Refrigerant and heat exchanger design are significant factors of interest in Heat Pump Water Heater (HPWH) system. This paper presents the experimental study about R1234yf as a low global warming potential (GWP) drop-in substitute of R134a. Then condenser configuration analysis is conducted to explore the effects of condenser circuit number using the baseline R134a. It is experimentally demonstrated that the cooling capacity and COP obtained with R1234yf in a HPWH system is slightly lower than that obtained with R134a. It has been shown that R1234yf can be a desirable alternative for R134a with comparable performance but it is noted that extensive modifications should be considered if the same system performance need to be obtained. By closing the valves at the inlet and outlet of one condenser circuit, a one-circuit condenser system could be achieved. It is shown that a system operating with one-circuit condenser only brings the COP down within 5.5%.