Heat Pump Sizing Calculator for Invercargill Homes
Punch in your room size and how tight the house is, and you'll get a rough kW range. It's a starting point, not the final word. We measure up before we quote.
What are you heating?
How big is the space?
How old is the home?
Sun and exposure in winter?
Our suggestion for your home
This is a guide based on your answers, not a fixed quote. The real answer is a free site visit, where we measure the rooms, check the insulation and confirm the size and price for your home.
Get your sized quote
Send us your details with your calculator result attached and we'll come back with honest options and a fixed price for your home.
As a rough guide, size a heat pump at about 0.10 to 0.15 kW per square metre for a warm, well-sealed Invercargill room, and more for a draughty villa. A 40m2 lounge usually lands around 5 to 6kW here. Always get it measured before you buy.
What the calculator actually measures
Start with the floor area of the room. Length times width in metres gives you the square metres. Then think about how the room's built: single or double glazing, how much of the wall is window, whether the ceiling is high, and if it's insulated.
A sealed 30m2 lounge with double glazing might only want a 4kW unit. The same size room in an old villa with single glazing and a gappy floor can need 5 to 6kW to hold the same warmth on a frosty morning. That's why area alone never gives you the answer.
Why Southland numbers run higher than the rest of the country
Most online calculators are set for Auckland or Wellington. Invercargill is a good deal colder, so a heat pump here works harder for longer through winter. If you size off a national chart you'll often end up short, and a unit that's short runs flat out on the coldest days and still can't keep up.
Homes in the valley and coastal cold pockets around Richmond and Strathern get low winter sun and stay damp and slow to dry. Those rooms need a bit more grunt again. When we work out heat pump installation cost, the right size is the first thing we lock in, because guessing it wrong costs you either way.
Sizing an old villa vs a newer Waikiwi build
Invercargill's older single-glazed villas leak heat through the windows, floors and ceilings. They need generous sizing to feel warm, and often a wall unit with strong low-temperature output. Newer sealed builds hold their heat, so a smaller unit does the job and sips less power.
If you've recently put in double glazing or ceiling insulation, tell us. It genuinely changes the kW you need, sometimes by a whole unit size. The right types of heat pump for a villa aren't always the ones that suit a tight modern home.
Heating one room or the whole house
The calculator works room by room. If you want warmth through the lounge, hallway and bedrooms, don't just add the numbers up and buy one huge unit. A single big head in the lounge won't push heat down the hall to the bedrooms in Windsor or Grasmere.
For several rooms off one outdoor unit, look at multi split heat pumps. We'll map out which rooms you actually use and size each head to the space, then sort the heat pump installation in Invercargill around your home's layout.
Common questions about heat pump sizing
What size heat pump do I need for my room?
It depends on the room's floor area, glazing and insulation, not just the size. As a rough Invercargill guide, a 20m2 bedroom often suits a 2.5 to 3.5kW unit, and a 40m2 open-plan lounge around 5 to 6kW. A draughty single-glazed room needs the higher end. We measure up before giving a firm answer.
How many kW of heating do I need per square metre?
For a warm, well-sealed Invercargill room, plan on roughly 0.10 to 0.15 kW per square metre. For an older villa with single glazing and poor insulation, push closer to 0.15 or above. These are starting figures. Ceiling height, window area and how cold your pocket of town gets all shift the number.
Is a bigger heat pump always better?
No. An oversized heat pump costs more to buy, then short-cycles, blasting hot then switching off before it dehumidifies the air. That leaves the room feeling stuffy and damp, and wears the unit faster. The right size runs steadily and keeps the room even, which matters through a long Southland winter.
How does insulation affect heat pump size?
A lot. Good insulation and double glazing keep heat in, so a smaller unit holds the room warm. A single-glazed villa loses heat fast, so it needs a bigger unit to match. If you've upgraded glazing or ceiling insulation lately, tell us, because it can drop you a whole unit size.
Get a size that fits your home
Give us a call on 03 244 7345 or send your room details through. We'll size it right for your place, whether you're in Heidelberg, Strathern or anywhere across Invercargill.