Our A/C unit recently took a dive and we bought a unit at Home Depot that sets on the floor and exhausts out the window through a large tube. It has been a life saver until we can get our A/C fixed but it dumps a lot of water so you need somewhere for it to drain. It was so much that I got curious and thought I would measure the water output. Well, this 10,000 BTU unit in the humid East Coast is putting out 8 gallons of water per day! I suspect a roof top unit would do the same. If you could capture this water and add it to your fresh water supply it would be an awesome addition to for dry campers.