Just changed out a Duo-therm 13.5 btu for a 15 btu last week on our 2008 Georgetown. Both A/Cs were 13.5 btu units, and the one in the back would run, but would not cool. A mobile RV company checked it and said low on Freon and couldn't be charged so I paid the difference on warranty and upgraded to a 15 btu Duo-therm. Also paid to swap the good front 13.5 unit to the rear and put the new 15 btu unit on the front. Hasn't been real hot yet, so can't say if it cools better as both the old 13.5 btu and 15 btu units have air coming in a 40 degrees when 80 degrees outside. Perhaps will notice the difference when it gets hotter. One difference noticeable is the outside appearance where the box over the unit is smaller on top of the MH. Also, the newer unit is a little quieter. Thought it would be better to have the bigger A/C on the front if we had to use while driving down the road on a hot day.