Things to consider when sizing a heat pump for your home.

Are you wanting to heat just one room or your whole house, There are many different configuration of units from the High Wall split unit to a cassette that mounts into the ceiling space, a floor console which mounts onto a wall down low or a ducted system for part or all of your house.

3°C average lowest winter temperature for the Northland Region

For your heat pump to work effectively year-round it must be rated* at an outside temperature of 3°C to give you a heating requirement. This takes into consideration how your heat pump will perform in the winter conditions in your specific region. These temperatures are based on annual temperature reports. (*Heat pumps are normally rated at 7°C)

Some thoughts for a High wall split system

Location, Location, Location:

The better location is on the long wall of the room, this minimises any dead air spots in the room allowing for better heat distribution. The indoor unit normally needs 100mm clearance from the ceiling to allow for air flow, some units can require less but we would need to check these out for you.

Try and locate the indoor unit on an outside wall, this allows for ease of installation to the outdoor unit. There are pipes and cables that need to be installed between the indoor and outdoor unit, These will normally go through a 65mm hole in the wall so sighting the indoor unit will need to allow for this. Indoor units can be mounted on inside walls but this will require extra components to be fitted to remove any condensate and hence extra cost and access to the ceiling space needs to be considered, give us a call if in doubt.

Things also to consider if required to be mounted on an internal wall, is there a cupboard or wardrobe behind that wall, can this be used to bring the pipes and cables through and up to the ceiling space or down to under the house to then run to the outdoor unit. Two story house?, Not a problem if on an outside wall but we may need to scaffold up to get to the penetration to the indoor unit, give us a call to check

How BIG is my room:

Size your room and allow for any entrances that don’t have a door on them to be included; ie they share the same air as the room that the unit is located, This needs to be taken into the calculation.


How many windows in the room. The more glass the more the heat loss so maybe a bigger unit is required.


Do you have good insulation in the roof, walls and under the floor, is there double glazing. If you don’t then the heating factor needs to change.

Electrical switchboard:

Do you have room in the switchboard to allow for an extra circuit if needed. Some small units can be connected to existing power circuits, however this would need to be checked on site so as not to overload any circuit.

Condensate water:

Indoor and outdoor units have condensate water accumulate on the coils which needs to be drained away, consider where this is to be drained to. On a concrete path will lead to it becoming slippery, into a garden or down a drain is best.

Site visit:

If you’re unsure or need some more information, give us a call, one of our experienced team will happily talk you thru your requirements or we can come to your house and check out the best place to install your new heat pump at no charge

Rule of thumb for sizing

Room length by width by height, times insulation (multiply factor either 0.55 for good insulation or 0.65 for poor insulation) then divide by 10 to give an approximate heating kilowatts for heat pump sizing

Eg: 4 mtrs x 3 mtrs x 2.4 mtrs x 0.55 = 15.84 /10 = 1.58 or 1.6Kw heating capacity

Pricing is for a back to back installation of $850 with a 5 metre pipe connection on an outside wall, excluding the heat pump. For every metre after that, an additional $75, all excluding GST and travel. We maintain the right to check the installation and adjust the price according to suitability of installation location.

Enter your room dimensions in the form below and we will get back to you with an approximate quote.

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