The invention relates to an on-board assembly for producing and storing electricity, including at least one hydrogenerator having an output line connected to at least one electrical battery having predetermined electrical load parameters. The hydrogenerator includes a load-bearing structure onto which a generator and an impeller, secured to a shaft for driving a rotor of the generator, are mounted. Said assembly is characterized in that the generator is an excitation generator, and the hydrogenerator includes a rectifier circuit, connecting the generator to the output line, and at least one circuit for exciting the generator. The excitation circuit is connected to an excitation current regulator controlled by a control unit set up so that the generator provides a load current consistent with the electrical load parameters on the basis of a resisting torque of the generator, said torque being predetermined so as to limit drag of the impeller.