A thermal collection system has a first tank for storing relatively hot working fluid and a second tank for storing relatively cold working fluid. A heat exchanger is connected for receiving the relatively hot working fluid from the first tank for providing heat to the heat exchanger. The heat exchanger discharges the working fluid at a lower temperature than a temperature of the relatively hot working fluid of the first tank. A solar panel collector is connected for receiving the lower temperature working fluid from the heat exchanger and for heating the lower temperature working fluid and feeding same to a first control valve. The first control valve is operative for feeding working fluid from the solar collector selectively to one of the first tank and the second tank. The second tank has a second control valve selectively operative for permitting working fluid from the second tank to flow to the solar collector. Improved collection efficiencies in the solar collector may be obtained using the two tank structure for passing working fluid through the solar collector.