Heat can be obtained from the Earth in various ways from deeper sources for larger networks and heat for power generation—combinations are also possible. Geothermal energy is classified as a renewable resource because the tapped heat from an active reservoir is continuously restored by natural heat production, conduction, and convection from surrounding hotter regions, and the extracted geothermal fluids are replenished by natural recharge and by injection of the depleted (cooled) fluids. Geothermal fields are typically operated at production rates that cause local declines in pressure and/or in temperature within the reservoir over the economic lifetime of the installed facilities. These cooler and lower‐pressure zones are subsequently recharged and renewed from surrounding regions when extraction ceases.