10,000 years ago - American Paleo-Indians in North America, used water from hot springs for cooking, bathing and cleaning.
1827 - The first industrial use of geothermal energy began near Pisa, Italy. Steam coming from natural vents (and from drilled holes) was used to extract boric acid from the hot pools that are now known as the Larderello fields.
1892 - The first district heating system in Idaho was powered directly by geothermal energy and later used in Oregon in 1900.
1904 - Prince Piero Ginori Conti tested the first geothermal power generator. It successfully lit four light bulbs.
1911 - The world's first commercial geothermal power plant was built there. It was the world's only industrial producer of geothermal electricity until New Zealand built a plant in 1958. In 2012, it produced some 594 megawatts.1907 - The first known building in the world to utilize geothermal energy as its primary heat source was the Hot Lake Hotel in Union County, Oregon, whose construction was completed in 1907.
1922 - The first geothermal plant in US started in with a capacity of 250 kilowatts. It produced little output and due to technical glitch had to be shut down.
1946 - The first ground-source geothermal heat pump was installed at Commonwealth Building in Portland, Oregon.
1960’s - Pacific Gas and Electric began operation of first large scale geothermal power plant in San Francisco, producing 11 megawatts.
1973 - The oil crisis sparked many countries to look for renewable energy sources and by 1980’s geothermal heat pumps (GHP) started gaining popularity in order to reduce heating and cooling costs.
1997 - As effect of climate change started showing results, governments of various countries joined hands to fight against it, for which Kyoto Protocol was signed in Japan in, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it.
2019 - There are more than 60 geothermal power plants operating in US at 18 sites across the country. Geothermal power today supplies less than 1% of the world’s energy in 2009 needs but it is expected to supply 10-20% of world’s energy requirement by 2050. Geothermal power plants today are operating in about 20 countries, which are actively visited by earthquakes and volcanoes.