A solar pool cover will help raise your pool water to a higher temperature during the day when the sun is out. At night it will help hold some of the heat in the pool water that is normally lost when outside temperatures drop. Overall, this will reduce the amount of energy you use to heat your pool water, lowering your cost of pool ownership. If you don't have a pool water heater, it will help to heat your pool above the temperature it would normally reach on a warm day. A fringe benefit is that the cover will also help keep the pool water clean, preventing some dirt / debris from entering the pool. There many great reasons to use a solar pool cover. It can reduce stress on the pool heater, It can keep more heat in the pool, especially when the sunsets at night.