16-Tube SunChaser Solar Hot Water Collector 20.5KBTU/Day ?Collector includes manifold, 16 vacuum tubes with heat pipes, Solar Hot Water Heater work station consists of : ?Wilo pump model Star RS 15/6 (Variable Speed Pump 52/75/96 Watts) ?Expansion tank ?Solar controller model SR868C8 ?Temperature sensors ?Accessories for installation This solar water tank is equipped with built in single coil copper heat exchanger, and electric secondary/back up heating capability when solar collector does not produce enough heat typically during Winter months. This solar hot water tank can be installed alone as the primary hot water tank or together with a gas or electric heater as a pre-heat solar water tank.