What size heat pump do I need?
Multiply the floor area by 0.13 kW per m² for a room with ceiling and underfloor insulation and a 2.4 m stud, then adjust for a higher stud, less or more insulation and a cold climate. A 25 m² insulated lounge in Auckland comes to about 3.3 kW. The calculator shows the working and the package that fits.
| 25 m² × 0.13 kW | 3.3 kW |
|---|---|
| Stud 2.4 m | — |
| Insulation: some | — |
| Auckland: mild | — |
| Sized for | 3.3 kW |
Small room package: a 2.5, 3.5 or 4.2 kW high-wall unit, standard back-to-back install and electrical certificate. We're contracting the installer for Auckland, so bookings go on the waitlist for now.
A rule of thumb, shown so you can check it. Our installer's site check confirms the size before you accept the price. How the method works.
From kW to a package
| Calculator result | Package | Unit fitted |
|---|---|---|
| Under 4.5 kW | Small room | 2.5, 3.5 or 4.2 kW high-wall |
| 4.5 to 7 kW | Living area | 5.0, 6.0 or 7.1 kW high-wall |
| 7 to 10 kW | Large open plan | 8.0 or 9.0 kW high-wall |
| 10 kW or more | Custom quote | Multi-split or ducted |
The adjustments
| Factor | Adjustment |
|---|---|
| Stud above 2.4 m | +12% per 0.3 m |
| No insulation | +35% |
| Ceiling and underfloor insulation | No change |
| Plus wall insulation and double glazing | −15% |
| Building Code H1 zones 5 and 6 | +20% |
What size heat pump do I need for a 30 m² room?
About 3.9 kW in a mild or moderate climate with ceiling and underfloor insulation and a 2.4 m stud, and about 4.7 kW in Christchurch, Dunedin or further south.
How does the calculator work?
Floor area × 0.13 kW per m², then +12% for every 0.3 m of stud above 2.4 m, +35% with no insulation or −15% with walls insulated and double glazing, and +20% in Building Code climate zones 5 and 6. The full method is in our sizing guide.
Is 0.13 kW per m² an official standard?
No. It's a rule of thumb, shown so you can check it. The Building Code climate zones come from MBIE's H1/AS1, and Consumer NZ also says to size up for high ceilings. Our installer's site check confirms the size before you accept a price.
What if the calculator says 10 kW or more?
That's more than one high-wall unit should heat. Insulating first often brings it down. Otherwise a multi-split or ducted system suits, on a custom quote.
I'm a landlord. Can I use this for Healthy Homes?
No. Use the official Tenancy Services Heating Assessment Tool for the main living room of a rental. See our rentals guide.
Tell us the room. We'll tell you the size, the price and exactly what's included.
Size the room in two minutes. You see the kW, the package it needs and the standard install spelled out. Ducted, several rooms or a tricky wall? Ask for a custom quote.