Can Geothermal Power Play a Key Role in the Energy Transition? Aided by advances in deep-drilling technology for fracking, engineers are developing new methods of tapping into the earth’s limitless underground supplies of heat and steam. But the costs of accessing deep geothermal energy are high, and initial government support will be crucial. A river of hot water flows some 3,000 feet beneath Boise, Idaho. And since 1983 the city has been using that water to directly heat homes, businesses, and institutions, including the four floors of city hall — all told, about a third of the downtown. It’s the largest geothermal heating system in the country.