Boise officials want to increase geothermal heating

November 26, 2021 GMT

BOISE, Idaho (AP) — The city of Boise is looking to expand its geothermal heating system by 40% as part of a goal to become carbon neutral by 2050.

The city pumps 250 gallons (946 liters) of geothermal water to 96 buildings through 21 miles of pipes (34 kilometers). The water has a temperature of 177 degrees Fahrenheit (80 degrees centigrade).

City officials said that the geothermal heat supplies about 2% of the city’s energy resources.

“Geothermal really provides that clean energy alternative,” said Climate Action Manager Steve Hubble, the Idaho Statesman reported Thursday.

The heated water comes from a river of geothermally heated water flowing under the nearby foothills. Experts say the water is heated by the Idaho Batholith, a massive igneous intrusion of granite producing heat through decay of isotopes like uranium, thorium, and potassium.

Boise Geothermal Program Manager Jon Gunnerson said a large fault line runs through the Boise foothills and helps bring the water near the surface. The hot water is pumped from city-owned wells in the foothills to buildings, and then returned to the aquifer.


City officials said they want to expand the use of the geothermal water by 5 million gallons (18.9 million liters) a year until reaching 355 million gallons (1.6 billion liters).

Gunnerson said anyone interested in switching to geothermal should contact his office. The city says the rate is competitive with natural gas prices.

“It’s kind of one of those hometown assets that (Boiseans are) really proud of,” Hubble said.

Boise residents have been using geothermal heat for about 130 years, and there are four geothermal networks in the city. Besides the city’s system, there’s a private system heating homes on Warm Springs Avenue, another the state owns that heats the Statehouse and other state-owned buildings, and a fourth operated by the U.S. Department of Veterans Affairs for its facilities in Boise.

Besides the Statehouse, City Hall and the Ada County Courthouse are also heated with geothermal water.

Eleven buildings at Boise State University are heated with the geothermal water as well. That’s the farthest point from the wells in the city’s system.

The water cools the farther it gets from the wells, officials said, limiting how far the hot water can be used.

“It’s really going to be the downtown core and within an arm’s reach in each direction,” Gunnerson said.

Boise spokesman Colin Hickman said wells have plenty of capacity, and there are no plans for new production wells.