A heat pump needs to be the right size for the area it’s going to heat.
Join more than 100,000 members today and you’ll get:
Too small means the unit will have to work so hard that it won’t deliver its best efficiency and will be slow at heating a cold room. It’s also more likely to freeze up in very cold weather. Too large means the unit will have to cycle on and off to avoid overheating the area. It’ll also cost more to buy than a model that’s the right size.
Get the size right and the heat pump will operate somewhere in the middle of its heat-output range – and that’s where it’s most efficient.
Once you know the size, get the most efficient model you can find.
Red = external wall
Blue = internal wall
A x B = area of wall
C x D = area of window
E x F = area of ceiling to unheated/heated room above
G x H = area of ceiling to un-insulated roof
Use our calculator to work out what size heat pump will best suit your needs.
Example: A well-insulated bedroom 3m x 4m x 2.4m high has a volume of 28.8 cubic metres. Multiply by 44 to get 1267 watts, and again by 1.2 to get 1520 watts (1.5kW).
Compare heat pump reviews and specifications in our product database, plus find out more about choosing the best heat pump for your needs.
Stay in the know with what’s new. Information about our latest tests, investigations and advocacy campaigns delivered to your inbox weekly.
Thanks for requesting to reset your password. We've sent you an email with instructions on what you need to do. If you haven't received the email within the next five minutes please call us on 0800 266 786.
Sorry, the information you are trying to access is available to paying members only. Your membership helps us deliver our services and advocate for a fair deal for all New Zealand consumers.
Not a member yet? Avoid expensive mistakes and join more than 80,000 other savvy consumers making smart decisions.