The right information is essential when choosing a heat pump.
Find the right heat pump for your needs.
A heat pump can cool a room as well as heat it, allowing you to use it as an air conditioner. We analysed the performance data of virtually every heat pump on the market and developed a step-by-step guide to help you choose the right model for your home. We’ve also got all the hottest tips on the most effective ways to use them.
The smaller versions are designed for a single room; the larger, for a whole house. It takes 10 to 30 minutes to bring a room up to temperature, after which the level will be maintained within 1 or 2 degrees.
A heat pump works by extracting heat from the air outside your house and bringing it indoors. It's like a refrigerator in reverse. By trying to cool the world it can extract heat, or vice versa.
Use an old-style bicycle pump for a while and it will get hot. That's because gas (air) is being compressed. Spray an aerosol can and the valve area will become cold. That's because the compressed gas in the aerosol can is expanding.
Heat pumps (like refrigerators) have a system of pipes containing gas (refrigerant) that is continuously expanding in one part of the system and compressing in another. When the gas is being compressed, it gets hot. A heat pump's exterior unit compresses the gas, then pumps it to the interior unit where the gas runs over a series of finned coils, giving off its heat.
The gas is then returned to the outside unit, where it expands and runs through another set of finned coils, which become cold. The cold gas is then recompressed and the cycle continues. For summer cooling, the refrigerant flow is reversed, so the interior unit becomes cool, while the exterior cold.
Heat pumps shift more heat than the electrical energy consumed in compressing the refrigerant and running the fans, making them highly-efficient methods of heating – up to 3 times as much in the right conditions.
This has a major influence on performance. Older models and really large heat pumps larger use R-410A. It still works efficiently but it shouldn’t be your first choice.
Newer models use R32 refrigerant which is more efficient and more environmentally friendly. Make sure you select a model with R32 if there’s one available in your required size.
Is a heat pump the same as a ventilation system?
No. A heat pump uses refrigeration principles to shift relatively large amounts of heat in or out of your home to warm or cool it. A domestic ventilation system shifts drier air from the ceiling space into the living space, and is designed to reduce condensation.
Warm, dry and comfortable
Heat pumps can provide a level of all-round comfort not easily obtained by plug-in electric heaters. They can quickly bring a room up to temperature and then maintain it.
Lower heating costs
If you install a heat pump and keep your home about as warm as you do now, you could save a considerable amount in heating costs. But some of our members with heat pumps tell us they use their units to keep their homes warmer than before, so their heating bills haven't dropped by much.
No gas charge
If you install a gas heater, you'll have to pay a gas connection charge (often around $40 per month) all year round, for a heating appliance you use for less than a whole year.
A reverse-cycle heat pump is the only type of home heating system that can both heat and cool a room.
Do heat pumps dehumidify?
Many modern heat pumps incorporate a washable filter unit that removes dust and particles from the air. This could be an important feature for people with asthma and allergies. The filters need regular cleaning to keep the unit working at maximum efficiency. Some have a deodorising function as well.
A heat pump installation may also add to your home's resale value.
Whirring fans can be very annoying. Fans run in both the interior and exterior units all the time they are switched on. The fan in the inside unit of a heat pump should produce little more than a low hum in low-speed mode, but the compressor plus fan of the outside unit can be quite noisy. Check the manufacturer's specifications. Also, consider the impact on neighbours if the outdoor unit must be mounted near their sleeping areas.
Our 2009 member survey found noise was more likely to be an issue with older heat pumps – 15 percent of those bought before 2004 made enough noise to be "mildly disturbing". This fell to 7 percent for models less than 2 years old.
Not so good in low temperatures
Extracting heat from outdoor air gets more difficult as the temperature drops. Sometimes, especially on frosty nights, exterior heat pump units freeze up and have to stop working for several minutes while they defrost. If you live in a frosty area see "What are your needs" for more about this problem.
Overall, 8% of members in our 2017 appliance reliability survey said their heat pump had not performed adequately on cold, frosty mornings.
Circulating air can cause draughts – which means you need to think about where to place the unit. You don't want one on the wall just above your favourite armchair.
We've created a step-by-step guide to finding the right heat pump for you.
Single-split air-to-air models are the most common type of heat pump in New Zealand. These consist of a single outdoor unit (the compressor) connected to an indoor unit via a system of pipes. They’re designed to heat one room, not your whole home, and you may require multiple units if you have more than one living area.
But there’s many other heat pump technologies out there, including multi-split (where one outdoor unit serves several indoor units), ducted (where a large centralised compressor sends hot air via ducting throughout the home) and air-to-water systems where a heat pump is used in lieu of an electric water cylinder. There are also ground-source heat pumps, which use heat from the earth rather than from the air. These systems remain a niche market, so our round-up only includes single-split air-to-air models.
The Energy Rating Label has a scale of stars to show how energy efficient a model is, compared to other models the same size/capacity. More stars = more energy efficient.
The energy consumption figure is in kWh and can be used to compare with any other heat pump. You can use this figure and the kWh cost from your latest power bill to calculate how much this model will cost to run. The average cost of power for a kWh in New Zealand is 25¢. Lower kWh = cheaper to run.
The product’s annual energy consumption in kilowatt-hours (kWh) is based on standards testing. Check the key assumptions used in this testing to make sure they match how you will use the product. Annual energy consumption for heat pumps assumes full output capacity can be achieved with an outdoor temperature of 7°C when heating and of 35°C when cooling. You should only compare star ratings of heat pumps with the same or similar capacities.
For information on energy ratings and how to use them, see our Energy Rating Labels explained article.
Over the past few years, New Zealanders have taken to heat pumps like ducks to water, and they’re now our third most common heating choice after woodburners and plug-in electric heaters. But a report last year by the Building Research Association of New Zealand (BRANZ) found it hasn’t all been plain sailing.
The report is based on a study of 160 New Zealand households with heat pumps. While most said they’d recommend a heat pump to friends or family, almost a fifth weren’t overly satisfied with their heating performance. To make matters worse, 31 percent didn’t understand how to properly use their heat pump, often as a result of not being provided the right information by their installer. Other commonly reported issues included:
The study also uncovered shocking examples of shoddy installation. These weren’t isolated cases – 33 percent of units were installed with less than the recommended clearance from the ground, which can affect performance and reduce lifespan.
Safety issues were also too common. In 19 percent of installations, the heat pump’s water drainage hose discharged directly on to paths, which makes them slippery, encourages moss and poses a hazard if the path ices over.
Returning to a home that’s set to the perfect temperature is pure bliss. Heat pumps let you do this, but many have remote controls that are over-complicated, putting the use of timers into the too-hard basket for many of us. A solution is a heat pump with WiFi, which shifts control to an app on your smartphone or tablet.
We recommend trying a few brands, as each has their own flavour of WiFi control. Some controllers are built into the heat pump, while others are plug-in units. You should ask for a demonstration and have a go using it.
COP (Co-efficient of Performance)
The COP is a technical calculation of heating efficiency which is used in the formula for calculating star ratings. For heating, a good unit has a COP of 3 or more. The heating COP can be reduced by cold temperatures because de-icing takes extra energy.
Energy efficiency ratio (EER)
This is the calculated cooling efficiency, and is also used to calculate the star rating. The higher the rating, or the more stars, the better. An EER of 3 or more is good.
All heat-pump/air-conditioner units imported or manufactured after 16 June 2006 must meet a new Minimum Energy Performance Standard or MEPS. But these minimums are set quite low, particularly for larger units.
MEPS has little relevance to your buying decision – it's there to make sure manufacturers don't sell unacceptably inefficient heat pumps to unsuspecting consumers.
We answer your frequently asked questions about heat pump performance and heat pump corrosion.
Some maintenance requires professional help – but much of it you can do yourself. That’s provided you don’t mind standing on steps to reach inside units mounted high on the wall. If steps are a problem, get professional help.
These collect the dust and dirt that’s removed from the air passing through the indoor unit. The most regular maintenance job is filter cleaning. If the unit’s been operating for a few months or more the filter’s likely to be quite dirty.
Removing the filter(s) is relatively simple – see your instruction manual. In most models you lift the front cover and slide out the filter.
Take the filter to the bath or shower (or outside) and spray it with a neutral “spray & wipe” type of cleaner, then rinse it thoroughly. Repeat if necessary. Don’t use solvents or other harsh cleaners.
You can get dedicated filter-cleaning sprays from refrigeration wholesalers. They’ll make the air delivered by the heat pump smell nice – but they won’t clean the dirt any better.
Other indoor cleaning
While you’re dealing with the indoor unit, inspect the cylindrical fan vanes – and also the heating/cooling fins – for dirt build-up. Use your vacuum cleaner’s upholstery brush to gently vacuum dirt away from the vanes and the fins. Finally give the outer casing a wipe with a soft cloth dampened with a squirt of neutral spray & wipe cleaner.
How often? If you have carpet and the heat pump runs for many hours a day all year round, the filters could need cleaning four times per year. Cleaning will be less frequent if you run the heat pump less or have hard floors. For a heat pump that runs for a few hours a day mainly for heating, then once a year in the autumn should be enough. If the heat pump is used regularly for cooling as well, then go for an autumn and spring clean.
The first job with the outdoor unit is to make sure air can get to and through the unit without obstruction. That means clearing away any vegetation that could reduce airflow. Next, make sure the air grilles each side of the unit are clear of debris such as leaves and twigs.
Inspect the fan blades, fins and the outer casing for signs of corrosion. Rust never sleeps, so deal with corrosion – or get it dealt with – as soon as possible. This will lengthen the life of the unit.
How often? A heat pump used mainly for heating only needs a maintenance check once a year in the autumn. If you use the heat pump regularly for cooling, then look at doing another check in spring.
Even if you do the basic cleaning yourself, getting a professional to check the heat pump every couple of years is worthwhile. Professionals can measure the delivered air temperature and check the unit is operating properly. Probably the best professional to use is the person who installed the unit.
Tip: Beware of cold-calling, high-pressure outfits that try to bulldoze their way on to your property. See our October 2014 news article for more on this.
We've assessed 256 heat pumps.
Find the right one for you.