Based on the amount and duration of external temperature, degree day values are determined according to whether the selected equilibrium temperature is lower or higher than the air temperature. Degree day values are calculated according to the fluctuations in ambient temperature. It can be understood whether heating or cooling systems are necessary within the calculated periods. In this study, the meteorological data of Antalya region dating back many years and the temperature values suggested according to the cultivation periods of tomato in greenhouse environment have been used as material. The daily average temperature values recorded for many years have been compared with the equilibrium temperature values selected for the tomato plant thereby calculating the heating and cooling day values for each cultivation period. Tomato cultivation in greenhouses is carried out in 2 periods in the region in spring and autumn. At the end of these two periods, it was determined that the heating degree days in autumn were determined to be higher than that in spring. Whereas cooling degree days were determined to be greater for autumn cultivation in comparison with that of spring cultivation. Information regarding the energy consumption of an agricultural structure can be obtained beforehand via the ...