Ground-source heat pumps (GSHPs), also known as geothermal heat pumps (GHPs), are recognized to be outstanding heating, cooling and water heating systems, and have been used since 1998 in the Turkish market. Greenhouses also have important economical potential in Turkey's agricultural sector. In addition to solar energy gain, greenhouses should be heated during nights and cold days. In order to establish optimum growth conditions in greenhouses, renewable energy sources should be utilized as much as possible. It is expected that effective use of heat pumps with a suitable technology in the modem greenhouses will play a leading role in Turkey in the foreseeable future.