Quick Answer — How Much Water Does Xeriscaping Save?
Landscape water use is not a fixed number per square foot. It follows the formula water agencies use for landscape budgets:
Gallons per year = ETo × plant factor × area × 0.62 ÷ irrigation efficiency
ETo is reference evapotranspiration in inches per year — how much water a reference surface loses to evaporation and plant use in your climate. The 0.62 converts inches over a square foot into gallons. The plant factor is what actually changes when turf becomes xeriscape: cool-season turf sits near 0.8, a low-water planting near 0.2 to 0.3.
Take 1,200 sq ft of lawn in a climate with 52 inches of annual ETo, currently on 65%-efficient spray irrigation, replaced with a 0.25 plant factor xeriscape on 85%-efficient drip:
- Lawn — 52 × 0.8 × 1,200 × 0.62 ÷ 0.65 = 47,616 gallons a year, or 39.7 gallons per square foot
- Xeriscape — 52 × 0.25 × 1,200 × 0.62 ÷ 0.85 = 11,379 gallons a year, or 9.5 per square foot
- Saved — 36,237 gallons a year, a 76.1% reduction
That is the equivalent of about 2,107 showers or 906 bathtubs of water a year, from one lawn.