Safety cover solar heating, open or closed

[bobby1017]

I asked this in my construction thread but this may be a more appropriate place...

With an auto safety cover, will the pool warm more in the sun with the cover open or closed? The cover is a dark blue.

 

[mikespoolfl]

Only where the cover is in contact with the water would there be a small amount of heat transfer. The effect of the dark cover would be like a car with heavy tinted windows vs a car with non tinted sitting in the sun. Leave cover open.