The aim of this study is to determine the heating and cooling potential of the greenhouses in the Mediterranean climatic zone, with aquifer thermal energy storage (ATES) known as one of the underground thermal energy storage application systems (UTES). In recent years greenhouse production reached to 44.000 ha in Turkey (Abak et all 1995). For high yield and quality in greenhouse crops during the winter months, inside temperature should be maintained at the critical value that can change depending on the species grown in greenhouse. For instance, for tomatoes the critical inside temperature should be maintained not below 12-13 C in the greenhouse. Due to this information and also last 20 year’s climate data in Mediterranean Region a greenhouse needs approximately 150 kW heating load during 90 days in a year, 8 hours in a day (Abak et all.1995). To provide this heating load, 6L/m No 6 Fuel-Oil or 9kg/m coal must be consumed. The fossil fuel consumption leads to an economic burden in the operating cost, besides ashes and undesirable gas emissions from coal combustion are the biggest barriers of the greenhouses in the Mediterranean zone. Additionally, the cooling requirement of the greenhouses for early autumn and spring months in the Mediterranean Climate and the advantages provided after cooling applications will be calculated. For these purposes, two separate greenhouses, each having an area of 360 m, in the research area of the Horticulture Department Faculty of Agriculture have been selected. One of them was heated and cooled by ATES technique (Figure 1). In the second one conventional heating system was used and there was no cooling system. Tomato and eggplant plants were grown in the greenhouses. But only tomato’s results are presented in this paper. Consequently, these two different systems/greenhouses were compared in terms of economical, environmental and agricultural aspects. Figure 1: Basic concept of the system