There are two types of geothermal energy. The first involves digging deep underground, sometimes miles below the surface, into underground reservoirs to tap steam and very hot water that can be brought to the surface for electricity generation. Those opportunities are found typically near tectonic plate boundaries or volcanic hot spots. In the United States that means west of the Mississippi.

The kind of geothermal available in Massachusetts isn’t as hot, or as deep. Using geothermal energy to heat and cool a building involves taking advantage of the steady temperature below the ground’s surface, a year-round constant around 55 degrees. Pipes are buried underground, either in shallow horizontal or vertical loops often several hundred feet deep, with water and often antifreeze pumping through them. In winter, the warmed water flows to the surface and is transferred into a heat pump, which concentrates the heat and distributes it throughout the house. In summer, the process is reversed to cool us down.

Geothermal engineering designs can be quite complex, and one size does not fit all as challenges vary from project to project. But technologies continue to improve and knowledge of best practices advances with each blueprint.

Similar to nuclear energy, geothermal is relatively inexpensive per unit of energy produced once a system is operational. The biggest barrier to entry, however, remains upfront costs.

Consider Boston University’s state-of-the art geothermal system at its Duan Family Center for Computing & Data Sciences building, commonly known as the “Jenga building.” That contains 31 bore holes extending 1,500 feet underground, about twice as deep as the John Hancock is high. The building, which cost $305 million to construct, uses no fossil fuels to warm or cool it.

The geothermal system added less than 1 percent to the total construction cost but is expected to pay those costs back in less than a decade, according to Dennis Carlberg, BU’s chief sustainability officer.

For some schools with big endowments, building new facilities and investing in geothermal is a sound long-term investment. Still, expecting other institutions to follow BU’s lead is asking a lot, especially if their projects require retrofitting existing buildings.

To help overcome upfront costs, the governor and House are proposing legislation to allow gas companies to own the heat loops beneath large buildings at places like universities and hospitals, which is not currently permitted. If a building owner agrees to a partnership, the gas company could recoup costs through tariffs — rate structures, fees, and rules — designed for that specific customer. Utility customers who aren’t part of the geothermal project would not pay for it, but its existence could lower energy bills for nearby homeowners and renters, as large buildings converting to geothermal would decrease overall energy demands.

The governor touts her plan as a job creator for people working in the gas industry whose jobs could be threatened if natural gas usage declines.

Geothermal work is slowly ramping up in Massachusetts. Currently, about 20 state-owned buildings have converted or are converting to geothermal heating and cooling. Additionally, two dozen K-12 schools in Massachusetts are installing or have installed geothermal systems.

The clock is slowly ticking if building owners want to take advantage of federal tax breaks. Through President Joe Biden’s Inflation Reduction Act, many geothermal energy projects became eligible for investment tax credits. Trump’s “One, Big, Beautiful Bill” got rid of incentives for residential customers but preserved credits of up to 30 percent for commercial properties. Those phase out starting in 2033 and sunset after 2034, unless extended. That might seem like a long ways off, but complicated design projects take a long time.

“You gotta get going now,” said Dano Weisbord, chief sustainability officer at Tufts. He helped coordinate a project at Smith College to convert the 147-acre campus in Northampton entirely to geothermal energy for heating and cooling, which will take about seven years from concept to complete build out. “To get the economics right, you have to experiment with design parameters.” (Weisbord added that a 2033 deadline is plenty of time for less ambitious geothermal projects.)

The other challenge with any geothermal conversion lays within old buildings themselves. BU’s Jenga Building was a blank slate. But many of New England’s buildings are still warmed by steam heat delivered through old clunky radiators, a 19th-century technology. Ripping cast iron radiators out and replacing them with heat pumps and duct work would be cost prohibitive for many projects.

The University of Massachusetts Amherst is facing that challenge, said UMass professor Erin Baker, who researches mathematical modeling of energy decisions. She says for geothermal to make sense economically, policy makers may need to provide “some extra funding for the first movers, for the people that are initially doing it.”

Or large institutions just have to “bite the bullet” and retrofit the building, Baker said. “Then for decades, you have very low operating costs, you have very clean energy.”

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