The purpose of this study was to develop a method for estimating the energy consumption of residential CO2 refrigerant heat-pump water heaters.This paper considered a calculation model involving the use of actual machine data analyzed in Part 1. It was evaluated by considering the effect of efficiency losses on the ideal system COP. The calculation model estimated "heat-pump COP", "storage heat loss" and "auxiliary power loss".The developed method was applicable to wide-ranging hot water supply conditions. The estimation and test values of the system COP agreed to within a tolerance of around ±0.2.
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