Complex sentence: Even with the high per-unit cost, the increase in efficiency and increased lifespan make them very attractive for street lighting use; the reduced cost of electricity and maintenance in many cases can offset the increased cost of the lamp.
Split into simpler sentences: Even with the high per-unit cost, the increase in efficiency and increased lifespan make them very attractive for street lighting use. The reduced cost of electricity and maintenance in many cases can offset the increased cost of the lamp.