This article experimentally studies the thermal performance of latent heat storage in a two-phase thermosyphon solar water heater; which utilizes the superior heat transfer characteristics of boiling and condensation, and eliminates drawbacks found in the conventional solar water heater Experimental investigations are first conducted to study the thermal behavior of tricosane (paraffin wax 116), water; and sodium acetate (NaCH3COO center dot 3H(2)O) used as energy storage materials. The results indicate that tricosane provides many advantages to be the energy storage material in the latent heat storage system. This study also examines the functions of charge and discharge thermal behaviors in a two-phase thermosyphon solar water heater. The results show that the system gives optimum charge and discharge performance under 40% alcohol fill ratio and with tricosane used as the energy, storage material, and displays an optimum charge efficiency of 73% and optimum discharge efficiency of 81%.