Facility horticulture generally uses fuel oil boilers for heating. Possible difficulty in continuing business due to soaring fuel oil prices. The objective is to reduce energy consumption using solar heat. Firstly, we measured the actual environment in the greenhouse. Secondly, the relationship between fruit quality and the environment was considered. Finally, conducted experiments to optimize the heat supply. High quality fruit was seen when average soil temperatures ranged from 24°C to 27°C. Soil temperature can be controlled by heater temperature and distance from the bed.
