Cover on or off - daytime ?

[Spensar]

Heat loss is mainly through evaporation, so IMHO, keeping the cover on or off in the day depends a lot on the weather. If it's a really warm day without much wind, I don't worry about the cover off. If there is a decent wind, or the air temperature is a good amount lower than the water, I leave the cover on.

If it's a day where the pool will be used on and off all day, I leave the cover off regardless, because the pool's there to use, of course.