A third of
your bill is
hot water.
A standard electric cylinder heats water the same way a jug does — it turns a unit of electricity into a unit of heat, and that is the ceiling on how efficient it can ever be.
A hot water heat pump doesn't make heat. It collects heat that is already in the outside air and moves it into your cylinder, using a compressor and refrigerant to do it. Because moving heat costs far less energy than creating it, the same tank of hot water arrives for a fraction of the power — EECA puts it at 60–75% less electricity than a conventional electric cylinder.
For running costs, EECA's national comparison puts a hot water heat pump at roughly $180 a year against roughly $480 for a standard electric cylinder. That is modelling for an average New Zealand household, not a quote for your house — what you actually save depends on how much hot water you use, how old your current cylinder is, and what you're paying per unit.
The case is strongest if your cylinder is already near the end of its life. Nearly half of New Zealand's electric cylinders are more than ten years old. If yours is on borrowed time, the choice isn't really “heat pump or keep what I've got” — it's what you replace it with.
Not sure whether it stacks up for your place? We'll look at your cylinder, your hot water habits and where the unit would have to sit — then tell you straight whether it's worth it.
Heat moved,
not manufactured.
The same technology as the heat pump on your wall, pointed at a cylinder of water instead of a room. Most units sold here are all-in-one — compressor and tank in a single outdoor unit.
Draws in air
A fan pulls outside air across an evaporator coil. Even cold air holds usable heat — far more than most people expect.
Concentrates it
Refrigerant absorbs that heat and a compressor squeezes it, which raises its temperature well above the air it came from.
Heats the cylinder
That heat transfers into the water in the tank. The refrigerant cools, expands, and starts the loop again.
Boosts when needed
A built-in electric element covers the coldest nights and heavy demand, so you never run out — it simply isn't doing the work most of the time.
“Will it work
down here?”
It's the first thing everyone asks, and it deserves a straight answer rather than a brochure figure.
Yes — but the unit has to be chosen for Dunedin, not for Auckland.
Dunedin's average July overnight low is 3°C — well inside the operating range of every unit we install. For most of the year, a hot water heat pump here performs much as it would anywhere else in the country.
Winter is where the detail matters. The efficiency figures on a spec sheet are measured at around 20°C, so they aren't what you get on a frosty morning — the colder the air, the harder the unit works for the same tank of water. Below its rated minimum it hands over to the built-in electric element until things warm up. That's designed behaviour, not a fault. But with around 58 frost days a year here, a unit rated to −7°C and one rated to −10°C are not the same purchase.
So two things decide whether this works for you: a unit with the right cold-weather rating, and somewhere sheltered to put it with decent airflow — not a shaded corner or a sealed-up garage. Get both right and winter is a manageable dip. Get them wrong and you've bought an expensive electric cylinder.
We won't quote you a laboratory efficiency figure and let you assume it applies in July. We'll tell you what the unit is rated to, where it needs to sit, and what that means on your coldest mornings.
Your cylinder is
probably on ripple
control.
Aurora Energy — the lines company for Dunedin — can switch hot water cylinders off during peak demand, usually for two to three hours at a time through the colder months. Households on that arrangement get a reduced line charge for the inconvenience.
Here's the catch. A hot water heat pump doesn't necessarily sit on that control circuit the way a resistance element does. Swap one for the other without thinking it through and you can quietly lose the tariff arrangement you were on — and find out about it a bill or two later.
It's a small thing that is genuinely easy to get wrong, and it's the kind of detail a supplier from out of town won't think to raise. We work out how your unit should be controlled and scheduled as part of the job, before anything gets disconnected.
Three brands,
chosen on merit.
We supply and install Gree, Carrier and Panasonic hot water heat pumps. Which one suits you comes down to household size, where the unit can sit, and how cold that position gets.
Gree
The WHIO range is an integrated unit — compressor and cylinder in one outdoor package, so there's no indoor tank to find room for. A straightforward, well-priced swap for a standard electric cylinder.
Carrier
The Carrier Blue is another integrated unit, with a larger backup element and a low noise rating — worth knowing if the only sensible position is near a bedroom window or close to a neighbour's boundary.
Panasonic
The CO₂ unit uses carbon dioxide as its refrigerant rather than a synthetic one, runs very quietly, and carries the lowest cold-weather rating of the three. In a Dunedin winter, that last point is not a small thing.
Specifications are manufacturer-stated for units sold in New Zealand and can change between model years. We'll confirm the exact model, capacity and warranty in writing before you commit to anything.
Bigger than the
cylinder you've
got now.
A heat pump refills a cylinder more gently than an element does. That's what makes it efficient — and it's also why sizing it like-for-like is a mistake.
If the tank is too small for the household, a run of back-to-back showers drains it faster than the compressor can recover, and the electric element steps in to catch up. That works — you won't run cold — but every time it happens you're paying resistance-heating prices again. Going one size up is usually the cheapest efficiency you'll ever buy.
| Household | Typical cylinder size | Notes |
|---|---|---|
| 1–2 people | Around 180L | Comfortable for a couple or a single-person household with normal usage. |
| 3–4 people | Around 270L | The most common fit for a New Zealand family home, and the size we install most often. |
| 4–6 people | 300L or more | Also the right call for smaller households with heavy demand — long showers, a bath most nights, or a spa. |
A useful rule of thumb is roughly 50 litres per person per day. We'll size yours on what your household actually uses, not the average.
Against the
alternatives.
We install hot water heat pumps and solar hot water, so we've got no reason to steer you toward either one. Here's how the three realistic options compare for a Dunedin home.
| Electric cylinder | Hot water heat pump | Solar hot water | |
|---|---|---|---|
| Running cost | Highest — around $480/yr on EECA's national modelling | Lowest year-round — around $180/yr on the same modelling | Very low when the sun is on the collectors; backup element covers the rest |
| Upfront cost | Lowest — EECA puts it around $4,000 installed | EECA puts it around $7,000 installed | Typically the highest of the three |
| Works at night | Yes | Yes | No — stored heat only, then backup |
| Affected by Dunedin winter | No | Yes — efficiency dips in cold air; element covers the coldest nights | Yes — shorter days and more cloud mean more backup heating |
| Roof work required | No | No | Yes — roof-mounted collectors |
| Typical life | Varies by cylinder | Around 15 years (EECA) | Long collector life; cylinder and backup serviced separately |
Cost figures are EECA's national averages, published for guidance. They are not a quote, and they don't account for Dunedin electricity prices or the state of your existing installation. Read about solar hot water →
The rules
changed in
2024.
Hot water is one of the more heavily regulated parts of a house, for good reason. Here's what a compliant installation actually involves.
The Building Code requires water to be stored at a minimum of 60°C to control Legionella, but delivered to showers and bathroom taps at no more than 50°C to prevent scalding — reduced from 55°C on 1 November 2024. That gap is bridged by a tempering valve, which is now mandatory on new and replacement systems.
Replacing an existing storage water heater with a heat pump in the same position is exempt from building consent under Schedule 1 of the Building Act, provided the work is carried out or supervised by a registered certifying plumber. New builds, or moving the cylinder to a new position, are treated differently — we'll tell you which applies before we start.
The electrical side must be done by a Licensed Electrical Worker registered with the EWRB, and a Certificate of Compliance issued within five working days. That's our own trade — Serviceman has been a registered electrical contractor in Dunedin since 1986, and every job we do is covered by the $20,000 Master Electricians Guarantee.
Cylinders must be restrained against earthquake movement under Building Code clause B1. It's routine work, but it is not optional, and it's one of the things a cut-price installation quietly skips.
One more thing worth saying plainly: there is no government grant for hot water heat pumps. Warmer Kiwi Homes covers insulation and high-wall space heating heat pumps only. If anyone tells you a subsidy is available for hot water, check it before you sign.
Questions we
get asked.
If your question isn't here, call us on 03 455 3333 or use the form below.
Will a hot water heat pump actually work through a Dunedin winter?
Yes. Dunedin's mean overnight low in July — the coldest month — is 3°C (NIWA, 1991–2020 reference period), which sits comfortably inside the operating range of every unit we install. The honest detail most suppliers leave out is what happens on frost nights: Dunedin averages around 58 frost days a year, and as the air gets colder a heat pump has less heat to draw on, so it works harder for the same result. Below its rated minimum the unit falls back to a built-in electric element until the air warms up. That is designed behaviour, not a fault. It is also exactly why unit selection matters more here than it does in Auckland, and why we size and site the outdoor unit for Dunedin conditions rather than fitting whatever is in the van.
How much will it actually cut off my power bill?
Water heating is around a third of the average New Zealand household's energy use, and EECA puts a hot water heat pump at 60–75% less electricity than a conventional electric cylinder. EECA's published running-cost comparison is roughly $180 a year against roughly $480 for a standard electric cylinder. Treat those as national modelling rather than a quote for your house — your actual saving depends on how much hot water you use, how old your current cylinder is, and what you pay per unit. We would rather work that out with you than put a number on a website.
What size cylinder do I need?
As a rule of thumb: around 180 litres suits one to two people, 270 litres suits three to four, and 300 litres or more suits larger or heavier-use households. One thing worth knowing — a heat pump reheats a cylinder more slowly than an electric element does. Because of that it is usually worth going a size up from the cylinder you have now, so a run of back-to-back showers doesn't drag the electric element in to catch up.
Do I need building consent?
Usually not. Under the Building Act's Schedule 1 exemptions, replacing an existing storage water heater with a heat pump in the same location does not require building consent, provided the work is carried out or supervised by a registered certifying plumber. A new installation in a new build, or moving the cylinder to a new position, is a different matter. We'll tell you which one you're looking at before any work starts.
My cylinder is on ripple control — what happens to that?
This is the Dunedin-specific question, and it catches people out. Aurora Energy, the lines company here, can switch hot water cylinders off during peak demand — typically for a couple of hours at a time on cold-season mornings and evenings — and households on that arrangement get a lower line charge in return. A hot water heat pump doesn't necessarily drop onto that same control circuit the way a resistance element does. Get it wrong and you can quietly lose the tariff you were on. We work out how your unit should be controlled and scheduled as part of the job, rather than discovering it on your next bill.
Is there a government grant for this?
No. Warmer Kiwi Homes covers insulation and high-wall space heating heat pumps — it does not fund hot water heat pumps. There is currently no national grant or council subsidy in Dunedin for hot water heat pumps specifically. If that changes we'll say so; in the meantime, don't let anyone imply a subsidy exists.
How long do they last, and what does one cost?
EECA puts the typical lifespan at around 15 years and the average cost, including installation, at around $7,000 — against roughly $4,000 to buy and install a conventional electric cylinder. The real figure for your place depends on where the cylinder sits, what the existing pipework and switchboard look like, and which unit suits the position. We'll give you a fixed price after we've seen it, not before.
How does this compare to solar hot water?
They solve the same problem differently. Solar hot water is very effective when the sun is on the collectors and needs a backup element when it isn't — which, in Dunedin, is a real part of the year. A hot water heat pump runs day or night, in cloud, and through winter, and its output doesn't depend on the sky. We install both, so we've got no reason to push you toward one. If you're weighing them up, that's a conversation worth having before you commit to either.
Also worth
a look.
Heat pumps for your rooms
Five brands of space heating heat pump, plus a free Heating Plan before you spend anything.
Solar PV & solar hot water
Pair a hot water heat pump with solar PV and run it on power you generated yourself.
Building a new home?
Decide hot water at the plan stage — it's far cheaper than changing it after the walls close up.
Tell us what
you've got. We'll
tell you if it's worth it.
Or call us on 03 455 3333. We're in the workshop 8am–4:30pm, Monday to Friday.
It helps to know the age of your current cylinder, where it sits, and how many people are in the house — but don't worry if you're not sure.