I compared these panels with a competitor brand and these were significantly less expensive but the competitor brand had a 12 year warranty and these only had a 5 year warranty. However the price difference was significant enough that I could purchase 2 of these for less than the competitor panels. I therefore decided to purchase these panels. I purchased 5 of the panel packages and had them mounted on the roof. I have them controlled by a thermatic controller (thermatic valve). On the very first day of operation (early May) pumping only 4 hours (no increase to my filter duration) it raised the temperature ~12 degrees (to 82 degrees F). By the second day the temperature had hit our thermatically controlled setting point of 84 degrees. I suspect we will easily extend our swim season by ~4 months (used to be June through early Oct, now I suspect it should be Mar through ealry to mid Nov). This is exactly what I was hoping for when I purchased these panels. I do recommend getting and using a thermatic controller with these panels. So first week installed they are operating great. Now I just need them to continue to operate as well for at least 5 years. If they fall apart in less than 5 years then I should have gone with the other panels.