Swimming pool heating costs can be significantly reduced by using a pool cover.

Use of a pool cover also can help reduce the amount of chemicals (chlorine, etc.) required by the pool. Outdoor pools gain heat from the sun, absorbing 75–85% of the solar energy striking the pool surface. Though a cover decreases the total amount of solar heat absorbed by the pool, the cover eliminates heat loss due to evaporation and reduces heat loss at night through its insulating properties. Most swimming pool heat loss is through evaporation.

The heating effectiveness of a cover depends on type. A transparent bubble cover is the most effective, as it allows the largest amount of solar flux into the pool itself. Thermal bubble covers are lightweight UV-stabilized floating covers designed to minimize heat loss on heated swimming pools. Typically they are only fitted in spring and fall (autumn) when the temperature difference between pool water and air temperature is greatest. When used consistently they can raise average pool temperatures of an outdoor pool by around 18 °Fahrenheit (11 °Celsius) when combined with a well sized solar pool heating system, or about 11° Fahrenheit (6 °Celsius) without a solar heater but with full sun exposure.

Bubble covers are typically applied and removed by being rolled up on a device fitted to one side of the pool (see illustration). Covers often fall apart after four or five years due to sun exposure, overheating in the sun while off the pool, and chlorine attacking the plastic. Bubble covers should be removed during super chlorination.