Essentially the main reason for the decrease of capacity and COP at extreme ambient conditions is due to the reduction of refrigerant mass flow rate. Through the thermos-physical property comparison between R410A and R32 it’s known that the density difference between R410A and R32 is around 28%, and therefore the ideal mass flow rate difference should be close to 28%. However, the refrigerant mass flow rate difference was much larger than 28% for extreme cooling and heating conditions. This indicates that the compressor underperformed when R32 was used in these conditions. Comparing the power consumption of a vapor-injected system to a non-injection system at the ambient temperature of 46 #C, there is a significant power increase. This is because the compressor needs to compress the additional refrigerant injected to the compressor. Moreover, vapor injection is generally more beneficial for low temperature heating mode than for high temperature cooling mode. Therefore, this unfavorably increases the compressor load at 46 #C, and therefore leads to lower compressor efficiencies. It should be noted that this study is a drop-in test comparison, and therefore the lubricant remains the same for R410A and R32. Proper selection of lubricant for R32 can also potentially improve the system performance. However, it is not within the scope of this study, and therefore it is not discussed in detail here. In overall, vapor injection is more beneficial for R410A than for R32 in the current system setup through drop-in tests. The problem with R32 is that the high compressor discharge temperature and low compressor efficiency lead to overall low performance in vapor injection mode, especially for extreme cooling and heating conditions. Both the compressor and the heat exchanger need to be optimized to fit R32 in order to achieve better performance in a vapor injection cycle.