AMERICAN ENERGY SOURCES:

The concept of tapping the earth's heat has been around for centuries, and modern heat-pump technologies have existed for decades. Yet relatively few buildings in the United States have taken this approach to date, owing to high upfront costs, the complexities of digging into the ground, and the fact that geothermal technology remains obscure to many people. Around 50,000 geothermal heat pumps a year are now installed in the United States, representing a tiny fraction of the country's many millions of buildings.

"Geothermal resources are literally beneath our feet and hidden in the ground," Alexis McKittrick, a program manager at the U.S. Department of Energy's Geothermal Technologies Office, says later by email. ​"The public is generally unaware that geothermal resources exist and could be used for a wide array of applications."

That's starting to change as city councils and state governments in New York and nationwide begin to restrict planet-warming emissions and limit fossil-fuel use in buildings, which account for 13 percent of annual U.S. emissions. A raft of new federal incentives, including through 2022's Inflation Reduction Act, is also expected to make systems more affordable and increase overall installations, McKittrick said.

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