Abstract: A solar powered heater system which may be employed to preheat water in or prior to delivery to a conventional hot water heater. The solar powered heater system includes a heat exchanger which is formed from a tube having a contoured surface. This tubular heat exchanger is inserted in a tank through which the liquid to be heated passes. The heat exchanger is part of a closed loop, through which a heat transfer fluid is circulated, which includes an array of solar collectors. The heat transfer fluid may either be bypassed around the heat exchanger or caused to stop circulating when insufficiently heated by the solar energy.