I don't even turn the lights on in my tanks cause I have enough ambient light. Unless your room is very dark I don't see a need to turn the canopy on. I do turn them on once in a while so they don't get freaked out w/ having no lights at all for a long period of time.
You can always remove bulbs to see how much light is being distributed inside the tank. I just feel there's no need to waste electricity when I'm not growing plants either.
