Whatever you do, don't buy a Nicro Solar minivent 1000 like this:
Loud, the slightest shadow makes the fan stop (since it includes no internal battery), doesn't move a lot of air.
I guess you get what you pay for. I bought it because it was a direct replacement for the non-functioning one on my boat. I definitely should have spent more and got one of better quality. LIke one of the day/night kind with an internal battery.