The present invention relates to the field of energy recovery from hot exhaust gases, a type of system that is widely used in industrial generator assemblies to produce steam used in industrial processes or cold to cool perishables or to cool environments. The system according to the present invention applies to the recovery of energy from exhaust gases in small generator assemblies, smaller than 10 MW, and comprises a turbo (1) connected to the exhaust gas outlet (2) in a small power plant generator assembly (3) and in which said turbo (1) is connected to a hydraulic pump (4), which generates pressure and transmits this pressure to a hydraulic pressure accumulator (5) which, in turn, sends hydraulic fluid under pressure for a hydraulic motor (6) of constant speed, which moves a pulley (7), and said pulley (7), in turn, moves another pulley (8), installed directly on the alternator shaft (9) of the generator assembly (3). In addition to pulleys (7,8), the movement can be done through a gear/clutch system or through a torque converter.