Abstract: An educational device for use in instruction concerning solar heat utilization comprises a solar energy collector in which liquid is heated by solar energy indirectly through a heat-exchanger, a liquid storage tank, a pump and associated pipe system to circulate liquid between the collector and the storage tank, a valved by-pass line to permit recycle of liquid from and to the storage tank external of said collector and an instrument panel to display temperature of said heat exchanger, temperature of liquid contained within said collector, temperature of liquid contained in said storage tank and pressure of liquid flowing in said pipe system.