WaterCalcLabRainwater ROI Calculator
Estimate simple annual payback using eligible annual demand and actually available annual supply.
Your result
Bars compare only results in the same unit group. They are normalized, not a time-series forecast.
Planning result based on your inputs.
How this tool works
Estimate simple annual payback using eligible annual demand and actually available annual supply.
net savings = displaced m³ × tariff − maintenance − kWh × energy price; payback = capital/net savingsExample calculation
The prefilled form is a worked example. Its base-unit inputs and expected outputs are shown below; use the reset button to restore it.
| Input | Example |
|---|---|
| Available supply in the same period | 15000 |
| Demand in the same period | 20000 |
| Avoidable volumetric price | 3 |
| Initial investment | 2000 |
| Annual maintenance | 50 |
| Annual energy use | 40 |
| Electricity price per kWh | 0.3 |
Frequently asked questions
How should I choose the inputs?
Use measurements and local records for the stated period. All preset values are illustrative examples, not recommendations.
What does this result leave out?
Not a financial return guarantee. Excludes financing, discounting, tariff changes, replacements and residual value. Non-positive net savings have no finite payback.
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Method version 1.0 · Last reviewed: 2026-10-10