Free 60-second sizing check
Heat pump sizing calculator
Not sure what size heat pump you need? Answer four quick questions and we'll suggest a size, system type and price range, sized the way we'd size it for a cold, damp Wellington home.
What are you trying to heat?
How big is the space, roughly?
Rough is fine. If in doubt, go up a size.
How old is your home?
Older homes are less insulated and need more capacity.
Sun and exposure?
In Wellington, south-facing and exposed rooms stay colder.
Your suggested starting point
Indicative supplied and fitted, incl GST.
Why this size
This is a guide, not a quote. A calculator can't see your ceiling height, insulation or exact aspect. The accurate figure is a free on-site visit and a written quote.
Get your free quote
We'll bring your answers along, so we already know your situation before we call.
Most Wellington rooms land on a 2.5kW unit for a bedroom, 5 to 6kW for an average lounge, and 7 to 8kW for a large or south-facing living area. Older, draughty or low-sun rooms usually want a size up. To heat the whole house you're into multi-split or ducted territory.
Why getting the size right matters
Size is the single biggest thing that decides whether a heat pump keeps you warm cheaply or quietly disappoints. It's worth a minute to get it close, because the wrong size costs you either way.
Too small and the unit runs flat out on the coldest days, never quite reaching temperature, costing more to run while it wears itself out faster. Too big and you've paid upfront for capacity you don't use, and an oversized unit short-cycles, heats unevenly and dries the air poorly.
The right size sits in the sweet spot: enough grunt for the coldest Wellington mornings, running efficiently for most of the year. That's the cheapest way to stay warm over the life of the unit. If you want to see how size feeds into price, our heat pump installation cost guide breaks down the ranges, and the main heat pump types page covers which setup suits which job.
Heat pump size guide for Wellington homes
These are indicative supplied-and-fitted ranges for greater Wellington in 2026. Your home could sit anywhere in a range depending on ceiling height, insulation and aspect.
| Space | Suggested size | System | Indicative price |
|---|---|---|---|
| Small room (under 20m2) | 2.5kW | High-wall split | $2,000 to $2,800 |
| Average lounge (20 to 40m2) | 5 to 6kW | High-wall split | $2,800 to $4,200 |
| Large or south-facing living (40 to 60m2) | 7 to 8kW | High-wall split | $3,800 to $5,500 |
| Under windows or fire replacement | 2.5 to 6kW | Floor console | $3,000 to $5,500 |
| Two to three rooms | Multi-head | Multi-split | $5,000 to $9,500 |
| Four or more rooms | Multi-head | Multi-split | $9,000 to $13,000 |
| Whole home | 10 to 16kW | Ducted | $12,000 to $25,000+ |
Ranges are a guide for 2026 and are not a quote. For whole-home options, see our ducted heat pumps in Wellington page.
Common questions about heat pump size
What size heat pump do I need for a bedroom?
Most Wellington bedrooms under 20m2 are well served by a 2.5kW high-wall split. If the room is older, faces south or is exposed to the southerly, it's worth stepping up to the next size so it isn't running flat out on a cold night.
Does a south-facing Wellington room need a bigger heat pump?
Often yes. South-facing and exposed rooms lose heat faster and get little winter sun, so for the same floor area we'll usually size up a notch compared with a sunny north-facing room. Getting that call right is the difference between a warm room and one that never quite catches up.
Can one heat pump heat a whole house?
A single high-wall heats the room it's in, not the whole house. To warm most or all of a home you're looking at either a multi-split, one outdoor unit running several indoor heads, or a ducted system that heats every room from one hidden unit.
How accurate is this heat pump sizing calculator?
It gives a solid starting point from the things that matter most: room size, the age of the home and how much sun and shelter it gets. It can't see your ceiling height, insulation or exact aspect, so treat it as a guide. The accurate figure comes from a free on-site visit and a written quote.
The calculator is a guide. The site visit is the answer.
We'll measure up properly, factor in your insulation and aspect, and give you an accurate quote with no obligation.