This paper presents results of performance tests for R-22 and four alternative fluids (R-134a, R-32/134a (30/70%), R-407C, and R-410A) at operating conditions typical for a residential air conditioner. The study was performed in an experimental breadboard water-to-water heat pump in which a water/ethylene glycol mixture was used as the heat transfer fluid. The heat exchangers representing the evaporator and condenser were counter flow and cross flow, respectively. In tests performed at the same capacity, R-410A had the highest coefficient of performance. Test results for the system and data characterizing the performance of the heat exchangers and compressor are presented. The impact of the wide variations in the different alternative fluid properties on the system's operation and performance is particularly noted. The benefit of the liquid-line/suction-line heat exchange cycle is also addressed.