Your winter heating bill probably makes you wince a little. In the city of Boise, Idaho, though, a large section of downtown is warmed with water that has been heated in the ground already, and has been that way, in various forms, since the 1890s. According to a 2017 paper, "The Nation's Oldest and Largest Geothermal District Heating System," by Leland Mink, published in the journal GRC Transactions, drilling for hot water there began in the late 1890s. Boise now has four geothermal heating systems, which together heat an estimated 7.4 million square feet. The figures Mink cited are as of 2017, so take them with a grain of salt. The details behind the numbers are more interesting.
A 19th-century system with real staying power
The city's early geothermal push moved quickly. According to Mink, crews hit 175-degree water 404 feet underground in January of 1891. Homes on the system were paying "$2 to $3 dollars a month," while other residents in Boise were paying $7 to $8 a ton for coal. A huge indoor swimming pool, the Natatorium, opened in the city in 1892, and its pool was among the largest in the country.
