While aH, watts, etc are important.....it really boils down to how efficient a fan is at those figures.  I have one fan that only uses .5 amps on high; however, it moves very little air, even on high.  The Fantastic Fan puts out far more air (cfm) than any fan I've ever used.  You can't compare fans simply by how much power they use.  My camper has been solar powered for 14 years and I do pay close attention to amp draw, but efficiency is critical to me.  I wouldn't even think about using battery power without a way to replenish