The first geothermal power plant was invented in 1904 by Prince Piero Ginori Conti. This system used steam to generate electric power.
It wasn't until 1922 that the first geothermal plant was built in the United States with a capacity of 250 kilowatts. Its output was little and was later closed due to technical problems. Later in 1946, a ground-source heat pump was built at the Commonwealth Building in Oregon. The first large-scale geothermal plant, with an output of 11 megawatts, was built in San Francisco in 1960s. Geothermal heat pumps gained popularity in the 1980s following the oil crisis in 1973. Since then, geothermal power has continued to develop with the increasing need to reduce cooling and heating costs.