A method of operating an air/water heat pump comprising a compressor, a first heat exchanger, through which water flows, an expansion valve, a second heat exchanger exposed to air, and a first and a second diverter valve (50, 60), wherein, in at least a first and a second mode, the first and the second diverter valve (50, 60) of the heat pump apparatus are switchable such that each of the compressor, the first heat exchanger, through which water flows, the expansion valve, and the second heat exchanger exposed to air can be coupled to the first diverter valve at their first end and to the second diverter valve at their second end, comprising the steps of: in the first, heating mode, switching the first and the second diverter valve (50, 60) such that the first heat exchanger, through which water flows, is coupled as a condenser to the compressor at its first end and to the expansion valve at its second end, wherein the compressed refrigerant flows from the compressor to the first heat exchanger and from the first heat exchanger via the expansion valve to the second heat exchanger exposed to air, and from the second heat exchanger exposed to air back to the compressor, in the second, cooling mode, switching the first and the second diverter valve (50, 60) such that the first heat exchanger is coupled as an evaporator to the expansion valve at its first end and to the compressor at its second end, wherein, in the second, cooling mode, the refrigerant flows from the compressor to the second heat exchanger exposed to air as a condenser, from the second heat exchanger exposed to air to the expansion valve, and from there to the first heat exchanger as an evaporator, and finally back to the compressor, and wherein the flow direction of the refrigerant through the second heat exchanger exposed to air and the flow direction of the refrigerant through the first heat exchanger, through which water flows, are the same in both the first, heating mode and the second, cooling mode, wherein by providing the two diverter valves (50, 60), the second heat exchanger exposed to air and the first heat exchanger, through which water flows, are operated in countercurrent both during heating and during cooling, for which the two diverter valves (50, 60) are arranged such that the first heat exchanger, through which water flows, the expansion valve, the second heat exchanger, through which air flows, and the compressor are coupled in parallel between the first and the second diverter valve (50, 60). in the first, heating mode, switching the first and the second diverter valve (50, 60) such that the first heat exchanger, through which water flows, is coupled as a condenser to the compressor at its first end and to the expansion valve at its second end, wherein the compressed refrigerant flows from the compressor to the first heat exchanger and from the first heat exchanger via the expansion valve to the second heat exchanger exposed to air, and from the second heat exchanger exposed to air back to the compressor, in the second, cooling mode, switching the first and the second diverter valve (50, 60) such that the first heat exchanger is coupled as an evaporator to the expansion valve at its first end and to the compressor at its second end, wherein, in the second, cooling mode, the refrigerant flows from the compressor to the second heat exchanger exposed to air as a condenser, from the second heat exchanger exposed to air to the expansion valve, and from there to the first heat exchanger as an evaporator, and finally back to the compressor, and wherein the flow direction of the refrigerant through the second heat exchanger exposed to air and the flow direction of the refrigerant through the first heat exchanger, through which water flows, are the same in both the first, heating mode and the second, cooling mode, wherein by providing the two diverter valves (50, 60), the second heat exchanger exposed to air and the first heat exchanger, through which water flows, are operated in countercurrent both during heating and during cooling, for which the two diverter valves (50, 60) are arranged such that the first heat exchanger, through which water flows, the expansion valve, the second heat exchanger, through which air flows, and the compressor are coupled in parallel between the first and the second diverter valve (50, 60).