In this work, an innovative design for a solar water heating system using a flat-shaped heat pipe as a heat transfer device is presented to pave the way for a substantial increase in the thermal performance of these systems. An analytical study is utilized to investigate the thermal performance of the solar water heating system. The analytical results of the flat-shaped heat pipe system are compared with the results of the evacuated tube solar water heating system with a U-tube, thermosyphon, and closed-loop pulsating heat pipe. It is found that the water temperature difference between the inlet and outlet of the flat-shaped heat pipe system is substantially higher than the U-tube, thermosyphon, and closed-loop pulsating heat pipe system by as much as 31.4, 22.5, and 18.5 °C, respectively, at a nominal 0.6 l/min mass flowrate. Furthermore, utilizing the flat-shaped heat pipe in the solar water heating system optimizes the thermal conductivity of the solar setup due to a reduction in the condenser section length. These reductions also lead to a large reduction in the weight and cost of the system.