Abstract: A closed circuit solar heating system in which hot air from the upper end of a southwardly sloping flat-plate solar heat collector is circulated through a lower heat exchanger in the lower portion of an upright insulated heat storage tank filled with liquid storage medium (water) and back through the collector for reheating the air as it flows through the collector from the lower end to the upper end thereof. The hot air flowing through the lower heat exchanger transfers heat to the water in the tank for storage. The system is further characterized in the provision of an upper heat exchanger in the upper portion of the tank to transfer heat stored in the water in the tank to room air circulated through the upper heat exchanger. Hot water for domestic use is provided by installing a coiled water supply tube in the heat storage tank.