Pool covers, also known as pool blankets or solar covers, are used to keep heat in a swimming pool. At night or during cool weather, pool heat is lost to the ambient air through evaporation and radiation. Keeping this heat in the pool is the job of a pool cover, regardless of the heat source. By drastically reducing evaporation, pool covers help you retain heat. Since heated pools evaporate faster than unheated pools, a pool cover is an effective means of keeping the heat in.
Pools in Florida are heated four primary ways — natural heating from the sun warming the pool each day, solar pool heating using purpose-built solar thermal panels, electric heating using a heat pump, or gas heating with natural gas or propane. Regardless of the heat source, covering your pool will result in higher average temperatures every day of the year, and will make your heater work better. Using a pool cover alone will not contribute much to the actual heating of the pool, but heat will be retained better. If you heat your pool with solar energy, not as much heat will be lost each night, and you will achieve higher ultimate temperatures each day. Your pool will also reach desired temperatures faster. If you use a heat pump or gas heater, not using a pool cover is like using air conditioning with your doors open. Ultimately all of the money you spend heating your pool will be lost to the outside air. During the most challenging weather, electric heat pumps will not be able to keep up with the loss of heat from an uncovered pool.
That is why solar pool heating is so desirable in Florida. Many people do not want to cover their pool because of the inconvenience and danger that covered pools present. At least with solar pool heating you are not paying daily operational costs, so the heat you lose technically does not cost anything. If you choose to cover your solar heated pool you will gain up to 5º F of additional heat, so it is definitely advisable for maximum performance, but it is certainly not required. Solar heated pools will heat your pool every day of the year without covering it. If you want to extend your swimming season to the maximum extent possible, a pool cover will help. A cover is most helpful when nighttime temperatures dip very low relative to pool temperatures.
You are not required to cover your Florida pool when using a solar pool heater, but doing so will increase your enjoyment and provide maximum comfort.