An electric generator device powered by a driving wheel of a motor vehicle. The device includes a base for supporting an electric generator. An idler roller assembly includes at least one load bearing idler roller mounted rotatably to the base for circumferentially engaging and supporting a driving wheel of a motor vehicle. A drive roller is mounted rotatably to the base for maintaining non-bearing circumferentially tangential interengagement with the driving wheel such that rotation of the wheel causes the drive roller to axially rotate. The drive roller is operably connected to the generator such that axial rotation of the drive roller is transmitted to the generator and the generator is operated to produce electricity.