0:04 — Why I’m replacing my gas hot water

Carolyn: Kia ora, my name’s Carolyn Cox from Goes Electric. Today I’m going to have a hot water heat pump installed. This has been something that I’ve been looking forward to and planning for a long time. This is my old gas hot water unit that I’ve had for about 13 years. Gas used to be the cheapest form of hot water heating in New Zealand. Now it is the most expensive. It’s costing me $700 a year just in the daily gas charges alone. It also comes with quite a big carbon footprint. Putting this hot water heat pump in is going to be much more efficient and much cheaper, so I’m really excited about that. We put in the concrete pad about a week ago to give the concrete time to cure, and very soon the new unit is going to be going up.

0:45 — Why Rinnai split the cylinder from the heat pump head

Craig Davidson, Operations Manager, Rinnai: We spoke to the installers before we were developing the product. Not only were they heavy, they were very tall and unwieldy to move around. So what we did was split them into the hot water cylinder, which is essentially just a large hot water cylinder, and then all the working parts sit on the top. So the guys have a normal installation of the cylinder, and then it’s a two-man lift for the 30 kilogram head on the top of it. So it’s a whole lot safer and a whole lot easier for their logistics getting it onto the site.

1:14 — Disconnecting gas: the cheap way and the costly way

Carolyn: You can tell I’ve been trying to hide this. This down here is my gas meter. There’s a bit of confusion in New Zealand around what you can and can’t do with disconnecting your gas. It’s a bit grubby, but there are two ways of going about it, and one’s much more expensive than the other. You can basically just disconnect at your meter, and then you’ll get a final gas reading and there’s no further need to pay daily gas charges. Some gas companies will charge you to do the disconnection and the final reading, others won’t, so check that out. Don’t be confused though: some will quote you for disestablishing the gas connection. That’s basically a charge to pull that out and take the whole connection out to where your street connection is. And I’ve seen people being quoted thousands and thousands of dollars to do that. You don’t actually need to do that. You can just simply disconnect it here and it’s much cheaper. So I really recommend doing that. View the Goes Electric Getting off Gas Guide

2:10 — A noise baseline before the new unit goes in

Carolyn: A lot of people are concerned about the noise from hot water heat pumps, and I thought it would be good to do a bit of a comparison so you could hear what this is like before we install the new unit. I’ll be quiet now so that you can see the decibel limit, roughly.

2:32 — Installation day and choosing a tank size

Callum Massie, General Manager, Laser Plumbing Grey Lynn: So it’s not too dissimilar to swapping out a standard electric cylinder. The only real difference is the air conditioning unit on the top, which obviously helps to add efficiency to the unit and helps it run a lot more sustainably for homeowners. We typically find that, depending on what adaptation is needed to the pipework, it could be a full day required to install the unit. In terms of working out the right tank size, Rinnai has a really easy-to-follow guide on their website that highlights all the specifications for each unit. If you do choose something that’s going to be too small for the household, it just means you might not get enough hot water for those long showers. From a plumbing perspective there are a few differences in the size and location of where the units can be installed, but from an actual pipework perspective it’s not too different. The Rinnai Hydraheat comes in two sizes: 275L and 340L Search hot water heat pumps by cylinder size Goes Electric hot water heat pump size calculator

3:16 — Condensate drainage, tempering valve and tapware

Callum Massie, General Manager, Laser Plumbing Grey Lynn: What we typically do is set it up to drain into the nearest gully. And it is really important to get that right. You don’t necessarily want that condensate draining right next to the cylinder over time. If that area is constantly wet and water’s just dripping through, it could actually impact the integrity of the soil or the surrounding area. The tempering valve ensures that we’re keeping the temperature of the hot water at a compliant and safe temperature. If that’s not included, there’s a risk that the customer actually burns themselves at the outlet. There shouldn’t really be a restriction if the house is on low pressure. Probably the biggest thing we need to take into consideration is that the tapware within the house is fit for purpose and is going to operate properly with a new mains pressure system. Obviously if anything is substandard, we’ll upgrade it to current code.

4:17 — Plumbing, electrical, dedicated circuits and timers

Callum Massie, General Manager, Laser Plumbing Grey Lynn: Obviously when installing a hot water heat pump, there’s both a plumbing and an electrical component, and sometimes a gas component as well if you are moving away from an existing gas unit. We can work with other electricians and help minimise the communication and back and forth for homeowners. But equally, we always advise that if you’ve got an electrician that you work with and know and trust, you can link them in with us or coordinate them on your own behalf. Liston Tupou, Electrician, Laser Electrical Rosebank: For the electrical side, we run a dedicated circuit from the switchboard all the way out to the outdoor hot water cylinder. So if anything that was tapped off it were to trip, it wouldn’t trip the hot water unit. Say if you had it off a power point, it would also trip the power point as well as the hot water. It’s pretty universal. It just depends on space in your switchboard, if it makes it a bit hard if there’s no space, and probably the state of it. Most of these units are pretty universal; you can get them in anywhere. The paperwork that we provide is mainly a COC and an ESC, which covers the safety of the install and also the compliance for the homeowner. Kaleb Hoole, Project Manager, Laser Electrical Rosebank: This particular cylinder can use the benefits of off-peak rates. This one has built-in timers, so you can programme it to come on when the power is cheaper, and you can set it up to run during the sun hours for solar. Callum Massie, General Manager, Laser Plumbing Grey Lynn: It’s definitely the type of work that needs to be done by a registered and licensed tradesman.

5:54 — Red flags, seismic straps and common mistakes

Callum Massie, General Manager, Laser Plumbing Grey Lynn: Plastic piping is a big red flag. Another is having outlets or drains that just drain straight next to the side of the cylinder. Another sign could be if a unit’s been installed on a grass area and there’s not a suitable pad or concrete path to take the weight of the unit. Once filled with water they can be incredibly heavy. In the case of an earthquake, they need to be seismically restrained to ensure they stay upright. If any unit is under 200 litres, it needs two straps. If any unit is over 200 litres, it needs three straps, and they need to be stainless steel as well. Robert Beardmore, Training Manager, Rinnai: The most common mistakes are maybe the insulation not being done properly, or the unit not having the right clearances, so the airflow is not getting to the head unit, which will mean it won’t be running as efficiently. Maybe the base is not quite right, or we’ve got a slope to it. But I think that mainly, for the homeowner anyway, further down the line it will be the efficiency of the unit.

7:05 — Certificates, manuals and warranty paperwork

Robert Beardmore, Training Manager, Rinnai: You’ll be getting two lots of paperwork: one from the plumber or the installer, who’ll be certifying his work, so the plumbing work. And then you get a certificate of compliance for the electrical work as well. So those are the two main ones. They should also be leaving you with the installation and operator manual. That’s important. And obviously the warranty side of things, so that’s really important. If it’s just a normal cylinder like yours here and there’s no major work going on, then you wouldn’t need a building consent for that [verify wording: transcript unclear]. But if it’s something out of the ordinary, or you’re building something purpose-built around it, then yes, you may need that.

7:50 — Getting and comparing installation quotes

Callum Massie, General Manager, Laser Plumbing Grey Lynn: When looking for quotes for installing and upgrading to a hot water heat pump, probably the most important thing, same as with anything, is to work with trustworthy tradespeople. So either ask friends and family who they’ve had a good experience with, look at online reviews, look at people’s websites. The biggest thing is making sure the person you’re using has a track record, and a level of trust and professionalism. It often pays to get two to three different quotations, making sure the messaging you’re giving to the tradespeople is the same. A big thing to bear in mind: if someone has a drastically lower price than somebody else, they may be cutting corners to make that happen, and there could be other costs that come up at the back end of the install when you realise a couple of things haven’t been included.

8:43 — Switch-on time!

Carolyn Cox: So it’s now just about one o’clock. We started about quarter past eight this morning and we’re just about to turn this on. The exciting thing is that within about half an hour there should be enough hot water in here to have our first hot shower. So now I am going to turn the switch.

9:12 — How a hot water heat pump works

Craig Davidson, Operations Manager, Rinnai: So this is your first hot water heat pump. Now that it’s installed, what you need to know is: where’s my soap? Because I’m going to go and have a shower. Really, there’s not a lot you need to know. It’s a piece of magic in the background that will just deliver the hot water to your house. There are things you can do with it, there are settings you can play with, or you can be like most people and just treat it as a piece of magic. A hot water heat pump combines two bits of great science: physics and thermodynamics. The first part of it is if you take a gas and you squeeze that gas, it gets hot. And if you’ve got a compressed gas and you release that pressure, it gets cold. The thermodynamics part is if you’ve got a hot thing and a cold thing and you put them next to each other, energy flows from the hot thing to the cold thing. So if we take that squeezed hot gas and we put it up against cold water, the heat moves from the gas into the water. And then you take that gas, which has lost a lot of its heat, and you release the pressure, it gets really cold, and it sucks heat out of the air. So what you’ve effectively done is taken heat out of the air and used the gas to push that heat into the water.

10:22 — Built to be repaired

Craig Davidson, Operations Manager, Rinnai: A lot of the heat pump units we’re seeing come into the country are very much breakdown-throwaway, and that’s not our ethos. So inside here, we’ve designed it so if a pump fails, you can change the pump. If the sensors fail, you can change the sensors. Everything that’s practically part of the plumbing system is removable and replaceable. And if the worst were to happen and something goes wrong with this main heating unit, we can remove it and take it back to a workshop to work on it. Meanwhile, this turns back into a standard hot water cylinder and you’ve still got hot water. If the heat pump unit itself fails, the element will take over in the hot water cylinder. The element’s normally not active unless the heat pump shuts itself down. You can remove the unit, take it away for repair, and bring it back again. Whenever you’ve got a problem with any plumbing installation, the first thing is to give your installer a call. But if you don’t know who your installer is, call Rinnai. We’ve got a help desk full of people who can talk you through those processes.

11:27 — Noise and where to put it

Craig Davidson, Operations Manager, Rinnai: Right now it’s running and the noise level is very, very low. You’ll notice that the fan system inside it, when we were putting it together, is actually directed upwards, so most of the noise coming out of it is actually going up into the sky. Where you should put it, though: be polite to your neighbours. You don’t want to put it too close to your fence. Don’t put it underneath the bedroom window. But if you do find that night-time operation is causing you an issue, you can set the timers so that it only runs during the day. Goes Electric Installation Guide

12:00 — Standard, eco and boost modes

Craig Davidson, Operations Manager, Rinnai: You’ve got 340 litres of water here. That’s an awful lot. That’s a lot of showers. So my advice would be to stick with that for a while. If you find you always have plenty of hot water, then you can play with the efficiency settings. You could, for example, move it to eco mode. Eco mode stores the water at a slightly lower temperature, which means slightly less loss of heat and a slightly more efficient heat pump. But start with the standard mode and see how you go. You can also put it into a boost mode if you want the heat pump and element operating. The element normally stays off, but in boost mode you’re putting the maximum amount of energy into it.

12:36 — Efficiency and New Zealand conditions

Craig Davidson, Operations Manager, Rinnai: Compared to a standard electric cylinder, where if you take one kilowatt of electricity and push it into the element you get one kilowatt of heat, with this unit, on average, you’ll get about four and a half kilowatts of energy for every kilowatt of electricity you put in. So that’s getting close to 80% less energy used to heat the same amount of water. That varies according to climate conditions and whether you’re in eco mode or standard mode, but that general percentage of about 75 to 80% is generally about where you are. If it’s a really cold night, then the efficiency drops a little bit and you’re probably moving into three-to-one territory. If it’s a really warm day in the far north of the country, that might be six-to-one territory. But that’s the range you’re working in. One of the reasons we’ve specifically engineered for New Zealand is that in most countries you’ve got a wet summer and a dry winter. In New Zealand, we generally have wet winters and dry summers. And in a wet winter, high humidity and condensation with cold temperatures can be a bit of an issue. The only issue you’ll find is that there’ll be some frost build-up on this. The system has a defrost cycle, but to run that defrost cycle we lose a bit of efficiency. So it’ll still function, and it’ll still be more efficient than a standard hot water cylinder, just not as good as if it was the middle of summer. What is COP? Understanding Heat Pump Efficiency

14:01 — Durability testing and warranty

Craig Davidson, Operations Manager, Rinnai: As part of the development process, we built several prototypes of these, and we put one of them into a hard endurance testing environment where we were heating the water, running all of that, heating the water, running all of that, so it was doing multiple full cylinder cycles a day. We’ve simulated over 10 years of operation, and we’ve still got the same pump, the same compressor, the same everything, and it’s still functioning like the day we installed it. The warranty on this is five years, and seven years for the tank, but we have an expectation it’ll last a lot longer than that.

14:36 — R290: a natural propane refrigerant

Craig Davidson, Operations Manager, Rinnai: The refrigerant we use in this heat pump is a hydrocarbon called propane, which in the refrigeration world is called R290. It’s considered a natural refrigerant because it’s naturally generated; it’s not one of the chemically created refrigerants. It’s got no fluorines in it, so we haven’t got ozone layer issues, and it’s got a very low global warming potential: a GWP of three. That compares to some of the other common refrigerants like R32, which is in the 600 to 700 range, or the old R410A, which is over 2000. So compared to the other refrigerants you might see in a system, it has a much lower greenhouse potential.

15:20 — Power cuts and single-pass heating

Craig Davidson, Operations Manager, Rinnai: In the event of a power cut, this will stop working, but you’ve still got 340 litres of stored hot water, and there’s a very thick layer of insulation around this to keep that heat inside. It won’t last forever, but you’ll have several days of warm showers. The concept of this one is what’s called top-down water heating, or single pass as it’s sometimes referred to. A single-pass heat pump means the cold water leaves the bottom of the hot water cylinder, runs through the heat pump, and goes back into the top of the cylinder at the set temperature. So it doesn’t have to go through multiple passes, which means that while it’s running now, it’s filling the cylinder with hot water from the top down. The bottom of this cylinder is still dead cold, but the top is now usable, showerable water. If we compare that to the recirculating heat pumps, they’re passing the water through the heat exchanger of the heat pump multiple times, adding a few degrees of temperature each time. So you start with a cold cylinder, then a slightly tepid cylinder, then a bit warm, then warm, and eventually you’ve got a hot water cylinder. About four hours later, you can have a shower. So it’s a really important difference. It also makes a difference from the thermodynamics point of view: because we’re taking really cold water and putting it up against the heat exchanger, we get maximum heat transfer, rather than taking warm water where the heat transfer is not as efficient. That means this unit is running at maximum efficiency from start to finish, rather than dropping off a bit as the cylinder gets full.

17:04 — First non-gas heated hot water in 17 years

Carolyn Cox: We’ve had a hot water heat pump running here for 40 minutes now. I’m about to turn on the tap and see whether we’ve got some hot water. Yep, we’ve got hot water. So that’s exciting. This is the first time I’ve had hot water in my house in 17… it’s getting really hot now. This is the first time in 17 years that I’ve actually had hot water not produced by gas. So that’s really exciting. It comes with a much lower carbon footprint. I hope you’ve learnt a lot watching the video today. If you’re interested in finding out more about hot water heat pumps or other home electrification options, please follow us at goeselectric.nz. Thank you.

Rinnai Hydraheat Hot Water Heat Pump Installation

My gas hot water unit was about 13 years old and costing me around $700 a year in daily gas charges alone. This video was filmed on the day I disconnected from gas and swapped it for a Rinnai HydraHeat 340L hot water heat pump at my Tāmaki Makaurau Auckland home.

By Carolyn Cox · Sustainability Expert, 25+ years · Updated 30 October 2026

In a day packed with excitement - for me anyway! We pulled out my old gas califont, disconnected the gas and installed my brand new hot water heat pump!

Along the way, I interviewed Rinnai’s expert product team to uncover why the Hydraheat is built the way it is: a separate heat pump head that can be repaired or removed, top-down water heating, and a propane refrigerant. Covering how it works and why it is so much more efficient than gas or a traditional electric hot water cylinder. And to also uncover how I could operate it in the most efficient way possible.

“On average, you’ll get about four and a half kilowatts of energy for every kilowatt of electricity you put in.” Craig Davidson, Rinnai

The installation team from Laser Plumbing Grey Lynn, Laser Electrical Rosebank and Rinnai also walk us through what to check on the day, from drainage and tempering valves to dedicated circuits, seismic straps, all the paperwork you need and how to look for a good quote.

Watch "Hot Water Heat Pump Installation NZ | Rinnai Hydraheat" on YouTube

In this video, you'll learn

Carolyn Cox wearing a read top putting on glasses to view computer on table.

Wet concrete pad with grass in foreground and white weatherboard wall behind.

Follow my gas-to-heat-pump swap from start to finish in my Tāmaki Makaurau Auckland home. We cover:

What happens when you replace gas hot water with a heat pump
How the installation works, including the plumbing and electrical requirements
What a hot water heat pump sounds like, and where to put it
How quickly this new system starts producing hot water
How heat pumps work and why they use less electricity
How to choose the right tank size
What certificates, warranties and paperwork to ask for
Common installation mistakes, red flags and what to consider when comparing quotes
How timers and operating modes can help you use electricity more efficiently

Transcript

The Rinnai Hydraheat

Image showing Rinnai Hydraheat hot water heat pump located outside a modern timber home on wooden deck with garden surrounds and outdoor dining set.

Rinnai Hydraheat Split Model shown outside a masonary home on concrete step with garden lawn surrounding.

Key takeaways

Disconnect at the meter. Ask your gas company for a disconnection and final reading, not a “disestablishment or decommissioning” of the whole connection. Find out more Goes Electric Guide to Getting Off Gas.
Use registered, licensed tradespeople, and expect a dedicated circuit. The electrical work runs on its own circuit from the switchboard. Ask for the installer’s certification of the plumbing work, the Electrical Certificate of Compliance (ESC), plus the installation and operator manual and the warranty.
Avoid future problems. Look for good condensate drainage, a tempering valve, check old tapware, provide a solid pad, ensure airflow clearances, good insulation and stainless steel seismic straps. Plastic piping is a red flag.
Compare two to three like-for-like quotes. Give every tradesperson the same brief. A drastically lower price may mean something has been left out and shows up later as an extra cost.
Expect roughly 4.5 units of heat for every unit of electricity. Rinnai says that is about 75–80% less energy than a standard cylinder, dropping toward 3:1 on cold nights and reaching about 6:1 on warm days in the far north. These are manufacturer figures.
Use the timers and modes. Programme it for off-peak or solar hours, start in standard mode and try eco once you know you have plenty of hot water, and set a daytime-only timer if night-time noise is an issue. Keep it away from fences and bedroom windows.

Experts in this video

Hot water heat pump installation interview crew, eight people dressed in front of gate and beside a hot water heat pump undergoing installation — The installation crew L-R: Liston Tupou, Robert Beardmore, Jason Watson, Craig Davidson, Matthew Matipo, Carolyn Cox, Josh Tamaseu Russell, and Xander Lendrum. · Goes Electric

Craig Davidson, Operations Manager, Rinnai

Craig has lived and breathed product design, manufacture and operations at Rinnai for over twenty years. Craig was integral to the design, manufacture and testing of the Rinnai Hydraheat specifically for New Zealand conditions and knows this product inside out. Traditionally known for their gas hot water heating Rinnai have two core hot water heat pump products available in New Zealand and see these as part of the market transformation in water heating.

Callum Massie, General Manager, Laser Plumbing Grey Lynn

Callum owns and manages the Laser Group Business of the Year 2025 and 2026. Callum’s team services the Greater Auckland area. Offering plumbing, drainage, gasfitting, roofing and backflow prevention for homeowners, property and facility managers across Tāmaki Makaurau. They are specialists in hot water heat pump installation.

Robert Beardmore, Training Manager, Rinnai

A specialist in plumbing installation, maintenance, repairs and technical support, Rob now leads training for plumbers and electricians around the motu on installation of Rinnai’s hot water heat pump systems. Rinnai requires that all products are installed by certified professionals who have completed this training.

Liston Tupou, Electrician, Laser Electrical Rosebank

Liston is a Licensed Electrician with the Laser Electrical Rosebank team working across Auckland to deliver electrical services including many hot water heat pumps.

Kaleb Hoole, Project Manager, Laser Electrical Rosebank

Kaleb manages projects for the Laser Electrical Rosebank team, one of Auckland’s largest and most established electrical contracting companies. Solar, EV chargers, heat pumps, air conditioning and hot water heat pumps are all part of the home electrification services offered.

Resources

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Transcript

0:04Why I’m replacing my gas hot water

0:45Why Rinnai split the cylinder from the heat pump head

1:14Disconnecting gas: the cheap way and the costly way

2:10A noise baseline before the new unit goes in

2:32Installation day and choosing a tank size

3:16Condensate drainage, tempering valve and tapware

4:17Plumbing, electrical, dedicated circuits and timers

5:54Red flags, seismic straps and common mistakes

7:05Certificates, manuals and warranty paperwork

7:50Getting and comparing installation quotes

8:43Switch-on time!

9:12How a hot water heat pump works

10:22Built to be repaired

11:27Noise and where to put it

12:00Standard, eco and boost modes

12:36Efficiency and New Zealand conditions

14:01Durability testing and warranty

14:36R290: a natural propane refrigerant

15:20Power cuts and single-pass heating

17:04First non-gas heated hot water in 17 years