This paper describes a study to experimentally determine the steady-state characteristics, cyclic effect, and frosting/defrosting effect of a inverter heat pump currently available on the Japanese market and compute its seasonal efficiency based on the local outdoor air temperature data.

It has been found that the APF of this heat pump is higher by 15% than that of the conventional fixed-speed heat pump. If cyclic and frosting/defrosting losses are eliminated, the APF of the inverter heat pump will be further improved by 2%to 6%. For the evaluation of an inverter heat pump, APF alone is not sufficient, and an additional parameter such as an annual comfort factor (ACF) is needed.

Units: SI