Why it exists
Most rainwater tank calculators in New Zealand are run by a tank manufacturer, and they size for the manufacturer's own range. This one is independent: it is not tied to selling anything, and the size it recommends is the size its model says your household needs, not the size a catalogue happens to stock.
How the calculation works
In brief: the calculator works out your household's daily water demand from a set of usage figures, then simulates a year of inflow against that demand, using your roof area and your region's rainfall, to find the smallest tank that does not run dry. The full reasoning, every figure it uses, and the model's limitations are on the methodology page.
Who built it
Built by Iceni Web Design.