Abstract In this study, an overview of the system performance of R-1234yf in association with R-134a is carried out. Based on the existing researches, it is found that the COP and heat capacity of R-134a system may suffer from direct drop-in replacement of R-1234yf. The deterioration is around 0–27% depending on the operational conditions. With the introduction of internal heat exchanger, ejector, expander, or adjustment of the thermal expansion valve, the deterioration can be relieved, and a comparable performance becomes likely. For the heat transfer performance in the evaporator, R-1234yf is almost comparable with that of R-134a. However, the performance in the condenser is inferior to R-134a. The phenomenon may be quite severe for a water cooled condenser since the dominant thermal resistance may fall in the refrigerant side. The volumetric efficiency of R-1234yf system is slightly lower than that of R-134a due to higher frictional drop of R-1234yf. For the same thermal expansion valve for controlling the suction superheat, it appears that higher suction superheat may occur for R-1234yf refrigerant. Hence further adjustment of spring in the valve is required for soft optimization.