Air-conditioning and heat pumping performance of R32/R152a mixture is measured in the composition range of 20-50% R32 with an interval of 10% for the comparison with HCFC22 in a water source heat pump bench tester. Tests are carried out under the same capacity in the bench tester equipped with a variable speed open type compressor at the evaporation and condensation temperatures of 7/45 degrees C and -7/41 degrees C for summer and winter conditions, respectively. Test results show that the compressor power of R32/R152a mixture is up to 13.7% lower than that of HCFC22 while the coefficient of performance (COP) of R32/R152a mixture is up to 15.8% higher than that of HCFC22. From the view point of energy efficiency, R32/R152a mixture is excellent as compared to HCFC22. Compressor discharge temperatures of R32/R152a mixture are increased up to 15.4 degrees C as compared to those of HCFC22. The amount of charge for R32/R152a mixture is decreased up to 27% as compared to that of HCFC22. Overall, R32/R152a mixture is an excellent long term solution to replace HCFC22 in water source heat pumps under the similar evaporator and condenser temperatures. The flammability study shows that the mixture is virtually not flammable at the 'drop-in' composition of 36%R32/64%R152a. (C) 2012 Elsevier Ltd. All rights reserved.