Boise plans to tap its geothermal network to heat 300 affordable homes

Boise already knows how to tap the carbon-free heat beneath our feet. The city operates the country’s largest geothermal heating system, which pipes naturally warmed, 177-degree-Fahrenheit water from underground to about 100 buildings — including the Idaho State Capitol. 

Last week, semiconductor multinational Micron Technology gave Boise $2.5 million to build on that expertise. The cash fills a funding gap to extend the geothermal system to a planned affordable housing development with more than 300 units. In total, the project price tag is about $140 million, according to the city. 

“Boise has been Micron’s headquarters for 48 years, and investing in this community means investing in the people who call it home,” April Arnzen, executive vice president and chief people officer at Micron and president of its philanthropic arm, the Micron Foundation, said in a statement. 

In February, the Bloomberg Philanthropies Mayors Challenge awarded Boise $1 million to upgrade its geothermal system for affordable housing, as well as to explore a new use for the network: Some early-stage technologies exist that could potentially harness the hot water from Boise’s system to provide cooling, according to Maria Ortega, the city’s communications senior manager.

The clean-heat expansion will help Boise get closer to its goal of becoming carbon-neutral by 2050. Already, the city’s geothermal network cuts thousands of tons of carbon emissions every year, the equivalent of taking more than 2,000 gas-powered cars off the road. 

Geothermal networks like Boise’s are gaining traction across the country, with 33 scattered projects planned, in construction, or completed, according to the nonprofit Building Decarbonization Coalition. These systems, which rely on bore holes, can form a part of thermal energy networks that move heat among buildings and serve as a climate-compatible business model for gas utilities. 

Denver is planning to harvest heat from the earth and sewage to keep downtown buildings comfy. The tiny rural town of Enfield, North Carolina, secured seed funding earlier this year for a geothermal network to lower residents’ energy costs. And in Framingham, Massachusetts, about 140 customers are the first in the U.S. to be heated and cooled with a geothermal network owned by a gas and electric utility, Eversource Energy. Last December, that project got an $8.6 million federal grant to double in size.

Back in Boise, the Housing Land Trust Program has partnered with J. Fisher Cos. to develop the affordable multifamily housing project in the Lusk District. It’s expected to break ground in spring 2027 and be ready for residents in 2028. Because renewable geothermal energy itself is free, the network could save residents up to 80% on utility bills, according to the city. 

“Building more homes that Boiseans can afford takes partners who are willing to roll up their sleeves and invest in solutions,” Mayor Lauren McLean said. ​“Thanks to Micron’s investment, we are one step closer to bringing clean geothermal heat to hundreds of affordable homes in Boise.”