This is the best solar attic fan on the market. Price, lifetime guarantee, 48 watt unit is absolutely unbeatable. I compared it to two other solar fans in my attic, and this one clearly moves a lot more air for just a little more money. The fan seems to turn twice as fast, and it really gets going with just a little light. For a little more money you're moving a lot more air. And, Infinigi.com has the best prices, $50–$100 less than Amazon, others.