This study measures the COPs of R32/R1234ze(E) and R32/R1234yf with GWPs of approximately 285 and 190 with a vapour compression cycle under two heating modes, where the heat sink water change temperature 10 K and 25 K. At a temperature change of 10 K, the COPs of mixtures are significantly lower than that of R410A. At a temperature change of 25 K, the COPs of mixtures are generally comparable to that of R410A. When the temperature change in heat sink fluid is large, the larger temperature glide of the combination R32/R1234e(E) is somewhat advantageous to reduce the irreversible loss in condenser. The smaller volumetric capacity of refrigerant mixture significantly increases the volumetric flow rate and the irreversible loss in the compressor at higher heating loads. The pinch point of R410A appeared in the condenser caused excess pressure rising and increased compressor loss at a temperature change of 25 K.