A powered garage door opener is provided for mounting to a garage wall adjacent to the garage door in a side-mounted configuration. The powered garage door opener includes a power unit containing an electric motor, a reduction gearset driven by the electric motor, and a tubular output member driven by the reduction gearset. The output member defines a pass-thru aperture configured to drivingly couple to a coupler unit that is pre-assembled onto the garage door shaft. The power unit is non-handed so as to permit installation at either or both ends of the shaft, as well as in a paired side-by-side relationship along one end.