Last updated October 2026
A gas califont heats water as it flows, so the shower never runs cold halfway through. In Nelson and Tasman, where home gas comes from LPG bottles rather than a pipeline, there are a few extra things to think about before choosing one. This guide covers how califonts work, how to size one, the running cost question, and who can install it.
★View the Best Plumbers in Nelson→What a gas califont is
“Califont” is the everyday New Zealand name for a continuous flow gas water heater, sometimes called instant or tankless hot water. There is no storage tank. When you turn on a hot tap, water flows through the unit, a burner lights, and the water is heated on its way to the tap. Turn the tap off and the burner stops.
That gives califonts their two main advantages: hot water that does not run out while there is gas and water, and no cylinder taking up a cupboard.
Gas in Nelson and Tasman means LPG
New Zealand’s natural gas pipeline network is in the North Island, so homes in Nelson and Tasman that use gas run on LPG. For a califont that usually means a pair of 45 kg bottles outside with an automatic changeover valve, so the supply switches to the full bottle when one runs empty.
A few practical points follow from that:
- Placement of the bottles. They need a safe, ventilated outdoor spot with access for the delivery truck, and set distances from windows, doors and drains.
- Pipework. The gas line from the bottles to the califont is gasfitting work, and so is any change to it.
- Ordering. With two bottles and a changeover valve, you swap one while still running on the other. Without one, running out means no hot water.
How to size a califont
Califonts are sized by flow rate, in litres per minute, rather than by tank volume. The question is how many hot taps and showers will run at once.
One bathroom, one or two people
- Typical use at once
- One shower or tap at a time
- Size to discuss
- Smaller unit
One to two bathrooms, a family
- Typical use at once
- A shower plus the kitchen tap
- Size to discuss
- Mid-size unit
Two or more bathrooms
- Typical use at once
- Two showers at the same time
- Size to discuss
- Larger unit
Treat this as a starting point for a conversation with the installer. Water pressure, the length of the pipe run and how hot the incoming water is in winter all affect the result. An undersized unit is the most common complaint: the shower goes lukewarm when someone turns on another tap.
Inside or outside?
Most califonts in Nelson are mounted on an outside wall. An external unit needs no flue and is the simpler install. An internal unit needs a flue to take combustion gases outside, and installation rules on clearances and ventilation are stricter.
Most modern units also need a power point for the electronics and temperature controller, so plan for that if the wall has no outdoor socket.
Running cost: califont, cylinder or heat pump
This is the question most people really want answered.
- Califont on LPG. No standby heat loss, because nothing is stored. You pay for gas only when hot water is used.
- Electric cylinder. Simple and reliable, but it keeps a tank of water hot around the clock.
- Heat pump cylinder. Uses the least energy of the three. The Energy Efficiency and Conservation Authority’s guide to hot water heat pumps estimates running costs around 75 percent lower than LPG water heating.
So a califont is rarely the cheapest option to run on bottled gas. Where it wins is endless hot water, space, and suitability for places like baches, sleepouts, and homes that already have LPG for cooking or a gas fire.
Temperature and safety
Califonts are usually set to deliver water at a fixed temperature through a controller, which helps avoid scalding. The Building Code also limits how hot water at basins, baths and showers can be. A gasfitter should set the unit correctly at installation and show you how the controller works.
Have a califont serviced periodically, particularly if you notice yellow flames, soot marks, a smell of gas, or water temperature that swings while a tap runs.
Who can install a califont
Installing a califont or altering its gas supply is gasfitting, which is restricted work in New Zealand. It must be done or supervised by a licensed gasfitter, and you should receive a certificate of compliance for the gasfitting work. If the califont also replaces a hot water cylinder, the plumbing side needs an authorised plumber too.
You can confirm anyone’s licence on the public register of the Plumbers, Gasfitters and Drainlayers Board before you book.
Questions to ask before you book
- What flow rate do you recommend for this house, and why?
- Where would the unit and the gas bottles go?
- Is an automatic changeover valve included?
- Does the quote include the power supply, the gas pipework and the certificate of compliance?
- How often should it be serviced?
Getting started with gas hot water in Nelson
Plumbing and More is a family-run plumbing, gasfitting and drainlaying business in Nelson and Tasman. Its gas fitting work covers domestic and commercial gas servicing, maintenance and new builds, and the team also handles hot water cylinder replacements and upgrades, which helps when you are weighing up a califont against a cylinder or heat pump. You can contact Plumbing and More or call 021 758 651.
