A generator assembly suitable for being carried on the back of a human comprising an internal combustion engine, an alternator and a shaft driven by said engine and driving said alternator wherein when said generator assembly is being carried on the back of human said shaft is substantially parallel to a longitudinal axis of said human. This enhances the manoeuvrability of the assembly. Preferably the assembly comprises a generator module having an engine and an alternator coupled directly by a common shaft, the generator being attached to a frame of the assembly at only two longitudinally spaced-apart positions.