The Powernet Compact Flat Plate Solar Water Heater is an indirect system. The heat source mainly relies on the solar energy. Domestic water in the tank forms a direct circulation with the medium in the core passageway of the flat plate collector. The absorber coating of the collectors will absorb the sunlight, then convert sunlight into heat energy, and transfer the energy to the medium (water) in the core passageway through the absorber plate. While there will be a temperature difference in the medium(water) in the passageway, the density of hot water is less than that of the cold water, which will produce a buoyancy lift. In that way, the cold medium (water) flows to the bottom of the heat collector through the down pipe, while the hot medium (water) comes to the inner water tank through the upper pipe. Repeatedly, it heats all the water in the tank. Furthermore, the system has an electrical heater that can ensure sufficient hot water on days without sunlight.