Field Tool
Landscape Water Use Calculator
What your irrigation costs to run, and what a different system would cost instead.
Irrigation efficiency is the difference between water that reaches a root and water that evaporates, runs off, or lands on the sidewalk. The planting doesn't change. The bill does.
Not sure which is closest? Enter your ZIP in the EPA WaterSense Water Budget Data Finder and match on both peak ET and peak rainfall — not on which city is nearest.
Your rate is on your water bill, or on your provider's rate schedule page. Two things to watch. Many utilities bill in CCF — hundred cubic feet — rather than thousands of gallons; one CCF is 748 gallons, so multiply a CCF rate by 1.34 before entering it here. And most rates are tiered, so use your highest summer tier rather than the base rate, because irrigation is what pushes you into it. Leave out fixed service charges — those don't change with how much you water.
Fill in every field to see the estimate.
These are operating figures for an established landscape — year three onward, after a standard two-year establishment period. Establishment watering is a different problem with different math: it is scheduled per plant at the root ball, not spread across an area, and it assumes no help from rainfall. Nothing on this page should be used to size pipe, valves, a meter, or a controller.
These are irrigation-season figures, not year-round ones. The federal source counts only the months when the landscape actually needs watering — roughly March through October in this climate — and already subtracts the rainfall a location typically gets. Nobody waters in January and the numbers don't assume anyone does. One consequence worth remembering: don't divide the annual figure by twelve to get a monthly bill. The water is spent across about seven months, not spread evenly over the year.
One more thing this can't see: it estimates what the landscape needs, not what your controller does. A system running in early March and late October because the schedule says so, rather than because the plants are asking, is spending water these figures never counted.
Water rate is held flat across the ten-year figure. Rates generally rise, so treat the projection as conservative. Most utilities also bill outdoor water in tiers, meaning heavy summer irrigation is charged above the average rate — the real bill on a high-use landscape will run higher than shown.
Efficiency ratings assume the system is maintained and correctly scheduled. A drip system with clogged emitters and a controller nobody has touched since installation is not an 85 percent system.
This is a planning estimate, not a measurement. The source method carries a wide range of possible answers and is no substitute for a meter or an irrigation audit.
Irrigation factors and system efficiencies: Federal Energy Management Program, Guidelines for Estimating Unmetered Landscaping Water Use, PNNL-19498, July 2010, Tables 3, 5 and 6 and Section 2.6.