Water Heater Size Calculator
Determine the right water heater tank size and recovery rate based on occupants, bathrooms, and usage pattern.
How to Use the Water Heater Size Calculator
- Enter the number of occupants.
- Enter the number of bathrooms.
- Select the usage pattern.
- Click Calculate for tank size and recovery rate.
Use Cases
- •New home water heater selection.
- •Replacing an undersized water heater.
- •Rental property plumbing specification.
- •Plumbing contractor estimating.
Formula
Tank size = occupants × factor + bathrooms × 20 L. Factor: low=30, medium=40, high=55 L/person.
Frequently Asked Questions
What is recovery rate?
Recovery rate is how many litres of hot water the heater can produce per hour after the tank is depleted.
What usage pattern should I choose?
Low: occasional use, 1–2 people. Medium: typical family. High: large family with high demand.
Should I choose a tankless heater?
Tankless heaters are efficient for low-demand use but this calculator sizes tank-type heaters only.