A walk-behind mower includes a frame, and a cutting unit connected to the frame and at least one cutting element. Interchangeable power unit support assemblies are each adapted to support either a reciprocating engine or a battery unit. One of the power unit support assemblies is releasably connected to the frame. An electric motor is provided to displace the cutting element. An output voltage generated by either the reciprocating engine or the battery unit mounted on the power unit support assembly energizes the electric motor.