The Powernet Compact Flat Plate Solar Water Heater is an indirect system. The heat source mainly relies on the solar energy. The jacket layer of the tank forms a circulation with 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 at 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 flows to the bottom of the heat collector through the down pipe of the jacket layer, while the hot medium comes to the jacket layer through the upper pipe. The jacket layer exchanges heat with the domestic water in the tank. 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.