moonlight power
Under a full moon, the PV panels on the roof will register a couple watts o' power. Not enough to spin the meter backwards, but cool.
I used to live in a rather dark little house. I would use mirror tiles in the yard to bounce sunlight through a window to make it brighter. Nice, bur every half hour I had to go out and reset the mirrors. The light in the house was wonderful. I'd do the same during a full moon.