Built-in solar storage is an alternative to the traditional solar collectors. This paper explores the possibility of utilizing such solar stores for frost prevention in greenhouses. In the study, two identical NE-SW orientated greenhouses with 50 m(2) ground area were erected. The total ground area and volume of the water stores used in the solar greenhouse were about 64 and 5.4% of the total ground area and volume of the greenhouse. The short-term results showed that at times when the air temperature in the control greenhouse dropped below 0 degrees C, it was about 3.5 degrees C in the solar greenhouse, and sometimes this difference was more than 4.5 degrees C. The average fraction of solar energy storage by the stores was 0.26 fora four day period.