Abstract: A solar energy collector panel has inlet and outlet header tubes provided with longitudinal slots which terminate short of ends of the header tubes and the ends of a matrix panel extend into those slots and are sealed to the header tubes and provides flow channels between the headers. A water circulating pmp and valve arrangement pumps water from a pool, through the collector and back to the pool only when available radiant energy is sufficient to further heat the water. Control of the pump and valve is effected by comparing signals from an infrared sensor near the collector panel and temperature sensor in the pool.