find a way to reallocate that money,” Schulman said.

They looked at the possibility of the mass installation of air-source heat pumps, but they’re less efficient, as they must cool or heat air from fluctuating outdoor temperatures. So they proposed that the utilities consider building networks of heat pumps that would extract cool or hot air from the ground, where temperatures in New England are consistently about 55 degrees all year.

Such geothermal systems are in use elsewhere in Europe and the United States, such as those at Colorado Mesa University, where campus consultants say they’re saving about $1 million a year in energy costs. When a university building requires heat, a pump pulls warmth from the subterranean pipes; when it needs cooling, the pump releases warmth into the pipes.

What distinguishes their proposal from other geothermal projects is that it would be managed by utilities, which would use their legal right of way to drill holes — some as deep as 500 feet into the ground — and install water pipes that would connect via service lines and heat pumps to buildings. The utility could install the system block by block, starting where they need to replace aging gas pipes, and eventually link the geothermal network to neighborhoods, cities, and larger regions.,

The larger the network, the more efficient and reliable the system, and the lower the cost, they said. In some areas, especially rural parts of the region, such systems could be impractical, because buildings are too spread out to be linked together.

While the upfront costs for digging the holes, laying the pipe, and connecting the heat pumps will be expensive, they’ll be borne by all ratepayers. Customers individually will have to pay for the electricity to run their heat pumps, but they won’t have to pay for fuel.

“Ratepayers will ultimately have to cover the construction costs, but their overall energy bills are likely to be the same or lower than they pay for gas today,” Schulman said.

Over the past few years, they’ve evangelized about the promise of networked geothermal systems around the country, and now their ideas are gaining traction elsewhere, too.

Their proposed “GeoGrid” is being considered by utilities in New York, Oregon, Colorado, Connecticut, and beyond. Attorney General Maura Healey’s office has devoted $4 million from a settlement with Columbia Gas, which in 2018 experienced a series of explosions in its gas pipelines in the Merrimack Valley, to build a geothermal demonstration project there.

“What Zeyneb and Audrey have accomplished so far is truly extraordinary,” said Jack Spengler, a professor of environmental health at the Harvard T.H. Chan School of Public Health. “They have been able to motivate a conservative industry to reimagine its purpose.”

Some, however, have taken issue with their approach.

Bob Wyman, an energy consultant, said that while he agrees that geothermal systems are the best way to replace fossil fuels in heating homes and businesses, he would prefer more competition among those who want a part of the new business; utilities, he believes, should not control the system.

“We should not simply convert regulated gas monopolies into regulated geothermal grid monopolies,” he said.

Magavi and Schulman said they welcome competition, but they believe there are significant benefits in working with the utilities.

“The gas utilities’ existing workforce, rights of way, financing, customers, billing, and more, make possible the speed and scale of energy transition our state law requires,” Magavi said.

At Eversource, which has been receiving requests for geothermal projects from interested communities around the state, officials said that if their demonstration project in Framingham succeeds, they hope to move quickly to replicate it elsewhere.

“We’re very excited about how big and broad the scale could be,” Akley said. “We want to take this as far as it can go. We’re all in.”

David Abel can be reached at david.abel@globe.com. Follow him on Twitter @davabel.

Work at Boston Globe Media