Why being in hot water in Idaho is actually a good thing

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Almost 500 buildings in the province’s capital get heat from clean, renewable sources deep in the ground.

It’s very easy to get into Boise’s hot water. After all, it’s Idaho, a state filled with hundreds of hot springs.

The city has used warm water in its natural environment to create a geothermal system that operates the largest local government in the country.

Nearly 500 Boise Business, Government Buildings, Houses, and Hospital and University Buildings; City Hall and YMCA. – Warmed by heat drawn directly from a hot water reservoir or aquifer below the ground. Idaho State University in Boise is the only US that uses geothermal heat. In winter, heat warms some sidewalks and raises the temperature of the hot tub to melt the snow.

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Renewable, reliable and relatively free of pollution, but geothermal heating is possible due to fault lines that expose groundwater to hot rocks and heat the water to about 170 degrees Fahrenheit, or about 77 degrees Celsius. The water is drawn from a well in a nearby hilly area into a closed loop network of pipes reaching the building, then returned to the aquifer to reheat.

In each building, geothermal heat is transferred to the water through adjacent pipes, dispersing the heat throughout the building.

“We pumped water, borrowed heat for the building, then reverted it back to the aquifer,” said Tina Riley, Geothermal Development Coordinator at Boise.

The number of buildings that heat up the city of Boise in this way has increased more than six times over the past 40 years, and has grown along the way. One of the consequences of the expansion is cleaner air. In 2024, city officials calculated that their carbon footprint is 6,500 tons a year, equivalent to removing 1,500 vehicles from the road each year.

“There’s a lot of demand for clean, affordable local energy,” Riley said. “This also has the energy independence.”

Boiseans began using this natural resource to heat the buildings in the 1890s. It gave birth to hundreds of thousands of gallons of piping hot water a day after drilling the well into the aquifer. The water-heated pools and baths of local swimming pools, the Victorian mansion belonging to the head of the Water Company, and hundreds of homes in the area that baptized the Boise Warm Springs Water district.

Things may have ended because it wasn’t due to the oil crisis of the 1970s.

“At that point, the Boise Warm Springs area had been thriving for almost 100 years,” Riley said. “That’s what we saw. Then we say, ‘Let’s do the same thing.’ ”

Today, Boise has four individually operated geothermal hydrothermal systems. One is run by the city, the other is run by the Boise Warm Springs area, and two more serve the Capitol and the U.S. Veterans Affairs buildings.

The city’s system operates as a utility funded by the sale of water rather than taxpayers. Riley said the heat price is roughly comparable to that of natural gas, depending on the efficiency of the building, but it is less expensive when used in parallel with a heat pump.

In the Boise Warm Springs Water area, engineer Scott Lewis said it is particularly cost-effective for warming an old Victorian home where geothermal heat had not been weathered.

He said that because it uses minimal electricity, it means all the stress on the power grid is less. The district costs $1,800 a month to power water pumps that provide heat to more than one million square feet of space. The expansion of the geothermal network is limited by what aquifers can offer, but Lewis said the district is trying to add 30 more homes to the network to meet demand.

“It’s actually very desirable, especially around the area,” he said. “We see that a lot of people are really environmentally conscious around here.”

The heating system attracted visitors from Iceland, Croatia and Australia, making Boise the destination.

“We were from all over the world,” Lewis said. “We love to let everyone know about our little geothermal system here.”