Abstract: A superior performance passive solar water heater of the type combining heat absorber and storage in a tank adapted to minimize heat loss due to night time re-radiation, wind, and other methods by which a solar heater loses heat due to radiation, conduction, and convection of the heat from the water heater. More specifically, improvements are made to substantially reduce the water storage tank heat radiation, to maintain the tank a substantially air-tight environment, to interrupt in the heat conduction path from the tank environment, to remove the hottest water first from the heated tank, and to introduce cold water into the tank in such a manner as to miniminally disrupt the heated water in the tank.