Abstract: A system is provided for use with a solar collector. The system includes a water storage tank having a heat exchange element mounted therein, the tank being connected to one or more solar collectors adapted to heat water circulated through a primary loop by associated pumps. A secondary water loop connects to a heat exchanger at a waste heat supply source such as a furnace flue, for example, and provides supplementary heat to the water circulating in the primary loop. The storage tank forms part of a primary heat exchanger, the function of which is to provide means for heating water flowing through a coil in the tank for local use. A booster heater connected to the hot water outlet of the coil provides additional heat to the water during periods of high demand and/or poor conditions for heating water with the collector or the waste heat source.