PURPOSE: To enhance the efficiency by a simple structure wherein a burner-fired chemical heat pump is put into operation while being backed-up by leading the solar heat to an evaporator.

CONSTITUTION: When a burner 1 is turned ON, the water contained in zeolite 3 serving as an absorber, which is incorporated in a combined generator and absorber 2, is adsorbed and condensed at a condensing part 4, resulting in giving off the heat of condensation to a water conduit pipe 8 and sending to a heat storage tank 10. At this time, the zeolite 3 turns into dry state. After that, the burner 1 is turned OFF and a delivery hot water pipe is changed-over from the water conduit 8 to a water conduit 7 in order to recover the heat of absorption. The evaporator 5 also serves as the storage vessel of the condensed water and is heated by the solar heat sent from a solar system 6. In such a manner as described above, the structure is simple and at the same time the enhancement of the efficiency is resulted.