Lunar-Resonant Streetlights Shine Only When the Moon Doesn't Shine

Streetlights aren't really necessary when there's a full moon out, what with it bouncing all that sunlight down at us and everything. But your average streetlight isn't smart enough to know when it isn't needed, so it sits there, dumbly shining away for no real reason.
That's not the case with the Lunar-Resonant Street Lights, conceptual LED-based lamps that dim down and turn off completely as the moon waxes. When it's a new moon, it'll be fully lit up, showing you your path. What results is an energy savings of 90-95%. Not a bad idea.