...of water in the desert air, apparently.
The caretaker of my building in Cairo directs the water that condenses in all of the air-conditioner units in the building into the gardens. While it isn't energy efficient AT ALL, I am always surprised by how much water gets to the garden. And as the weather gets hotter, the residents use their air-con more meaning more water for the garden. Again, it's not energy efficient in any way, but it does save water by reclaiming it from the air, and quite a lot of it.