In hot water: Boise’s unique geothermal system heats Statehouse, City Hall, more


In several Inside Idaho editions, we dug deep into the ground of Idaho – uncovering the state’s gem and the gold mining era.

But did you know there’s another resource located deep below our earth’s surface that’s still used today?

Idaho’s Capitol Building was the first in the United States heated by hot water. The water is tapped and pumped from a source 3,000 feet underground. It’s a natural form of energy called geothermal and it’s one that’s been used in Boise for over a century.

The water, which is pumped into buildings, is heated by the rocks and fluids found thousands of feet underground – as far down to the earth’s hot molten rock.

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Resource used today

Boise City Hall summer
Boise City Hall. Photo: Don Day/BoiseDev

The state capitol building isn’t the only thing heated by geothermal energy. In Boise, there are over 20 miles of pipeline that heat over 6 million square feet.

According to the city’s website, Boise has the largest geothermal heating utility in the country – delivering 177° water to over 6 million square feet of building space.

“From heating buildings to sidewalk snowmelt and warming recreational pools, the City of Boise’s geothermal heating utility is innovative, renewable – and sustainable to the core,” the city’s website notes.

JUMP, Boise State’s Admin Building, and City Hall are just a few other buildings heated by geothermal energy.

Geothermal history

Moore-Cunningham House, 1109 Warm Springs Avenue. Photo: Library of Congress

Geothermal energy has been used to heat Boise buildings and homes since the 1890s. The first houses in Boise to ever be heated by geothermal energy were on Warm Springs Ave. when natural hot water from east of Table Rock was pumped into the large Victorian-style mansions.

The Moore Cunningham House wasthe first home in America to be heated with natural hot water.

“The combination of stately homes and geothermal heat makes this area one of Boise’s most historically significant local districts, as well as one of the most unique in the western states,” the city’s website

The original Natatorium, also located on Warm Springs Ave, was also heated by geothermal energy.

As people began planting roots in the city, more and more homes used this form of energy to heat their homes. It cost between $2-$3 per month.

In 1983, the City of Boise started the Geothermal Heat system. Today, it’s the largest, municipally-operated system in the country, heating over 90 buildings throughout downtown Boise.

Boise’s Geothermal system.
Anna Daly - BoiseDev Reporter
Anna Daly is a reporter for BoiseDev. She's an Emmy-winning journalist, and a professor at the College of Western Idaho. Contact her at

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