Abstract: An automatic freeze protection system for solar energy collector apparatus. The apparatus includes a solar collector for circulating water or another fluid to be heated by the sun. Sensor means are provided within the collector to monitor the temperature of the water, and whenever it approaches the freezing point, the sensor will automatically actuate a valve means to rapidly drain the water from the collector. When the temperature within the collector thereafter rises to a predetermined safe level, the sensor means will again automatically actuate the valve means to refill the collector with fresh water to be heated. The system provided thus avoids the need for anti-freeze or other freeze protection materials suggested by the prior art as well as isolated water loops, heat exchangers and other expensive safety equipment necessitated thereby.