A prototype of a plastic house ventilation system driven by electricity provided from photovoltaic (PV) generators was assembled. The ventilator opened or shut the side windows of the plastic house according to the temperature in the plastic house. The model system was driven by electricity only from PV during two experimental terms: from 18 September 2000 (9/18) to 10/16 and from 11/5 to 12/3. According to energy balance analysis, more energy was consumed when the side windows were completely open or shut than at any other time. Moreover, the standby power consumption when the side windows were held in the open position was nearly double that at the shut position. The minimal capacities of the PV modules and the batteries to drive the model system stably under the weather conditions during the experimental terms were determined. The values were 18.6W and 15.6Ah during 9/18-10/16, and the values were 17.2W and 11.4Ah during 11/5-12/3, respectively.