In this paper the attention is focused on introducing the initial experimental results of a comparative experimental investigation on the energy performances of R600a tested as drop-in of R134a in a test-bench refrigeration system developed at the School of Mechanical Engineering of VIT University located in Vellore (India). Moreover, a comparison of the energy performances was pursued also with the system working with and without sub-cooling. The initial experimental investigation is performed respecting the requirement that the two fluids occupy the same volume. The initial energy performances are carried out in terms of evaporator temperature, coefficient of performance and refrigeration effect. The effect of drop-in with R600 a system previously working with R134a, carries an enhancement of the energy performances in terms of COP and refrigeration effect. Moreover, subcooling carries to an additional benefit on the refrigeration effect. The introduced initial experimental results constitute just the first step of a bigger investigation to be conducted in India, focused on analyzing the impact of the drop-in of HFC with new eco-friendly refrigerants.