The water temperature you desire for your swimming pool not only affects the size of the pool's heater, but also your heating costs if use a gas or heat pump pool heater.
Pool water temperatures typically range from 78ºF to 82ºF. The American Red Cross recommends a temperature of 78ºF for competitive swimming. This coincides with good fuel savings. However, this may be too cool for young children and the elderly, who may require a temperature of 80ºF or higher.
The energy consumption for each degree rise in temperature will cost 10%–30% more in energy costs, depending on your location. In warmer climates, this percentage is higher because of the relatively low cost of heating a pool at 78ºF.
On the following pages, see the tables showing the costs of heating pools at different temperatures in different U.S. cities:
Also, turn the temperature down or turn off the heater whenever the pool won't be used for several days. This will save energy and money. It's a myth that it takes more energy to heat a pool back up to a desired temperature than you save by lowering the temperature or turning off the heater.