The invention relates to a power generation apparatus (1), in particular for expanding the range of an electrically operated vehicle, having an internal combustion engine (5) and a generator (6), which is situated coaxially to the output shaft (7) of the internal combustion engine (5), internal combustion engine (5) and generator (6) being situated in a housing (2, 3) through which cooling air flows. In order to increase the power density, minimize the noise emission, and allow a compact construction, it is provided that internal combustion engine (5) and generator (6) are implemented as a unit (10) and are situated in a substantially tubular cooling chamber (4) formed by an inner housing, an intake air duct (8) opening into the cooling chamber (5) on the side of the generator (6), preferably approximately in the area of the output shaft axis (7′), and an exhaust air duct (9) originating from the cooling chamber (4) on the side of the internal combustion engine (5), preferably in the area of the output shaft axis (7′), and the internal combustion engine-generator unit (10) being mounted in the housing (2, 3) via noise-damping engine bearings.