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When an old gas hot water system reaches the end of its life, you have more choices than just swapping in the same thing. The right one depends on your household, your space, your budget, and how you feel about staying on gas. I'm Pete from Water & Gas Worx — a PGDB-registered gasfitter with 17+ years on Auckland tools — and here is a straight look at the options so you can make a good decision rather than a rushed one.
Quick answer: When an old gas hot water system needs replacing, you have three main options: a like-for-like gas storage cylinder, a gas continuous flow (califont) unit, or switching to electric with a heat pump or standard electric cylinder. The right choice depends on household size, space, gas type, and upfront versus running cost. Gas work must be done and certified by a registered gasfitter. Water & Gas Worx quotes before starting — labour is $155+GST for the first hour, then $100+GST per hour.
Option 1: Like-for-Like Gas Storage Cylinder
The simplest option — replace your gas storage cylinder with a new one. It suits households happy on gas who want a familiar, reliable system with minimal change to the setup. Modern units are more efficient than decades-old ones. The trade-off is that you are still storing a tank of hot water and limited by its capacity.
Option 2: Gas Continuous Flow (Califont)
A continuous flow unit heats water on demand, so it never runs out and there is no tank sitting there losing heat. It is wall-mounted and compact, freeing up space. It is a popular upgrade from an old storage cylinder. The trade-offs are a minimum flow needed to fire it up and the need for adequate gas supply. We compare the approaches in hot water cylinder vs continuous flow.
Option 3: Switch to Electric
With New Zealand's long-term direction shifting toward electrification, replacement time is the natural moment to weigh moving off gas — EECA has independent guidance on home energy use. A heat pump hot water system is the most efficient electric option, though it costs more upfront. A standard electric cylinder is cheaper to install but more expensive to run. We cover the bigger picture in is natural gas being phased out in NZ?
What Should Guide Your Choice?
- Household size and hot water habits — heavy, simultaneous use favours continuous flow or a well-sized system
- Space — continuous flow frees up the cupboard a tank occupies
- Upfront vs running cost — cheaper to install is not always cheaper to run
- Gas type — reticulated natural gas vs LPG bottles changes the running cost; see LPG vs natural gas
- Compliance — old external units often need flue clearances brought up to standard, and gas work must be certified; see gas compliance certificates explained
Do Not Wait for It to Fail
Replacing on a planned basis means you can compare options properly and avoid an emergency on a cold morning. If your system is showing its age — rust, dwindling hot water, or simply decades old — it is worth planning ahead.
Gas Hot Water Replacement Across Auckland
Water & Gas Worx are registered gasfitters who replace gas and electric hot water systems across Auckland — we size and recommend the right option for your home and certify the work. See our hot water and gasfitting services and areas we service.
Call 0800 322 322 or email service@wgw.co.nz.
Frequently Asked Questions
Should I replace my gas hot water with the same type or switch?
It depends on your household, space and budget. The options are a like-for-like gas storage cylinder, a gas continuous flow unit, or moving to electric such as a heat pump system. Replacement time is the natural moment to weigh these up. We talk through the trade-offs and size the right solution for your home.
Is continuous flow better than a storage cylinder?
It depends on your needs. Continuous flow never runs out and saves space, but needs a minimum flow to fire and adequate gas supply. A storage cylinder is simpler and handles big simultaneous draws well but is limited by tank size. Neither is universally better — it comes down to your household and setup.
Does replacing a gas hot water system need certification?
Yes. Gas work must be carried out by a registered gasfitter and a Gas Safety Certificate is required. With older external units, the flue clearances often need bringing up to current standards as part of the replacement. We handle the certification as part of the job.
How much does it cost to replace a gas hot water system?
It varies with the type and size of system and the work involved, so we quote before starting. Our labour rate is $155 plus GST for the first hour, then $100 plus GST per hour after that. After-hours is $295 plus GST for the first hour, and public holidays $395 plus GST for the first hour, then $100 plus GST per hour after that.