I sympathize with you on your cool pool. Here in NW Oregon our pool is 75 deg. We rely on solar panels on the roof of the house but you need sun for that to help.

I leave my Polaris in with the cover on all the time with no problem. Of course with the cover on there is less for him to do (we named him Robbie after the TV robot) because the debris stays on top of the cover. Not only will you save heat but you will save water loss caused by evaporation.