The performance of a refrigeration cycle driven by a liquid refrigerant injected compressor is investigated to examine its energy saving characteristics and performance improvement. Mathematical models of the compressor, the condenser and their combination in a complete cycle are used. The model shows an increase of the suction mass flow, an associated increase of the compression power and a small change of the overall efficiency due to the reduced temperatures of the refrigerant discharge and the compressor body. A condenser fed with refrigerant of lower superheat and greater mass flow shows an improvement in performance due to an increase in the two-phase region, though the improvement depends on the secondary fluid flow conditions. The thermal capacity and coefficient of performance of the total cycle increases with the injection ratio due to the combined effects of the compressor and the condenser.