Rainwater System ROI Calculator
Plug in what you spent (or plan to spend) on a rainwater system, your water price, and how much you collect each year to see the payback.
Annual savings = (gallons collected ÷ 1,000) × water price. Water price is an illustrative combined water+sewer rate; enter your bill's rate for accuracy. Payback ignores maintenance, pump, and rising water rates, so treat it as a planning estimate, not a guarantee.
Water price source: Illustrative typical combined water+sewer residential rates (USD per 1,000 gal), rounded. Derived from public utility rate surveys (USGS Estimated Use of Water, Circle of Blue). Verify on your bill; intra-state variation is large.
Related: Tank sizing calculator → · Garden watering needs →
Frequently asked questions
Why does my water price matter so much?
Payback = system cost ÷ annual savings, and savings = gallons collected × price per 1,000 gal. In high-rate cities a small barrel can pay back in a few years; in cheap-water areas the same barrel may take a decade. Always enter your real bill rate.
What costs should I include?
Count the barrel or cistern, gutters/diverters, screen, pump if any, and installation. The calculator uses one up-front cost and ignores maintenance and rising rates, so it is a planning estimate rather than a guarantee.
Does this count rainwater rebates?
No. Many utilities and some states offer rain barrel rebates that shorten payback; subtract any rebate from your system cost before calculating for a true number.