To heat a swimming pool with solar requires a solar collector surface area that is between 60 and 100 percent of the surface area of he pool depending on the climate and on how many months of the year the owners wish to use the pool. In general, more square footage allows owners to have a warmed pool in cooler seasons.
In pool systems, the swimming pool serves as the storage tank, and the pools filtration pump circulates the pool water through the collectors. An unglazed flat plate collector, such as the SunEarth Oasis, is typically used in solar pool heating systems. A pool cover or blanket also reduces the heat loss and helps maintain warm pool temperatures for a longer period.
A backup heater is rarely needed for swimming pools, but is required to achieve the higher temperatures needed for hot tubs and spas.