3. PacifiCorp, 604,007 MWh/year
PacifiCorp, a unit of MidAmerican Energy Holdings, operates a large generation portfolio that includes solar energy, wind power and the 34 MW Blundell geothermal facility in Utah. Blundell uses a "flash" geothermal energy extraction process in which steam and brine from production wells are separated in centrifugal wellhead separators. Pipes channel the steam into a turbine that spins the generator to produce electricity. The process releases no greenhouse gases or other harmful emissions.