31/01/26
Hubby likes to walk around in shorts and a T-shirt all year round. My teenage daughter lives on the couch in a fluffy onesie. And my mother, when she comes to stay, insists her room is set to “slow bake”. Sound familiar?
So when it came to heating our modern 4-bedroom New Zealand home, I quickly realised choosing the right system wasn’t as simple as picking a unit off the shelf. I kept asking myself: What size heat pump do I need?
To get a proper answer, I spoke with the experts at Oxygen Air—and they had some surprisingly flexible (and very practical) solutions.
The first thing they recommended was a full home assessment. And honestly, this step is essential if you’re wondering what size heat pump do I need?
A site visit allows technicians to:
As it turned out, I didn’t just need one heat pump—I needed a tailored multi-room solution.
One of the most important factors is simple: room size.
As a general guide for modern, well-insulated homes in New Zealand:
This rule of thumb helps answer the question what size heat pump do I need?, but it’s only part of the picture.
For example, colder regions like the South Island often require higher kW ratings.
A 40m² room that might normally need 4–5kW could require around 6kW+ in colder climates.
Older homes with poor insulation may also need significantly more heating capacity.
So while these figures are a great starting point, they’re not the final answer to what size heat pump do I need?—professional assessment is still important.
In our case, the layout of the home changed everything.
We have:
We originally considered a ducted system, but due to limited ceiling access, it was ruled out early.
That’s when Oxygen Air recommended a multi-room heat pump system, such as the Mitsubishi OmniCore Multi Room System.
This solution uses:
So instead of constantly asking what size heat pump do I need?, the better question became: how do I heat each space efficiently?
We ended up with a 5-room setup:
Because not all units run at full capacity at the same time, a single 10kW outdoor system was sufficient for the entire home.
This made a huge difference in comfort and efficiency.
A multi-system approach solves a common issue in New Zealand homes—everyone wants a different temperature.
Now:
The lounge can be warm and comfortable for family time
Bedrooms can be cooler or warmer depending on preference
Guests (including Mum in “slow bake mode”) are happy
Energy use is more controlled
So again, what size heat pump do I need? doesn’t always mean one big unit—it often means multiple smaller, well-placed systems working together.
Another practical factor is budget.
In our case, we aimed to keep the full installation around $10,000. With the multi-system approach, we were able to achieve a comfortable whole-home solution close to that target (excluding GST).
So the real-world answer to what size heat pump do I need? often includes another question:
What size system fits my budget while still delivering comfort?
If you’re heating a single room, figuring out what size heat pump do I need? is relatively straightforward using room size and kW guidelines.
But for full homes, especially modern layouts like open-plan living, it becomes much more personalised.
That’s why a professional assessment is so important. The team at Oxygen Air helped us map out our home properly, match the right systems to each space, and avoid over- or under-sizing anything.
Because in the end, the real goal isn’t just answering what size heat pump do I need?—it’s making sure every room feels right for the people living in it.
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