If you're thinking about buying a heat pump, you need to consider the climate you live in and the features you require.

Climate

In areas with hot humid summers, good cooling performance may be important. If you live in a colder area, you'll want a model that has good heating performance. Look for a model that claims to be able to operate at temperatures below the worst you'd expect.

When the outside unit of a heat pump detects ice, it will automatically de-ice and stop producing heat. This is most likely to occur as the air temperature approaches freezing (at below-zero temperatures all the water in the air will have frozen and formed frost or snow, so the unit should no longer ice up). This can happen to all heat pumps but some do a better job of cold-weather performance than others.

H2 output capacity

This shows the heat output capacity of the heat pump when the air temperature is 2°C. The H2 output capacity really matters if you live in a colder area, especially where the night temperatures go below 5°C but don't often dip below zero. If this is your climate, insist on being told what the H2 output capacity is.

The bigger the H2 output capacity the better. It's optional to have H2 output capacity on energy labels, but we hope makers will adopt it. Where it's available, we include it in our database of specifications.

If the H2 information can't be supplied make sure your contract with the supplier says that you'll get adequate heating during cold nights.

Features

Think about the features you particularly want in your heat pump. These may include:

• Automatic de-icing is vital if you live in a cold area - otherwise, in winter, the pump will stop providing heat because of frost build-up on the outdoor heat-exchanger coils. This is a standard feature on newer inverter models.
  
  
• A timer lets you switch the heat pump on and/or off automatically at certain times. However, there are big differences. A clock-based timer allows you to programme an actual "on" and "off" time, and the times you set remain active until they're cancelled. A 7 (or more) day timer usually allows multiple on and off times.
  
  
• Sleep mode adjusts the temperature in several steps (up when cooling, down when heating) so that the system works less hard and more quietly when you're sleeping. You can programme how long you want the sleep mode to operate.
  
  
• Airflow-control settings provide reduced airflow for quiet operation and/or extra-high airflow (may be called fast or jet operation). Ideally, you want your heat-pump/air-conditioner to have a big range of airflow settings. A high airflow will help distribute the air in a room more quickly - but the higher the airflow, the noisier and draughtier it is. So you want a low fan-setting that circulates the air but does so quietly, especially if you're using the inside unit in your bedroom.
  
  
• Oscillating louvres allow the air to be distributed more evenly.
  
  
• Adjustable louvres can be pointed up for cool air and down for warm. Left and right adjustability helps direct air where it's needed.
  
  
• Fan-only mode blows air without heating, cooling, or drying. This can provide adequate cooling at some times of the year, without the cost of running the heat pump.
  
  
• Restart delay is a protective feature that prevents the heat pump from starting up again too soon after being switched off.