A lighting unit including at least one elongated substrate having a plurality of light-emitting optoelectronic devices mounted thereon and an elongated housing supporting the elongated substrate. The housing includes integrally-formed reflectors positioned adjacent the optoelectronic devices. The lighting unit also includes a translucent output panel that transmits light from the optoelectronic devices. The light unit has a first wiring harness for connection to a power source, and a second wiring harness connectable to an adjacent lighting unit.