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Idaho uses geothermal water for heating buildings, generating electricity, growing plants and water life, and for recreation. Geothermal power plants are an excellent renewable and alternative energy because they are a long-term, secure power source that has minimal fuel supply costs once in production; and because they provide base load renewable power 24 hours per day 7 days a week.

Idaho is a prime candidate for additional geothermal energy development in the future because the State has vast, untapped and underused geothermal resources with an estimated 800 megawatts MW of near-term geothermal-powered generation potential. Boise is home to the oldest geothermal district heating system in America and the Idaho State Capital Building is the only state capital building in the U.S. that is heated with geothermal energy. Idaho is also home to one of the first geothermal power plants in the Pacific Northwest, the U.S. Geothermal Raft River Facility, which started generation in January 2008.

The Idaho Governor’s Office of Energy and Mineral Resources actively supports the use of geothermal energy for power generation, heating, business ventures, research, and recreation.


Idaho has a rich history of geothermal use beginning with Native Americans who congregated at hot springs as indicated by artifacts and petroglyphs on nearby rocks. Hot springs were also used by settlers, miners and trappers by the mid 1800’s. In 1892, the nation’s first district heating system was birthed in Boise (Figure 1). The system is still in use and has been joined by three more district heating systems in the Boise area.

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The Natatorium was a landmark in Boise that used geothermal water for recreation for over 40 years. The Natatorium was part of the Warm Springs Water District which has been in operation since 1892. Photo credit: Idaho State Historical Society (73-2.52)


At least 10 geothermal resorts and spas have been around in Idaho since the late 1800’s and early 1900’s. In 1930, Edward’s Greenhouses became the first commercial greenhouse operation in the United States to use geothermal water to grow plants. Several other geothermal greenhouse businesses emerged in southern Idaho over the next 50 years.

In 1973, Leo Ray became the first person to use geothermal water to raise catfish in Idaho. Currently, 12 aquaculture businesses are operating in Idaho raising tilapia, catfish, sturgeon, ornamental fish, alligators and marine reefs with geothermal water.

In the 1970’s, the nation’s first energy crisis stimulated the development of five district heating systems in Boise and Twin Falls, and a geothermal power plant pilot project in the Raft River area. In the 1980’s, heavy pumpage led to declining water levels in some places, which prompted the Idaho Department of Water Resources to restrict additional geothermal developments in Ada and Twin Falls Counties. Idaho’s geothermal development slowed in the 1990’s, except for some home heating projects in Boise and Owyhee Counties.

In the early 2000’s, geothermal activity in Idaho started picking up. An agreement between several geothermal users in Ada County allowed the City of Boise to expand its customer base. U.S. Geothermal, Inc., purchased the Raft River site, completed development for a new power plant and began generating electricity in 2008. The BLM auctioned five parcels (8,904 acres) in Idaho for geothermal power exploration in July 2007; the total paid for the lease bonuses was $5.7 million.

Geothermal development is a slow, tedious and expensive process. But, since Idaho has proven resources capable of power and direct use applications, there are plans, dreams and hopes that additional utilization of geothermal will occur in the state in the near future.

Detailed History

For more history on geothermal energy in Idaho, please CLICK below.

Direct Use means that the heat energy from geothermal water is utilized through either direct contact or through heat exchange for a specific process. Examples include:

  1. heat exchangers extract thermal energy which is transferred to air and used to heat homes, businesses, and public buildings,
  2. hot water flows through radiators in a home and heats the rooms,
  3. geothermal water is put directly into raceways and fish are raised,
  4. hot water goes into a pool for swimming, and
  5. geothermal circulates through pipes in a greenhouse and heat radiates for the plants.

Direct Use applications in Idaho use water with temperatures ranging from 90° F to 175° F. Idaho entrepreneurs have found many creative ways to use geothermal water directly for financial success, such as district heating, plant propagation, aquaculture, and aquaponics.

Geothermal Aquaculture is big business in Idaho, where catfish, tilapia, ornamental fish, coral, aquatic plants, and alligators are all being raised. People have used this natural hot water in Idaho since 1973 for aquaculture businesses and research (see Map 1). Leo Ray of Hagerman was probably the first person in Idaho to use geothermal water to raise aquatic life. Catfish, alligators and tilapia (the most commonly raised aquaculture product in Idaho) are raised in 95° F water. Mr. Ray’s alligators have multiple uses as food, to eliminate byproducts from his processing operations, and as hides for leather goods.

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Map 1. Geothermal Aquaculture Operations and Associated Products in Southern Idaho

Geothermal Greenhouses are also viable business ventures in Idaho, where lilies, roses, poinsettias, cut flowers, potted plants, vegetables for market, and flower and vegetable bedding plants are grown year-round and sold in various markets across the country (see Map 2). Most geothermal greenhouses raise plants for wholesale, although a few are open to the public. Geothermal energy is extracted either through a forced air system or by direct circulation around the plants. Some greenhouse owners also use geothermal water for irrigation. Water temperatures in Idaho greenhouses heated by geothermal are generally in the range of 115° to 120° F.

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Map 2. Geothermal Greenhouse Operations in Southern Idaho
Idaho has over 900 wells and springs with water temperatures greater than 90° F; however, only about 20% of these are currently being used for thermal purposes. There are many opportunities left in the state for additional geothermal ventures. As Idaho businesses have demonstrated already, the direct uses of geothermal energy can be important revenue generators for local communities.

Geothermal water heats homes and buildings throughout Idaho, ranging from the Idaho State Capitol to mobile homes. A well can supply heat for an individual home (see map 3) or multiple buildings connected to a system of distribution lines resulting in a district heating system.

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Map 3. Geothermal Non-District or Residential Heating in Idaho.
There are two methods to extract heat from geothermal water. Method 1, the open-loop system, works as follows:

  1. A well is drilled into a geothermal aquifer.
  2. Geothermal water is withdrawn from the well.
  3. The water circulates through the home.
  4. Heat radiates from the distribution system (pipes in the floors or radiators) and warms the home.
  5. Spent water is either reinjected into the aquifer or discharged away from the house.

Areas near Hagerman Valley, Boise, Garden Valley, and Near Lakey Hot Springs used this system.

Method 2, the closed-loop system, uses this approach:

  1. A well is drilled into a geothermal aquifer.
  2. Carbon steel or copper piping is placed in the well bore and down into the water (this is known as the downhole heat exchanger).
  3. Piping connected to the downhole heat exchange is run into the house, under the floorboards or in radiators.
  4. The piping is filled with water.
  5. The ends of the pipe are joined together forming a closed loop.
  6. The water circulates through the piping, usually with the aid of an in-line pump. As the water inside the loop passes through the piping in the well, the heat from the surrounding water is transferred into the closed loop. As the water circulates through the piping in the home, the heat is released.

Residences near Crouch and in northwest Owyhee County near Givens Hot Springs utilize the closed-loop method.

District heating systems deliver steam or hot water to multiple buildings for climate control. There are six geothermal district heating systems in Idaho (see map).

  • Boise Warm Springs Water District (BWSWD)
  • City of Boise
  • State of Idaho – Capitol Mall Complex (Boise)
  • Veterans Administration (Boise)
  • College of Southern Idaho (Twin Falls)
  • Kanaka Rapids Ranch (north of Buhl)
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Map 4. Geothermal Heating Districts in Idaho
The four systems in the Boise area withdraw approximately 775 million gallons of geothermal water per year to heat over 200 homes, and about 85 government buildings and businesses, and then reinject about 70 percent of it back into the aquifer. Each system functions independently of the other systems, and operates with its own wells and unique distribution system. BWSWD, the oldest system, began operating in the late 1890’s. The other three Boise systems developed in the 1980’s, in response to the first Energy Crisis of the late 1970’s. The supply water temperatures for these Boise systems range from 155° to 175° F. The wells range in total depth from 400 to over 3,100 feet.

Two district heating systems in Twin Falls County use water that is considerably cooler. The College of Southern Idaho (CSI) in Twin Falls City converted most of its heating system to geothermal after the late 1970’s energy crisis. The college uses two deep wells (1,480 and 2,200 feet) to heat 12 campus buildings. The water temperature is only about 101° F. In addition to heat exchanger technology, the college employs heat pumps to extract as much thermal energy as possible from the water. About 20 miles to the northwest, the Kanaka Rapids Ranch uses two wells to supply geothermal water to a low-density neighborhood along the Snake River. The water from these wells is a few degrees cooler than the water at CSI. At least 10 other areas in Idaho have been studied for potential district heating operations.

Idaho has an abundant near-term geothermal resource potential with estimates of more than 800 megawatts (MW) of geothermal-powered generation potentially available. Geothermal power generation is appealing because it provides baseload renewable power 24 hours per day 7 days a week and is a long-term, secure energy source with minimal fuel supply costs once in production. Having low environmental impacts with little or no greenhouse gas emissions or effects on wildlife and viewscape using very little land compared to conventional energy resources, makes geothermal power generation an appealing alternative.

However, like oil and gas discovery, geothermal reservoirs require high risk drilling to define the energy capacity of each reservoir able to meet the requirements of power production and district heating. Combined with the upfront high capital costs, geothermal power generation does present some challenges. These challenges are offset by the low (or zero) fuel cost and minimal ongoing costs that allow for the recovery of initial capital costs that over time make geothermal energy an economically viable renewable energy. The discovery challenge can be offset by collaboration and research done by organizations such as CAES, the Center for Advanced Energy Studies, a research and education partnership between Idaho’s major universities and the Idaho National Laboratory. The Raft River Geothermal site is a success story of the partnership between research and the private sector.

The Raft River geothermal site in Cassia County of south central Idaho has a couple “First” distinctions in its history of electrical power generation. In the early 1980’s, this Department of Energy demonstration project was the first binary plant in the U.S. to produce electricity. At that time, the economic conditions were not favorable for using the plant, so it was discontinued. In 2002, U.S. Geothermal Inc., purchased the facility and began the process of installing a new power plant. In early 2008, the Raft River site became the first commercial geothermal power plant in the Pacific Northwest. U.S. Geothermal Inc. has a 20 year contract with Idaho Power to supply 10 MW of electricity under this Phase 1 project. U.S. Geothermal Inc. believes that its 8.2 square mile lease position has a production capacity of 110 MW. Combined with the Neal Hot Springs Geothermal power plant facility near Vale, Oregon, Idaho Power provides about 35 MW of clean energy to Idaho customers, enough energy to power about 35,000 homes.

Idaho welcomes geothermal exploration and power development, and the Idaho Governor’s Office of Energy and Mineral Resources is available to facilitate both.

The wealth of geothermal resources in Idaho provides residents and visitors with an abundance of opportunities to enjoy a relaxing dip in the state’s hot springs and pools. Native Americans, gold miners, Oregon Trail immigrants, river runners, and local residents have all taken advantage of easy accessibility to the many hot springs in Idaho. Recreational use of these geothermal resources ranges from relaxing in small hot pools along rivers and roads, to taking a grueling backpack trip in search of the “perfect soak,” to visiting a developed commercial resort for swimming, soaking, and just plain taking it easy.

Most of the geothermal recreation areas, both undeveloped springs and developed resorts and spas, are found in the central part of the state, and across southern Idaho south of the snake river. The geothermal springs in the center of the state often occur in rugged mountain settings and are associated with the Idaho Batholith, a huge granite formation that contains faults and fractures which provide conduits for hot fluid movement to the land surface, U.S. Forest Service, Bureau of Land management, ect.

Non-commercial, or undeveloped, hot springs are common on private and on the public lands of Idaho. Several books and websites are available for those interested in finding out more about these undeveloped hot springs (see the lists at the bottom of the page).

The map below shows the location of geothermal springs in Idaho with surface water temperatures from 86° to 199° F.

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Map 5. Geothermal Recreational Pools in Southern Idaho

Commercial/Developed Resorts and Pools

The commercial value of geothermal waters in Idaho was discovered in the late 1800’s. Development of a geothermal area was often the result of the location being on a main thoroughfare. Local residents and hopeful prospectors on their way to the gold fields were the customers for some of the commercial sites in southern and central Idaho. Access to the railroads was also a draw for commercial hot springs, sometimes causing the thermal waters to become a destination spot.





District Heating

Power Generation

Heat Pumps and Other Geothermal Development


National Sites