The setup I'm going with seems more common with IGP, so I'm hoping I can get by with a panel area slightly less than 50% of the pool surface area given I don't have a deep end to the pool. This is for eastern Iowa (latitude is south of Chicago). Full sun, south exposure on ground racks figuring ~ 30 degree incline. I'll be using 4X12 FAFCO (2 inch header) panels and a Goldline controller. 15 X 30 oval AGP (no deep end - standard 52 inch side-walls). We religiously use a 12 mil diamond (blue/silver) solar cover at night. Just want to get the pool into the mid-80's (85?) by late May and keep it there through perhaps mid-September.
I'm thinking four panels are going to work just fine (that's what I ordered), but since I haven't started building the rack yet now's the time to buy a fifth if someone here thinks I"m undersizing. The south yard faces the street and my wife isn't crazy about an industrial-looking bank of panels. Four will fit nicely - five will start to look a little intense.