The authors established a technique for measuring calorie output from a variable refrigerant flow air conditioning system by applying the refrigerant enthalpy method. In this paper, the advantages of the measuring technique and its detailed estimation process of the calorie output are introduced. In addition, the measurement with water cooled variable refrigerant flow air conditioning system was carried out in order to confirm the accuracy of technique. In this actual measurement, it was shown that measuring the appropriate pressure of refrigerant in the heat pump is important to achieve the measurement accuracy. As the another results of actual measurement, the error of estimation values of heat quantity between the established technique and the conventional one is less than 20 % for cooling and heating, respectively. Therefore, the technique for measuring calorie output that the authors established has the high measurement accuracy. In addition, the authors suggested operation improvement method by analyzing measured values such as pressure, calorie output, electric power consumption and so on. As the results, it was confirmed that COPs is improved in the cooling period by lowering the high side pressure of refrigerant in the heat pump depending on the inlet water temperature in the primary side of the pump.