PURPOSE: To average the consumption of electric power by a method wherein cold and hot water accumulating operations are performed in the midnight power supply time zone, the operation efficiency of the air conditioner in the daytime is increased at the time of cooling operation to thereby reduce the consumption of electric power and to carry out a counter- measure against a power peak-cut by using accumulated cold water and accumulated hot water is used in the early morning at the time of heating operation.

CONSTITUTION: The heat pump type air conditioner 1 including a compressor 14, a four-way changeover valve 15, a water cooling type service side heat exchager 16, pressure reducing mechanisms 17 and 19 and a serive side heat exchanger 20 all of which are connected through pipes, a cold and hot water heat exchanger 22 arranged parallel to the heat exchanger 20, a heat pump type chiller unit 2 and cold and hot water accumulating tank 3 divided into two sub-tanks 4 and 5 of different temperature are provided. Further, a cold and hot water pipe extending from the unit 2 is selectively connected to the sub-tanks 4 and 5 and cold and hot water pipes on the service sides of the sub-tanks 4 and 5 are selectively connected to the heat exchangers 16 and 22 so that the cold and hot water accumulating operations of the unit 2 are carried out. That is, to meat the power peak cut at the time of cooling operation, the air conditioner 1 is stopped and the cooling operation is performed by circulating the accumulated cold water through the heat exchanger 22 while when the air conditioner performs a high load heating operation, the accumulated hot water is circulated through the heat exchanger 22.