There are over 300,000 swimming pools in Florida, and most of them must be heated during winter months to maintain comfortable swimming conditions. For the average user, temperatures ranging from 78 °F to 80° F for spring and fall and 76° for winter are usually considered comfortable. This publication presents a simple method that can be used to determine the solar collector area (within ± 20 percent) needed to heat a swimming pool to comfort conditions assuming average weather patterns.
Florida Solar Energy Center and Cromer, Charles, "Solar Swimming Pool Heating In Florida: Collector Sizing And Economics" (2000). FSEC Energy Research Center®. 656.