My dad has been designing and selling restraunt ventilation equipment for his entire post college life (over 30 years) and I asked him about it. His answer. It is pure BS. That tiny fan is way too small to do any kind of real work, they close all the windows so no air can easily come back in (called make-up air in his business) so the efficiency is even worse as there is no draft (what air you remove has to be replaced some how) and the solar powered motor cannot be anywhere near powerful enough to spin the fan fast enough to make any sort of real difference. He said at most it might lower the temp by 1 or 2 degrees, but not the 50 or so they claim. He said you are way better off just cracking your windows as at least it will cause a draft.