What size hot water cylinder do I need in NZ?

A common rule is 45–55 litres per person. So a household of 4 needs a 180–220 litre cylinder. Large families, frequent bathers, or high hot water demand may need 250–300 litres.

Does a hot water cylinder need Healthy Homes compliance?

Healthy Homes Standards do not directly regulate hot water systems in rentals. However, the hot water cylinder must have a functioning pressure relief valve and comply with NZOSHA and plumbing regulations.

What temperature should a hot water cylinder be set to in NZ?

NZS 4305 recommends storing hot water at 60°C minimum to prevent Legionella bacteria growth. Tempering valves are required at point-of-use for showers to limit temperature to 45°C for safety.

Should I get a heat pump hot water system in NZ?

Heat pump water heaters are 3–4× more energy efficient than electric resistance elements and can reduce water heating costs by 60–70%. EECA estimates payback of 3–5 years at current power prices in NZ.

NZ Hot Water Cylinder Sizing Calculator

Calculate the right hot water cylinder size for a NZ home or rental — including Healthy Homes Standards compliance for rental properties.

Hot Water Cylinder Sizing for NZ Plumbers

Sizing a hot water cylinder correctly is one of the most practical jobs a plumber does. Too small and the household runs cold; too large and you're paying to heat water that's never used.

NZ Rule of Thumb

The standard NZ guide is 50–60 litres per person for a mains pressure electric cylinder. This accounts for a daily shower, hand washing, and dishwashing.

Household	Recommended size
1–2 people	135L
2–3 people	180L
3–4 people	250L
4–5 people	300L
6+ people	400L

Healthy Homes Standards for Rentals

Under the Healthy Homes Standards, rental properties must have a hot water system that: - Delivers water at 55°C within 60 seconds at the point of use - Has a thermostat set to at least 60°C (to prevent legionella growth) - Uses a tempering valve to reduce to 55°C at taps

The minimum practical size for a rental is 180L — a 135L cylinder often can't maintain adequate temperature with multiple occupants.

Heat Pump Water Heaters

Heat pump water heaters (e.g. Stiebel Eltron, Reclaim, Rheem) are increasingly popular in NZ. They use 60–70% less electricity than standard electric cylinders. They work best in garages or utility rooms where they can draw heat from ambient air. Allow for noise (similar to a heat pump unit) when selecting location.

Compliance

All hot water work must comply with AS/NZS 3500 (Plumbing and Drainage) and be carried out by a registered plumber. Temperature and pressure relief valves must be installed and discharged safely.