A linear generator apparatus includes first and second elongate coaxial bodies that are axially movable relative to one another with a reciprocating movement. The first body is axially and freely movable relative to the second body within a predetermined displacement range or free zone. A helical spring connecting to both first and second bodies biases the first body toward the free zone relative to the second body when outside of the free zone. An electrical power generator mounted on both first and second bodies generates power when the first and second bodies axially move relative to one another within the free zone and beyond. The invention also relates to a suspension system for motor vehicle that includes a coil spring and the apparatus in replacement of a conventional shock absorber.