Garden Irrigation water cost calculator
An inch of water over 1,000 square feet is 623 gallons. Applied weekly across a decent-sized lawn through a dry season, that adds up to a number most people have never worked out, and it is usually the largest single line on a summer water bill.
How this is calculated
Gallons = area (sq ft) × depth (in) × 0.623, since one inch over one square foot is 0.623 gallons. Cost = gallons ÷ 1,000 × your rate, doubled if sewer is billed on the same volume.
Worth knowing: Many utilities bill sewer charges on total metered water, so irrigation you never send down a drain is charged twice — a separate irrigation meter often pays for itself where that applies, and it is worth ringing your utility to ask. Tiered rate structures also mean summer irrigation can push you into a higher band, so the marginal cost may exceed your average rate.
Common questions
How much water is an inch?
About 623 gallons per 1,000 square feet. A 5,000 square foot lawn getting an inch a week is drinking roughly 3,100 gallons every week through the season.
Where does the 25% saving come from?
It is a conservative figure for what better scheduling typically recovers — a rain sensor that skips cycles after storms, watering early morning instead of midday, and correcting run times to match a measured precipitation rate. The EPA WaterSense programme cites savings in that range from controller upgrades alone.
Am I charged sewer on water I put on the lawn?
In many places, yes — sewer is billed on total metered water regardless of where it went. Some utilities offer a separate irrigation meter or a summer averaging scheme. It is worth asking, because on a big lawn it doubles the cost of every gallon.
Affiliate Disclosure
Some links on this page are affiliate links. As an Amazon Associate, we earn from qualifying purchases — at no extra cost to you. We do not buy, test, or physically handle the products we cover; our rankings come from aggregated owner reviews, ratings and expert consensus. Commissions never change our verdicts. How we rank · full disclosure.