The amount of water used by your Xeriscape will depend upon the size of your landscape, the plants you select, your watering habits, the local climate, soil, wind, and any number of additional factors. While it is impossible to predict the impacts of converting to Xeriscape for the individual, there are a number of research studies that have shown that substantial water savings that can be achieved by converting turf grass to Xeriscape.
A five year study of homes that converted turf to Xeriscape in Las Vegas, Nevada found a 33 percent reduction in average monthly water use and a 39 percent reduction in average summer monthly water use resulting from the Xeriscapes (Sovocool and Rosales, 2001). This study also found that conversion to Xeriscape reduced annual maintenance costs by one third on top of the water savings.
Keep in mind that Xeriscape, like all landscapes, takes time to establish. During the first few years, new plants often require more water than do mature plants with established and deep root systems. This is why it is important to evaluate the water use of Xeriscapes over a long period of time and not just during the first or second year after installation.
To search for more research on Xeriscape, visit WaterWiser.
Kent A. Sovocool and Janet L. Rosales. 2001. A Five-Year Investigation into the Potential Water and Monetary Savings of Residential Xeriscape in the Mojave Desert. Proceedings of the 2001 AWWA Annual Conference, Washington D.C.