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Upgrading your hot water system? The two most popular options in New Zealand are traditional storage cylinders and continuous flow (instant) systems. Here's an honest comparison from Pete at Water & Gas Worx — PGDB-registered with 17+ years on Auckland tools and dual-certified for plumbing and gasfitting — to help you choose.
Quick answer: Storage cylinders cost $2,499–$3,500 installed (electric like-for-like), are simple and proven, but can run out of hot water and lose energy 24/7. Continuous flow (e.g. Rinnai Infinity, Rheem Metro) costs $3,599–$5,500 installed, gives unlimited hot water, has a longer 20+ year lifespan, and lower running costs — but needs a gas connection. For larger households or homes that keep running out, continuous flow wins long-term. Water & Gas Worx labour is $155+GST first hour, $100+GST per hour after, with Gas Compliance Certificates included on every gas job.
How They Work
Storage Cylinder
Heats a tank of water (typically 135 to 300 litres) and keeps it hot until you need it. Powered by electricity, gas, or a heat pump.
Continuous Flow
Heats water on demand as it passes through a wall-mounted unit. No tank — fires up when you turn on a hot tap, shuts off when you stop. Most run on natural gas or LPG, requiring a certified gas fitter for installation.
Pros and Cons
Storage Cylinder
Pros:
- Lower upfront cost
- Simple, proven technology
- Works with existing connections
- Available in a wide range of sizes
- Can pair with solar panels or heat pumps
Cons:
- Can run out of hot water
- Takes up cupboard space
- Standby heat loss — uses energy 24/7
- Limited lifespan (15 to 20 years)
Continuous Flow
Pros:
- Unlimited hot water — never runs out
- Compact wall-mounted unit saves space
- No standby energy loss
- Longer lifespan (20+ years)
- Lower running costs vs electric cylinders
Cons:
- Higher upfront cost
- Requires gas supply
- Flow rate limits simultaneous taps
- Needs electrician + plumber + gasfitter — all work requires a gas compliance certificate
Cost Comparison
Rough guide for Auckland installations (2025/2026 pricing):
| System | Installed Cost |
|---|---|
| Electric storage cylinder (like-for-like) | $2,499 - $3,500 |
| Gas storage cylinder (Vulcan, Rheem) | $2,800 - $4,200 |
| Gas continuous flow (e.g. Rinnai Infinity, Rheem Metro) | $3,599 - $5,500 |
| Heat pump hot water | $6,399 - $8,299 |
Running costs vary, but continuous flow gas systems typically cost less per year than electric cylinders, especially for larger households. The Energy Efficiency and Conservation Authority (EECA) provides detailed running cost comparisons. See our pricing page for installation costs.
Which Is Right for You?
Choose a storage cylinder if:
- You want the lowest upfront cost
- You already have a cylinder cupboard and electrical connection — check for emergency plumber options if yours fails unexpectedly
- Your household is small to medium (1 to 3 people)
- You want a straightforward like-for-like replacement
Choose continuous flow if:
- You're sick of running out of hot water
- You have a gas connection (or are willing to install one)
- You want lower long-term running costs
- You have a larger household or high hot water demand
- You want to free up cupboard space
Frequently Asked Questions
Is continuous flow better than a hot water cylinder?
It depends on your household. Continuous flow gives you unlimited hot water and lower running costs, but has a higher upfront price and needs a gas supply. A cylinder is simpler and cheaper to install. For larger households that keep running out of hot water, continuous flow is usually the better long-term choice.
How much does a continuous flow system cost to install?
A gas continuous flow system like the Rinnai Infinity typically costs between $3,599 and $5,500 fully installed in Auckland. The exact price depends on your existing gas and water connections and the size of the unit you need.
Can I switch from a cylinder to continuous flow?
Yes, but it is not a direct swap. You will need a gas supply run to the unit location, new water connections, flue work, and electrical for the controller. A qualified plumber and gas fitter can assess your setup and give you a quote for the full changeover.
