A hybrid chiller system comprising: a GHP outdoor unit including a gas engine and a GHP compressor that compresses a refrigerant by a driven force of the gas engine; an EHP outdoor unit including a compressor to be driven by a commercial power source when it is used; and a water heat exchanger that exchanges heat between a refrigerant and cold and hot water that are sent from the GHP outdoor unit and the EHP outdoor unit, the hybrid chiller system performs a chiller air conditioning that produces cold and hot water by exchanging heat with a refrigerant by the water heat exchanger, the hybrid chiller system further comprising: a GHP control section that controls the GHP outdoor unit; an EHP control section that controls the EHP outdoor unit; and a controller control section that transmits a control instruction signal to each of the GHP control section and the EHP control section, characterized in that the controller control section is configured to: set an upper limit horsepower based on an operation state of each of the GHP outdoor unit and the EHP outdoor unit, and transmits an instruction signal of this upper limit horsepower to each of the GHP control section and the EHP control section, in a case where air heat exchange air conditioning is performed by suppling the refrigerant from the GHP outdoor unit and the EHP outdoor unit to an indoor heat exchanger of the indoor unit in place of the water heat exchanger, when an operation horsepower of the EHP outdoor unit does not satisfy an upper limit horsepower instruction of the EHP outdoor unit, the EHP control section notifies the GHP control section of the upper limit horsepower instruction not being satisfied, and the GHP control section performs control to lower rotation of the gas engine of the GHP outdoor unit, and when chiller air conditioning is performed and a heating operation is performed, the GHP control section executes control so that the control to lower the rotation of the gas engine of the GHP outdoor unit is not performed. a GHP outdoor unit including a gas engine and a GHP compressor that compresses a refrigerant by a driven force of the gas engine; an EHP outdoor unit including a compressor to be driven by a commercial power source when it is used; and a water heat exchanger that exchanges heat between a refrigerant and cold and hot water that are sent from the GHP outdoor unit and the EHP outdoor unit, the hybrid chiller system performs a chiller air conditioning that produces cold and hot water by exchanging heat with a refrigerant by the water heat exchanger, the hybrid chiller system further comprising: a GHP control section that controls the GHP outdoor unit; an EHP control section that controls the EHP outdoor unit; and a controller control section that transmits a control instruction signal to each of the GHP control section and the EHP control section, characterized in that the controller control section is configured to: a GHP control section that controls the GHP outdoor unit; an EHP control section that controls the EHP outdoor unit; and a controller control section that transmits a control instruction signal to each of the GHP control section and the EHP control section, characterized in that the controller control section is configured to: set an upper limit horsepower based on an operation state of each of the GHP outdoor unit and the EHP outdoor unit, and transmits an instruction signal of this upper limit horsepower to each of the GHP control section and the EHP control section, in a case where air heat exchange air conditioning is performed by suppling the refrigerant from the GHP outdoor unit and the EHP outdoor unit to an indoor heat exchanger of the indoor unit in place of the water heat exchanger, when an operation horsepower of the EHP outdoor unit does not satisfy an upper limit horsepower instruction of the EHP outdoor unit, the EHP control section notifies the GHP control section of the upper limit horsepower instruction not being satisfied, and the GHP control section performs control to lower rotation of the gas engine of the GHP outdoor unit, and when chiller air conditioning is performed and a heating operation is performed, the GHP control section executes control so that the control to lower the rotation of the gas engine of the GHP outdoor unit is not performed.