Heat pumps

To get the most out of a heat pump, it's important to choose an efficient model and use it properly - here's how.

Types of heat pump

  • Single-split systems are the most common heat pumps in New Zealand - they are air-to-air, with one indoor unit connected to an outdoor unit. These systems are designed to heat just the room that they are installed in, not the whole house. While leaving internal doors open may allow some of the heated air to travel into other rooms, in most houses this does not work very well, particularly if there is a hallway in between, if there are high ceilings or if the house needs a lot of heating.
  • Multi-split heat pumps are designed to heat multiple rooms - and consist of one outdoor unit serving multiple indoor units installed in different rooms of the house.
  • Ducted heat pumps provide central heating - by blowing heated air through ducts into multiple rooms of a house. While some can only be controlled centrally, others allow you to choose which rooms or groups of rooms you want to be heated at any given time (zoning). For example, you may only want to have your bedrooms heated overnight.

Choosing an efficient model

Heat pumps are the most efficient way of using electricity to heat your home, but some are much more efficient than others. Look for the Energy Rating Label – the more stars, the more energy efficient.

What’s more, some heat pumps struggle to perform at cold outside temperatures just above freezing point. If you live in a cooler climate, ask your supplier if the heat pump you're looking at performs well and efficiently at cooler temperatures, and get it sized for the room you want to heat.

Heat pump checklist

  • Insulate first - starting with your ceiling and floor. You'll be able to buy a smaller heat pump and your home will be cheaper to heat and cool effectively.
  • Choose a quality brand - from a reputable supplier that offers at least a 5-year warranty on parts and labour.
  • Make sure it's correctly sized - for the room you want to heat. If it's too small, it may cost you more to run and will struggle to provide enough heat when you most need it. Your supplier will be able to discuss this with you.
  • Make sure it is well-installed - ask your installer if they comply with the EECA Good practice guide to heat pump installation. Correct location and installation of both outdoor and indoor units is essential for optimum performance and for avoiding draughts and noise nuisance.
  • Make sure it’s right for your climate - as the temperature drops, so does the performance of many heat pumps. A good quality unit - sized and installed correctly - should perform effectively down to minus 15°C. If you need your heat pump to perform at these temperatures, ask your heat pump supplier for advice.
  • Make sure it’s right for your environment - in geothermal areas or coastal areas, heat pumps need to have suitable protection against corrosion. Ask your supplier about environmental considerations in your area.

Using the Energy Rating Label

All heat pumps display the Energy Rating Label to help you compare the efficiency of similar sized models. The more stars, the more energy efficient a unit is - red stars are for heating efficiency and blue stars are for cooling.

Understanding the numbers

A heat pump label has two numbers that can tell you more about the heat pump's performance:

  • capacity output - the amount of heating or cooling (kW) you will get out of the heat pump (at its rated capacity, at 7˚C)
  • power input - the amount of power the heat pump uses (kW) to produce the cool or hot air.

You can also use the numbers to calculate heating efficiency of a heat pump - the higher the ratio, the more efficient it is.

  • Coefficient of Performance (COP) - the ratio between the heating power input and capacity output, for example 4.75 divided by 1.64 = 2.90
  • Energy Efficiency Ratio (EER) - the ratio between the cooling input and output, for example 4.45 divided by 1.61 = 2.76.

Using heat pumps wisely

  • Only heat when you need it - don't leave your heat pump on all day if you're not there.  Use the timer to turn on the heat pump shortly before you get home and turn it off when you don’t need it.
  • Only heat the space you're actually using - shut doors and curtains to keep the heat in.
  • Set the thermostat to a healthy temperature - aim for 18ºC to 20ºC. High thermostat settings cause high electricity use. Inadequate heating can lead to mould growth and dampness.
  • Avoid using the 'Auto' mode - use the 'Heating' mode. In 'Auto' mode, the heat pump tries to maintain the set temperature by constantly changing between heating and cooling, as the room temperature fluctuates. This can waste a lot of energy.
  • Clean the filter regularly - inside and outside, as per the manufacturer's instructions.
  • Avoid using it as an air conditioner when you can - try opening windows and doors on either side of the house to create a through-breeze. Close curtains on hot, sunny days to keep your home cool and shady.

 

Video - How to clean your heat pump.