Performance of a hot water solar collector system has been investigated and assessed in this work. Solar energy is one of the essential natural energy sources that can be used to provide hot water for daily use in sustainable buildings. A mobile solar collector has been designed and built to assess the hot water solar collector system in different regions of Iraq. A flat plate solar collector with a helical coil heat exchanger has been used in this study. The average solar radiation has been predicted and measured. The results revealed that there is high performance of the solar water collector panel to produce hot water for buildings in Iraq. The maximum outlet temperature of the hot water of 54 ± 0.1 oC was recorded at the shell flow rate of 4 l/min and coil flow rate of 1 l/min. Maximum output energy of the solar collector system ranging from 13567 to 1488 ± 10.5 W/m2 was recorded at the range of ambient temperature from 10 to 49± 0.1 oC and sun intensity of 1890 W/m2. The outcome of this work is a real database which will provide a good reference for future research and energy applications in Iraq.