Interactive core module
Rainwater capture estimator
Set a roof area, a rainfall level and a collection efficiency to model an annual capture range, seasonal variability and overflow likelihood. The chain is the same one used in the tank-sizing module.
This is an educational estimation model only and not a guarantee. It applies generic coefficients to illustrate how the variables interact — it does not measure, size or certify any real system, and it is not engineering, plumbing or design advice.
Inputs
Adjust all three to generate a result.
Model: capture ≈ area × rainfall × runoff (0.8) × efficiency. 1 mm on 1 m² ≈ 1 litre.
How to read the output
Capture range
A median annual figure with a dry-year to wet-year band, because rainfall varies year to year well beyond its average.
Seasonal variability
How the modelled inflow is spread across the seasons — the peakier the profile, the more storage must buffer dry gaps.
Overflow likelihood
A qualitative read on how often peak inflow is likely to exceed typical storage, rising with roof area and peaky rainfall.
Every output is indicative and generic. A real assessment uses local rainfall records, your actual roof and system, and current regulations — none of which this model contains.