A photovoltaic thermal forced circulation water heater has been modeled and simulated based on meteorological condition of Malaysia. The typical weather year file containing the weather parameters for Kuala Lumpur is used to simulate the system. Collector area is an important factor to achieve an adequate performance of solar water heater. In this study the effect of unglazed collector area on performance of the system has been investigated. The results of simulation study indicates that increasing collector area from 1m 2 to 10 m 2 results in an increase in useful heat gain, electrical power output, water temperature and an decrease in auxiliary heating rate. However, when collector area is greater than 7 m 2 , these improvements are small. Therefore it can be concluded that, increasing of collector area from 7m 2 to 10 m 2 has no significant effect on performance of the water heater. Furthermore increasing of heat gain for this range of collector area is negligible.
