Arizona has extremely hot summers that require constant air conditioning. When the evaporator coil cools down, water condenses on the coils and falls into a pan. The pan flows into a PVC pipe that is usually routed to the base of the outside of your house. This water slowly drips at the base of your house, potentially damaging your foundation. It may not seem like a lot of water, until you start harvesting it. I can typically harvest 2 gallons per day from June through September.
Since my condensation drip outlet comes out low to the ground and right in front of a walkway, I made a custom collection bucket for harvesting the water. The 10 gallon buckt is as big as I could fit without impeding the walkway. I added a wooden lid with a bug screen to allow water to flow in to the bucket, but prevent mosquitoes from breeding in the water. The lid also helps to prevent evaporation. Since the screen is flexible, I can turn up the lid and lean it against the house while accessing the water, then turn it back down when I am done. My condensation drip outlet had very little clearance to my stucco walls, so I used a plastic bib to ensure that the water would flow into the bucket and not down the wall.
This water is clean and soft (lacking dissolved minerals), because it was formed by condensation. This makes it particularly good for watering plants. The tap water in Arizona is exceptionally hard and can lead to salt deposits in your garden soil.
If your condensation drip outlet is higher up, you may be able to route the water into a rain barrel. If the area is unobstructed by a walkway or other structure, you may want to consider directly routing it using PVC pipe to a basin. However, you need to think this through. You don’t want ugly PVC pipe above ground. If you glue the PVC pipe it is permanent. Most desert plants do not like to be constantly kept moist, as they will die of root rot.