Once the lounge is warm, the next question is usually the bedrooms. You have three ways to heat more than one room with heat pumps, and each has a catch.
- A single-room heat pump: one indoor unit, one outdoor unit, one room.
- A multi-room system (also called a multi-split): one outdoor unit running several indoor units.
- Several single systems: a separate indoor and outdoor unit for each room.
Ducted heating is a fourth option, with one hidden unit and ducts to every room. It gets a full comparison in ducted vs high-wall heat pumps.
When is one single-room heat pump enough?
This is what most Kiwi homes have. One indoor unit, usually a high-wall, heats one room, piped to one outdoor unit on the nearest outside wall. It works best in the main living area of an open-plan home, where the warmth can spread.
Good for: the main living space, a budget that covers one unit now, a house where you only use one room much in winter.
The catch: it heats one space. A high-wall in the lounge won’t warm the bedrooms at the far end of a hallway, however hard it runs. If you need more rooms warm, you’ll end up choosing between options 2 and 3 anyway.
→ Related: How to size a heat pump for your home
What is a multi-room heat pump system?
A multi-room system has one larger outdoor unit piped to two or more indoor units. Each indoor unit has its own remote, so you can set a different temperature in each room or turn one off.
How many rooms depends on the outdoor unit. Some are made for two rooms. Others take five, and Mitsubishi Electric’s multi-room outdoor units take between two and eight indoor units, depending on the size.
You can mix the indoor types. A quiet small high-wall in a bedroom, a floor console in the study and a ceiling cassette in an open-plan kitchen can all run off one outdoor unit.
Why people choose multi-room
- One outdoor unit instead of several. That matters on a townhouse with a small yard, a narrow section in Wellington, or a house where the only outside wall space is under a bedroom window.
- It’s usually cheaper than buying several separate systems, because there’s one outdoor unit to buy, install and service.
- You can grow it. Some systems let you connect only some of the indoor units at first. A four-room system could start with two indoor units and add the other two later, all on the same outdoor unit. That only works if you plan for it on day one and pick an outdoor unit big enough.
→ Related: Single room and multi room heat pumps compared
What are the downsides of multi-room?
- One mode at a time. Every indoor unit has to be in heating, or every one in cooling. You can’t cool a hot north-facing office while heating a cold south-facing bedroom. Each room can still have its own set temperature.
- Shared capacity. The outdoor unit has a set amount of heating to share. Its size decides how many rooms, and how big, it can heat at the same time. If everyone turns their room on at once on a frosty Canterbury morning, each room gets its share, not a unit’s full output.
- Longer pipe runs. Each indoor unit needs its own pipes back to the one outdoor unit. Longer runs can add to the installation cost.
- More eggs in one basket. One outdoor unit serves every room on the system, so if it stops, they all stop.
- Fewer features on some models. For example, Mitsubishi Electric indoor units lose their energy monitoring when they’re connected to one of its multi-room outdoor units, although wi-fi control still works.
Is it better to have several single-room heat pumps?
The other way is a separate single-room heat pump in each room, each with its own outdoor unit.
Why people choose it:
- Each room is independent. One room can cool while another heats. If one system breaks, the others keep going.
- You can add rooms whenever you like, with no need to size an outdoor unit for the future.
- Each unit is sized for its room and runs on its own.
The trade-offs:
- An outdoor unit for every room. Four rooms means four outdoor units on the outside walls. Each one needs clear air around it, a solid base or bracket, and a spot where its noise won’t bother you or the neighbours.
- More to buy and install overall than one multi-room system doing the same job.
- More to service. Every outdoor unit needs keeping clear, and every system needs its own yearly check. Our guide on heat pump servicing covers what that involves.
→ Related: What heat pump noise rules mean for neighbours
How to choose between single-room and multi-room
Start with how you live in the house.
- Mostly in one open-plan space? A single well-sized unit in the living area is often all you need.
- Want two to five rooms warm, with little outside wall space? A multi-room system keeps the outside tidy.
- Rooms that want heating and cooling at the same time, like a sunny office and a cold bedroom? Separate systems handle that; a multi-room system can’t.
- Building or renovating with the ceiling open? Look at ducted as well.
Whatever you lean towards, have an installer come and look. They need to size each room, find where the pipes can run, and check where the outdoor unit or units can go. Our guide on what size heat pump you need helps you check their numbers.
Where to find a multi-room heat pump installer
Browse installers who fit multi-room systems or high-wall units, or pick your town to see who works near you.