Pilot,
I have a 28' by 54" deep above ground, and live in upstate New York and my water temp was 82 today. I have one 4 x 20 panel mounted on plywood at a 45 degree angle, you can see pics in the above ground pool and equip section under the solar panel mount thread. Three of my neighbors have pools, but we were the only family swimming on Memorial Day, probably the best $200 I have spent on pool "stuff" so far. My temp has risen about 4 degrees each warm day.