I'm in NE Ohio and my 18x36 inground pool always has a solar cover on it when not in use during the summer. I prefer a clear 16 mil cover. It's heavy, but really helps keep the pool warm. I also have a good quality solar reel which makes a world of difference with taking the cover on/off the pool.

My biggest issue is I only get 1-2 years out of a cover. I've tried different thicknesses of covers and different colors (clear, blue). These solar covers are frustrating, but they they really help keep my water about 10 degrees warmer and cut down on evaporation.