Over the past few months we’ve had a steady stream of calls from homeowners around Warkworth, Matakana and the Kowhai Coast asking the same question: can we get rid of the gas bottles and switch to a heat pump hot water cylinder?
The short answer is yes. For most homes with LPG hot water it’s one of the more straightforward upgrades we do, and with bottle prices where they are, the savings add up quickly. If you’re weighing up whether to replace gas hot water with a heat pump, here’s what we tell our own customers.
Why gas bottle hot water is costing more
Most rural and semi-rural homes in our area run their gas hot water off a pair of 45 kg LPG bottles. A few years ago a delivered 45 kg bottle typically cost around $100 to $120. Today Auckland suppliers are charging roughly $150 to $190 a refill, and that’s before bottle rental, which now runs at about $60 to $107 a year per bottle (That Power Guy price comparison). Most homes have two.
Being around 45 minutes north of Auckland, many of our customers tell us they’re paying at the top end of that range, and they’re getting through bottles faster than they’d like, especially over winter when the incoming water is colder.
Meanwhile, hot water heat pumps keep getting more efficient. The model we install most often is rated to keep working right down to minus 6°C.
How does a heat pump hot water cylinder work?
A hot water heat pump works a bit like a fridge in reverse. Instead of burning gas or running a big element, it uses a small compressor to pull warmth out of the outside air and move it into the water in the tank.
That’s why they’re so efficient. According to EECA, hot water heat pumps run at efficiencies of between 276% and 415%, compared with around 83% for a gas continuous-flow (instantaneous) water heater and 88% for a gas storage water heater. In plain terms, every unit of electricity a heat pump uses puts roughly three to four units of heat into your water.
Gas vs heat pump hot water: what it costs to run
Here’s a simple way to compare them. A 45 kg bottle holds about 620 kWh of energy. A gas continuous-flow heater at 83% efficiency turns that into roughly 515 kWh of heat in your hot water.
To put the same 515 kWh of heat into your water, a heat pump running at a conservative 300% efficiency (allowing for colder winter days) needs about 170 kWh of electricity. At the Auckland average power price of about 40 cents per kWh (MBIE Quarterly Survey of Domestic Electricity Prices, February 2026), that’s roughly $70 of power, compared with $150 to $190 for the bottle of gas.
Example: a household using one 45 kg bottle every two months for hot water
| Gas bottles | Heat pump | |
|---|---|---|
| Energy per year | 6 bottles at about $180 = $1,080 | About $420 of power |
| Bottle rental | 2 bottles at about $80 = $160 | $0 |
| Total per year | About $1,240 | About $420 |
That’s a saving of roughly $800 a year in this example. Your own figures will depend on how much hot water you use, your power plan and what you pay for gas. EECA’s home energy savings calculator is a good way to check your numbers, or we’re happy to run through them with you.
Why we like the Rheem AmbiPower 280e
There are several good hot water heat pumps on the market, but the one we keep coming back to for gas conversions is the Rheem AmbiPower 280e. It’s an all-in-one outdoor unit, so there’s nothing to find room for inside the house.
- 280 litres of storage, which Rheem rates for households of up to six people in moderate and cold climates.
- Very efficient. Rheem quotes a COP of 5.2 at 19°C and says it can cut water heating energy use by over 70% compared with a standard electric cylinder. Efficiency drops on cold days, which is why we used a more conservative figure in the example above.
- Built for winter. It keeps working from minus 6°C up to 43°C, has frost protection, and has a 2.4 kW backup element for cold snaps or times of heavy use.
- Mains pressure. It works with water supplies from 200 to 800 kPa, which covers most town supply and pumped tank water systems.
- Made to live outdoors. A vitreous enamel lined tank, and a painted steel case with an aluminium top cover.
- Lower-impact refrigerant. It uses R290, a low global warming potential refrigerant.
- Solid warranty. 7 years on the cylinder (3 years labour), 3 years on the sealed heat pump system including labour, and 1 year on parts, for domestic installations.
What’s involved in switching from gas to a heat pump
- Site visit and quote. We look at where the unit can go outside, your water supply and pressure (town supply or tank and pump), your existing pipework and how much hot water your household uses. The unit needs a firm, level spot with good airflow. Like any heat pump it makes a low hum while running, so we’ll keep it away from bedroom windows.
- Making the gas safe. Our own gasfitter disconnects your old gas water heater and caps off the gas pipe. It’s usually quick and straightforward, and if a job needs it we’ll bring in a certifying gasfitter. If hot water was the only thing running off your bottles, you can ask your gas supplier to collect them and stop the rental. If you still cook with gas, keep the bottles for the hob and they’ll last a lot longer.
- Base and installation. The AmbiPower 280e weighs about 135 kg empty and over 400 kg once it’s full, so it sits on a solid base such as a concrete pad and is restrained against earthquakes. We connect it to your hot and cold pipework and fit the required safety valves.
- Power supply. A registered electrician connects the heat pump to its own circuit.
- Commissioning. We set the unit up, check everything is running as it should, and talk you through the best way to run it on your power plan, including cheaper off-peak rates or daytime solar if you have it.
Your hot water is stored at 60°C or hotter to control Legionella bacteria, and a tempering valve keeps water to your showers and basins at a safe 55°C or less, in line with the Building Code.
Do I need a building consent?
Usually not. Exemption 38 in Schedule 1 of the Building Act 2004 allows any water heater to be replaced, including moving it to a new position, without a building consent, as long as the new unit has a controlled heat source and the work is done by an authorised plumber. MBIE’s guidance on exemption 38 even gives the example of replacing an indoor water heater with an outdoor heat pump unit.
Our certifying plumbers carry out the plumbing and provide the paperwork, our gasfitter makes the gas safe, and a registered electrician certifies the electrical connection. If your job involves anything outside the exemption, we’ll tell you upfront.
Is a heat pump right for your home?
For most homes on gas bottles it’s a great fit, but it’s worth knowing the trade-offs:
- Upfront cost. EECA puts the typical cost of a hot water heat pump at around $7,000 installed, compared with about $4,000 for a gas or standard electric system (EECA). The lower running costs are what pay it back over time. Every home is different, so give us a call for a free quote.
- Outdoor space. The AmbiPower 280e is about 1.83 m tall and around 700 mm across, so it needs a suitable spot outside.
- Stored hot water. Unlike a continuous-flow gas unit, a cylinder holds a set amount of hot water. For most families 280 litres, backed by the booster element, is plenty. For bigger households or several bathrooms, we’ll size the system to suit.
Not sure what you’ve got now or what would suit? Have a look at our hot water cylinder services, or give us a call.
Frequently asked questions
How much does it cost to replace gas hot water with a heat pump?
EECA’s typical figure for a hot water heat pump is around $7,000 installed, but every home is different, depending on where the unit goes, your pipework and the electrical work needed. Call us on 0800 786 777 for a free quote for your home.
Will a heat pump hot water cylinder work in winter?
Yes. The Rheem AmbiPower 280e keeps working down to minus 6°C, and its backup element tops up the heat on the coldest mornings. It’s less efficient on a frosty morning than on a summer afternoon, but still much cheaper to run than bottled gas.
Can I get rid of my gas bottles?
If hot water is the only thing using gas, yes. Once we’ve capped off the gas, contact your supplier to collect the bottles and end the rental. If you cook with gas, you can keep the bottles for the hob.
Which areas do you cover?
We work right across Rodney and North Auckland, from Mangawhai to Albany, including Warkworth, Matakana, Snells Beach, Omaha and the Kowhai Coast.
Ready to ditch the gas bottles?
Talk to our certifying plumbers about switching to a heat pump hot water cylinder. Call 0800 786 777 or book a free quote online.