I had Fafco's "SunSaver" panels installed when we did our pool. Since we had a South facing roof (two story), the dealer recommeded 75% of the surface area of our pool. The panels are 4x12 and they installed 7 panels. The total cost out the door was $4000. It was very straightfoward and didn't include any trenching. Today, my pool was 81 degrees while my neighbors similar pool with the same sun exposure with no solar is at 68. What the others have said I was told as well, and that's North facing will not yield the same results.