But now you have to carry extra 15 gals of water just for the cooler.
Agreed. After further research I found it uses around a gallon an hour during the hot days. I don't have room for a larger tank unless I change my floor layout and run water lines to the roof, its a little late for that.
There are some reviews on RV forums. Apparently it works as good or a little better than a 15k AC unit on way less power. Cost is around the same as an AC unit. If water is not a concern, you live in a dry area and you are short on power it could be a viable option.