Quote Originally Posted by tphaggerty
Brian,

"Solar" cover is a misnomer. Most of the heat savings from a "solar" cover involve stopping evaporation, which sucks heat from water like nothing else. Solar covers do very little to actually add heat to the water. In fact, most of the solar covers that claim they heat the water are clear, they are allowing the sunlight to enter and heat the water directly.
This is right on target - a solar cover really should be called "Evaporation Inhibitor" - but hey - it's hard to market something under that name.

Keep your cover on at night, and off when A) When the air temp is above the water temp and/or B) when there is sufficient sunlight hitting the pool.

I have tested many times to see which is better. Everytime, no cover during the day (from noon-sundown) yields much higher temperature rises. Put the cover back on after sundown to retain that heat gain.

On the other side of the coin - keeping the cover on whenever not in use will usually maintain a comforatble swimming temperature for me, and it also does reduce dirt/debri in the pool as well as reduce chlorine usage. My problem with the cover on all the time insects and frogs. They tend to get under the cover around the edges, and of course can't get swept into the skimmer. So when I go to remove the cover to swim, I'm fishing out 2 or 3 dead frogs and hundreds of beetles and other bugs. These insects and frogs also contribute to increased Cl usage for me.

Good luck!