The big question here is what is your goal, is it to increase peak summer pool temperature or is it to extend the swim season. In your region in central Florida it is possible to get a near 12 month swim season with solar, however it is a LOT easier to get a 10 month swim season, and takes fewer panels, the problem is there is just not that much energy in the winter time sunlight, that combined with somewhat shorter days and you take a double hit on solar performance. As a result the shoulder seasons can be a bit unpredictable if you don't have excessively sized solar. What tends to happen with my setup in the fall at some point we will have a cold front and several cloudy days, then more warmish weather, however by this point the solar heater can never regain the heat lost during those cold and cloudy days. In the Spring the reverse happens, for example this year with our mild winter my pool temperature never dropped much below 70 degrees, however it was not until early February that it broke 80 degrees, and not until early April that it started maintaining my cut off set point of 84 degrees, all of this with a solar cover on the pool, now at the first of May it will maintain that 84 degree set point without a cover even though we are having a high today of only about 75 degrees and most days barely break 80. (warm winter/ cool spring this year). Personally I like my pool water cooler than most people and put my comfortable minimum temperature cut off around 78 degrees (as I get older this number goes up, not that many years ago (or so it seems) my ideal pool temperature was about 78 or 79, now it is 83/84)
Ike
p.s. I would suggest getting at least 3 bids from the major players, Fafco, AquaTherm, Techno-Solis, as well as Helicol
also regardless of which you go with get a solar controller if you don't already have an automation system that supports solar heat
