This study was carried out to theoretically and experimentally evaluate the performance of a solar water heating system with evacuated tube heat pipe collector. First, a mathematical model was presented according to thermal and exergy analysis to analyze the collector performance and then the given system was constructed and experimentally tested according to a real consumption pattern. The obtained results showed that the optimal number of collector pipes was reported to be 15. Also, a direct association was found between hot water consumption and system performance. The trend of changes for exergetic effi- ciency is ascending as the time is passed. At the end of the day, this efficiency reaches its maximum level, around 5.4%. The maximum outlet temperature of collector was about 64 C, which occurred between 15:00 and 16:00 pm. In the early morning, an auxiliary system was required; however, this support system went off cycle after 14:00 pm and the solar cycle alone supplied the required energy. The comparison of theoretical and experimental results was indicative of the capability of the developed model in predicting the performance of heat pipe solar water heater with maximum relative error of 8.4% and the maximum standard error of 1.91%
