A pool is comfortable in Florida for maybe half the year without help. Heating it with an electric resistance heater or a gas heater is the most expensive way to extend that season. Solar pool heating is the cheapest, because the water itself is the storage medium and the collectors are unglazed, which makes them far less expensive per square foot than photovoltaic panels.
Your existing pool pump pushes water through an array of collectors on the roof. The water picks up heat and returns to the pool. An automatic controller compares roof temperature to water temperature and diverts flow only when there is useful heat available, so the system never cools the pool by running at the wrong time.
Filtration is a large year-round load in its own right. A variable-speed pump run at low speed for longer periods filters better and uses a fraction of the energy of a single-speed pump, which is why Florida code has pushed the industry that way. Where a pool is heated by a heat pump rather than solar, correct sizing and a pool cover matter more than the equipment brand.
Roof-mounted collectors are a permitted installation and, in High-Velocity Hurricane Zone counties, need product approval and engineered attachment. Collectors are drained and the array is designed so that panels and headers can withstand rated wind loads. Pool equipment changes involving electrical work require an electrical permit and bonding to current code, which is frequently found deficient on older pools.
Most customers combine two or more of these in a single project.
Short answer: Modern pool systems use variable-speed pumps, smart scheduling, and automation to run only as much as needed instead of at full power all day, cutting energy waste while maintaining performance.