Rainwater Harvesting Payback Calculator
Estimate annual rainwater collection, usable yield, water-bill savings, net annual benefit and simple system payback.
Default project preview
62.4 years
Annual captured water
32,296 gal
Annual usable water
22,607 gal
Gross annual water savings
$192.16
Net annual benefit
$72.16
Calculator
Build the material order
Your order will appear here
Enter the project details and calculate a rounded material estimate.
Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Captured water = roof area × rainfall × runoff efficiency. Usable water applies the utilization fraction. Net annual benefit = avoided water cost − maintenance. Simple payback = net upfront cost ÷ net annual benefit.
BuildMeter Guides
Understand the measurements and assumptions
Use these visible reference guides before changing project inputs or planning allowances.
FAQ
Rainwater Harvesting Payback Calculator questions
Why is usable water lower than captured water?+
Storage overflow, seasonal mismatch and limited non-potable demand can prevent all collected water from being used.
Does the calculator size the storage tank?+
No. It estimates annual yield and economics. Tank sizing needs rainfall timing, demand timing and desired reliability.
What happens when maintenance exceeds savings?+
The calculator reports no positive simple payback because the entered annual net benefit is zero or negative.