We used this window fan for the first time last spring, through the fall.  I have never seen a window fan this powerful in 40 years.  The most wonderful thing is when this fan pulls in the cool night air into our bedroom.  When we are sleeping. And in the morning we wake to coolfresh morning air.  When you have the fan in a window in one room, and you crack the window open in another room.  This fan causes a nice flow of air thought the first or second floor of our house.  This Dan has also cut down on our air conditioner use substantially.  I HIGHLY RECOMMEND RHIS PRODUCT.