An original R22 wall room air conditioner with a cooling capacity of 2.4 kW and energy efficiency ratio (EER) of 3.2 is retrofitted with a compressor of a 20% larger displacement to charge R290 and R1270 for performance experiments. The results show that for R1270, only adopting a same kind mineral lubricant of higher viscosity would supply 2.4% higher cooling capacity and 0.8% higher EER than those of the original R22 system under normal condition, and for R290, adopting the larger displacement compressor simultaneously would also obtain better performance. Alternative systems all have higher increase rate and greater increment in both cooling capacity and EER than the original R22 system when outdoor temperature decreases. The R1270 system has great increase in cooling capacity and negligible decrease in EER. Refrigerant charge distribution is also investigated and it indicates that the charge within both heat exchangers and compressor ought to be reduced.