A first-of-its kind project is tapping energy beneath the ground to heat and cool homes

A small-yet-growing group are tapping into a network of underground energy to heat and cool their homes.

(CNN) — Eric Mauchan’s Cape Cod-style house in Framingham, Massachusetts, does not have central air conditioning. So when the summer heat bears down, his four window AC units, two dehumidifiers and fans that keep the 2,600-square-foot home cool push his electricity bill to roughly $200 a month.

In the depths of winter, the monthly cost of warming the home with gas soars to about $400. His wife, Jennifer, deploys a classic New England tactic to cut down on the energy bill: telling the family to add layers of clothing and blankets before she touches the thermostat.

“I am a stickler about the temperature, because I don’t want to pay the money to heat the house,” she told CNN. “So, if my 13-year-old son is cold, I’m like, ‘put on a sweatshirt, put on an extra pair of pants.’”

But all that is about to change, as the family joins a small-yet-growing group who are tapping into a network of underground energy to heat and cool their homes.

Massachusetts, like the rest of New England, still heavily relies on planet-warming fossil fuels for heating and cooling. But some energy companies are looking to an unlimited thermal energy source below their feet as a clean alternative.

The problem is, this option currently comes with a high up-front price tag, even with tax benefits factored in. Installing ground-source heat pumps alone, which do the work of converting underground energy into usable household heat, could cost tens of thousands of dollars. Additional costs could follow, depending on the house size, ductwork installation and other electrical service upgrades needed.

Over the long term, however, bills are expected to be much lower. Switching from gas hookups to networked geothermal heating could cut energy costs by 15 to 20%, Eversource estimates. It could also reduce the average residential customer’s carbon pollution in Massachusetts by up to 60%, utility estimates show.

When utility company Eversource announced it was building a geothermal network in Framingham — and offering no-cost retrofits to participating homeowners — the Mauchan family jumped at the chance. They would have otherwise needed to pay roughly $100,000 for home geothermal upgrades, Eric said.

Eversource has so far connected 37 homes and businesses in Framingham, including the fire station, into its shared geothermal loop.

The city now boasts the first shared geothermal network led by a gas utility in the nation, and it could be a model for the future of clean home heating and cooling. This winter will be the system’s first test.

How it works

The Earth is one big thermal battery. While the outside air temperature fluctuates with the weather, underground temperatures stay roughly 50 to 60 degrees. For most of the United States, temperatures are warmer underground in the winter and cooler in the summer. It’s a limitless renewable energy source that some experts say could help replace planet-warming fossil fuels.

To tap into Earth’s energy, Eversource drilled 88 boreholes about 600 feet below ground and installed an intricate system of horizontal and vertical underground pipes. The company runs a mixture of water and antifreeze through them.

During the winter, the liquid in the pipes is warmed by the relative heat underground, then carried up to a heat pump unit installed in the home. The heat pump concentrates the warmth and pumps it through the home’s ductwork to keep residents warm and cozy.

The process is reversed in the summer. Since the Earth’s temperature is cooler than the air inside the house, the heat pumps draw the warmth out of the house and into the ground.

It’s too early to know how much money switching to geothermal will save customers. Eversource needs at least one full heating cycle — this winter — to measure changes in customers’ bills. But Nikki Bruno, the vice president of clean technologies at Eversource, said she expects the geothermal system will reduce them.

“Cost is a huge driver,” she said. “We’re very sensitive to making sure that service is generally safe and reliable, but also cost-effective.”

Eversource will run the pilot system for two years, collecting data on energy use and costs, the system’s performance, and customer satisfaction. People will then have the option to either go back to the old gas system or stay on geothermal. The company also intends to transfer heat pump ownership to customers at no cost.

Experts said the project’s data will be important for the development of similar, future systems.

“The more data we get from utilities like Eversource, the better off we’re going to be so we can make informed decisions” about deploying more geothermal, Jeff Tester, professor of sustainable energy systems at Cornell University, told CNN.

Future of gas utilities

Eight states, including Massachusetts, have passed laws allowing public gas utilities to become “thermal utilities” — effectively allowing them to add geothermal systems in addition to gas.

Four more states — Illinois, Connecticut, Rhode Island and Maine – have introduced similar legislation that has yet to pass. Nearly 30 utility companies have expressed interest in the gas-to-geothermal business model, according to data from HEET, a Boston-based clean energy nonprofit that advised Eversource on the project.

“We are overheating everything around us,” Zeyneb Magavi, a scientist and co-executive director of HEET, told CNN. “The idea that we could build thermal networks as a simple infrastructure … and tap all of that excess thermal in the world stored around us, we have a win-win.”

Using networked geothermal technology for heating isn’t new in the US. Many college campuses such as Cornell and Princeton are heated with geothermal systems. The challenge is expanding it, Tester said.

“It’s definitely scalable, but it would take more work and more cooperation,” he said. “And we hope that will happen fast, because the benefits are long-term, and I think it could really pay off, moneywise.”

Tester also noted the geothermal network isn’t entirely free of fossil fuels. Eversource’s heat pumps are powered by the New England electricity grid, which still heavily relies on natural gas.

Back in the Mauchan household, they are optimistic about their years to come on geothermal — hopefully, with fewer layers this winter. Eric Mauchan said they are slowly getting rid of their AC units to prepare for geothermal cooling during the summer.

Eversource, which has a recent grant from Department of Energy and HEET, is already in talks to add more homes to the loop.

Jennifer Mauchan said her friends and neighbors are already asking her about how to get on it. “Everyone is envious about our situation,” she said, “asking when it is going to be expanded.”

The-CNN-Wire™ & © 2025 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.

Report a Typo