The aim of the current study was to develop a new temperature controlled solar water heater (TCSWH). Therefore, process control equipment and solenoid valves were used in the TCSWH system for the development. TCSWH was experimentally analyzed at 40 degrees C, 45 degrees C, 50 degrees C and 55 degrees C and it was also compared with the thermosiphon system. A detailed comparison was performed by calculating stored energy, storage tank water temperatures, storage tank water amounts and system efficiencies for both of the systems. As a result, the TCSWH system could provide water temperature at the set value with +/-2 degrees C accuracy. In the TCSWH system, the highest average efficiency was obtained as a result of the experiments carried out at 40 and 45 degrees C. In solar water heaters, efficiency is not the only indicator of usable energy amount in the system storage tank. Although efficiencies of the systems of which water amounts at low temperature are high, the energy they store is useless energy. For that reason, the importance of useable energy in the storage tank was emphasized with graphics by comparing TCSWH system to the thermosiphon system. The amount of water was obtained as 84 kg when the control device was set to 45 degrees C in the TCSWH and the amount of water in the thermosiphon system was obtained 52 kg at the same temperature. In addition to average energy efficiency was obtained as 65% for the TCSWH and 60% for the thermosiphon system. (C) 2012 Elsevier B.V. All rights reserved.