Geothermal energy is heat contained in rock and fluids in the Earth’s crust. In most areas, this heat reaches the surface in a very diffuse state. However, relatively shallow geothermal resources exist in each of the Northwest states. There are two main applications of geothermal energy: direct use and geothermal heat pumps, also known as GeoExchange, ground-source, or water-source heat pumps.

Heat Pumps


Geothermal heat pumps (GHP) use the earth, groundwater or even surface water as a heat source in winter and heat sink in summer. Using resource temperatures of 40-100°F, the heat pump transfers heat from the soil or water to the house in winter, and from the house to the soil or water in summer.

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Direct Use


Direct use taps the heat of the water for such needs as space heating of buildings, greenhouses and aquaculture. Direct use projects usually use temperatures between 100-300°F. For electrical generation, the water source needs to be at least 270° F.

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