California dominates geothermal energy production in the United States, generating about 66.6% of all U.S. geothermal electricity. Nevada comes in second with a rapidly growing portfolio of plants, and a handful of other western states round out the top producers. Nearly all commercial geothermal power in the country comes from a narrow band of geologically active land stretching from the southern California desert to the volcanic regions of the Pacific Northwest.
California Produces Two-Thirds of U.S. Geothermal Power
California’s lead isn’t close. The state accounts for roughly two-thirds of all geothermal electricity generated nationwide, and geothermal supplies about 5.1% of California’s total electricity mix. The centerpiece is The Geysers, a massive geothermal complex spread across 45 square miles in the Mayacamas Mountains north of San Francisco. Straddling Lake, Mendocino, and Sonoma counties, The Geysers produces about 835 megawatts of electricity, making it the largest geothermal field in the world. That power flows to communities across Sonoma, Mendocino, Lake, Marin, and Napa counties.
Beyond The Geysers, California operates significant geothermal plants in the Imperial Valley near the Salton Sea, where underground temperatures are extremely high and the resource base is enormous. These southern California facilities add hundreds of additional megawatts to the state’s total.
Nevada Is the Second-Largest Producer
Nevada has 28 operating and authorized geothermal power plants with federal interest, combining for a total authorized generating capability of over 950 megawatts, according to the Bureau of Land Management. Many of these plants are scattered across the northern and central parts of the state, tapping into hot water reservoirs along fault lines in the desert basin landscape. While Nevada’s raw megawatt capacity is substantial, its actual annual generation still trails California’s because not all authorized capacity runs at full output year-round.
What makes Nevada notable is the sheer number of individual sites. Rather than one dominant complex like The Geysers, geothermal development here is distributed across dozens of smaller projects, each exploiting a different hot spring system or fault zone. This distributed model has made Nevada a testing ground for newer exploration and drilling techniques.
Why the Western U.S. Has Almost All the Action
Geothermal power plants need two things underground: heat and a way for hot water to reach the surface. The western United States has both, thanks largely to the Basin and Range province, a vast stretch of land running from Nevada through parts of Utah, Oregon, Idaho, and into California. This region hosts a large fraction of the high-temperature geothermal systems in the country.
The Basin and Range is heavily faulted, meaning the earth’s crust has cracked and shifted extensively over millions of years. These fault zones act as natural plumbing, creating permeable pathways that allow groundwater to circulate deep underground, absorb heat from hot rock, and rise back toward the surface. There’s a strong correlation between geologically recent faulting and the presence of geothermal systems. Where faults are old and sealed up by mineral deposits, hot water can’t flow freely enough to be useful.
Unlike volcanic geothermal systems (such as those in Hawaii or parts of the Cascades), most Basin and Range systems don’t rely on magma chambers for their heat. Instead, they depend on the natural temperature increase that comes with depth, combined with groundwater circulating through fractured rock. This “extensional” style of geothermal system can only function within a relatively narrow range of underground permeability. Too tight and water can’t flow; too open and it disperses without concentrating heat.
Geothermal Heating Beyond Electricity
Geothermal energy in the U.S. isn’t limited to power plants. Several communities use hot underground water directly for heating buildings, a practice called district heating. Boise, Idaho, is home to the largest municipally operated geothermal heating utility in the country. The system traces its roots to the 1890s, when a local businessman first piped hot water from nearby springs. Today, more than 20 miles of pipeline warm over six million square feet of building space throughout the city.
Klamath Falls, Oregon, runs another well-established geothermal district heating system. The city began tapping geothermal heat in the early 1990s, and the network now serves 23 commercial, nonprofit, and government facilities. Smaller direct-use systems operate in other western towns, heating greenhouses, fish farms, and spa resorts.
Other Producing States
After California and Nevada, the remaining geothermal electricity producers are Utah, Hawaii, Oregon, Idaho, and New Mexico. Each contributes a much smaller share of total U.S. output. Utah and Oregon have a handful of operating plants, while Hawaii taps volcanic heat on the Big Island. Idaho’s geothermal profile leans more toward direct heating than electricity, though some power generation exists. Collectively, these states produce the remaining third of U.S. geothermal electricity that California doesn’t cover.
Enhanced Geothermal Could Change the Map
The geographic concentration of geothermal power in the West may not be permanent. A technology called enhanced geothermal systems (EGS) aims to create artificial reservoirs by fracturing hot, dry rock underground and injecting water to extract heat. This approach could theoretically work almost anywhere, not just where natural hot water systems already exist.
The most advanced test site is Utah FORGE, a Department of Energy project in central Utah. In 2024, the FORGE team confirmed a successful connection between two wells through a fracture network created by hydraulic stimulation, demonstrating that engineered reservoirs can transfer heat at a commercial scale. A Department of Energy analysis estimates that EGS technology could eventually provide 90 gigawatts of geothermal generating capacity nationwide, enough to power the equivalent of up to 65 million homes. For context, the entire current U.S. geothermal fleet produces only a few gigawatts. If EGS scales up, states across the Midwest, South, and East Coast could join the geothermal map for the first time.