We bought one of these 4x20 ft panels with the bypass value and it works great. On a sunny day in the mid-80's it will raise the pool temp at least 5 degrees, that's on a 24ft round pool of 13,500 gallons. So, two days in a row will raise it about 10 degrees. We are swimming while the neighbors are sitting it out. My husband did build a raised structure for it to sit on since we didn't want it on the ground. It faces south, the angle can be adjusted, and he covered it with chicken wire. Before the chicken wire was added we had trouble with cats climbing on it and it also blew off in a storm. We haven't had to put it away for the winter yet; that will be another adventure.