[en] This paper deals with an exergy analysis of the impact of direct replacement (retrofit) of R12 with the zeotropic mixture R413A on the performance of a domestic vapour-compression refrigeration system originally designed to work with R12. Parameters and factors affecting the performance of both refrigerants are evaluated using an exergy analysis. In the literature, no experimental data for exergy efficiency are reported, so far, for R413A. Twelve tests (six for each refrigerant), are carried out in a controlled environment during the selected cooling process from evaporator outlet temperature from 15 deg. C to -10 deg. C. The evaporator and condenser air-flows are modified to simulate different evaporator cooling loads and condensers ventilation loads. The overall energy and exergy performance of the system working with R413A is consistently better than that of R12.