The amount of water used will depend on your temperature and natural humidity. They are good for getting a higher humidity in arid areas or during winter when all the moisture in the air freezes and falls in the driveway. They also use way less electric than a compressor driven A/C. The water line to a large one is the size of an ice-maker for a fridge, so not much flow. We had a portable one in Arizona (for house cooling). We were off the grid (solar panels and batteries) so only running 1 fairly small motor was nice (pump ran from fan motor). We rolled it over to the kitchen sink and filled it about once a day from the sink sprayer.
Dennis in Montana (temporarily in Florida):hippy: