the invention relates to an output controller for an engine control for an engine system comprising an internal combustion engine and in electric generator coupled to the internal combustion engine ; a computer device which is designed to receive a mechanical target output for the engine system and a maximally permissible rotational speed for the generator and to calculate a target rotational speed for the electric generator and an output torque for the internal combustion engine on the basis of the target output and the maximally permissible rotational speed ; an inertia compensating device which is designed to calculate a torque transmitted to a shaft of the generator by a mass moment of inertia of the internal combustion engine on the basis of a change of the target rotational speed for the electric generator and to calculate a target torque for the internal combustion engine on the basis of the transmitted torque and the calculated output torque of the internal combustion engine ; and an efficiency calculating device which is designed to calculate a degree of efficiency of the engine system on the basis of the target rotational speed for the electric generator , the calculated output torque of the internal combustion engine , a battery voltage and a generator current of a battery of the engine system , and the calculated target torque for the internal combustion engine and to adapt the value for the mechanical target output , which is supplied to the first computer device , on the basis of the calculated degree of efficiency . the invention further relates to an engine controller and to an engine system .