The short answer: most NZ bedrooms are well served by a 2.0 to 3.5kW heat pump, while a living room or open plan space usually needs 5.0 to 7.0kW, and a whole home or large open plan often calls for 9.0kW or a multi split system. Getting the capacity right is the single most important decision you will make, because an undersized unit runs flat out and never quite warms the room, while an oversized one short cycles and wastes power. This guide walks through the sizing in four steps, then matches each step to a Midea model and a real price.
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Step 1: Size the room in kW
Heat pump capacity is measured in kilowatts (kW) of heating and cooling output. The right number depends on the floor area, the ceiling height, how well the room is insulated, and how much glazing it has. A common NZ rule of thumb is to allow roughly 0.10 to 0.15kW of heating capacity for every square metre of a living space, then adjust up for high ceilings, large windows, or a poorly insulated older home. Treat this as a starting point rather than a final figure, because a proper in home assessment accounts for the details a rule of thumb cannot.
| Room | Approx floor area | Suggested capacity | Midea model (from, supply only) |
|---|---|---|---|
| Small bedroom, office, nursery | Up to about 25 m² | 2.0 to 2.6kW | Midea EF 2.15kW from $849, All Easy Pro 2.6kW from $949 |
| Master bedroom, small living room | About 25 to 40 m² | 3.5kW | Midea All Easy Pro 3.5kW from $1,049 |
| Living room, medium open plan | About 40 to 60 m² | 5.0kW | Midea All Easy Pro 5.0kW from $1,399 |
| Large living, open plan kitchen and lounge | About 60 to 80 m² | 7.0kW | Midea Aurora 7kW from $1,699 |
| Whole open plan, or one big room | 80 m² and above | 9.0kW or more | Midea Aurora 9kW from $2,199 |
| Several rooms from one outdoor unit | Multiple zones | Multi split system | Midea Multi Split 10.5kW from $3,699 |
Key points from step one:
- Match kW to the room, roughly 0.10 to 0.15kW per square metre for living spaces.
- Add capacity for high ceilings, large windows, and older homes with less insulation.
- Use this as a guide, then confirm with an in home assessment for the final size.
Step 2: Choose the right type of heat pump
Once you know the capacity, the next choice is the type of system and the series that suits the room. For a single room, a high wall split system is the usual pick: one indoor unit on the wall paired with one outdoor unit. Midea offers several high wall ranges at Midea Homes NZ, and they differ mainly in features rather than the core job of heating and cooling. The All Easy Pro range is the practical everyday choice with Wi-Fi control across common sizes, the Infini and Aurora ranges add refinement and larger capacities, the Gaia range builds in air purifying, and the Breezeless range focuses on draught free comfort. Mitsubishi Heavy Industries units are also stocked for buyers who want that brand.
If you want to heat several rooms but only have space for one outdoor unit, a multi split system connects two or more indoor heads to a single outdoor unit, such as the Midea Multi Split 10.5kW. It costs more up front but tidies up the outside of the house and suits homes where a separate outdoor unit per room is impractical.
- A single high wall split suits one room, which covers most NZ heat pump purchases.
- A multi split heats several rooms from one outdoor unit, at a higher up front cost.
- Pick the series for the features you want, since all of them deliver the core heating and cooling.
Step 3: Check efficiency and running costs
A heat pump is one of the more efficient ways to heat a NZ home because it moves heat rather than generating it, delivering several units of heat for each unit of electricity. The efficiency figure to look for is the coefficient of performance, or COP, where a higher number means more heat per dollar of power. Modern inverter models, which all of the Midea high wall ranges use, adjust their output continuously to hold a set temperature rather than switching fully on and off, which keeps running costs down and comfort steady.
Running cost in practice depends on the unit efficiency, how large the space is, the temperature you set, and how many hours you run it. Sizing correctly matters here too, because an oversized unit that short cycles and an undersized unit that runs flat out both cost more than a right sized one. For independent NZ guidance on heat pump efficiency and running costs, the EECA Energywise heat pump guide is a reliable reference.
- Look for a higher COP for more heat per unit of electricity.
- Inverter models hold a set temperature efficiently rather than cycling on and off.
- Correct sizing keeps running costs down as much as the headline efficiency does.
Step 4: Factor in installation
Heat pump prices come in two forms, and it pays to know which you are looking at. A supply only price covers the unit itself, which suits buyers who have their own installer or are replacing an existing system. A supply and install price includes professional fitting, which is what most households want for a first heat pump. At Midea Homes NZ many models are offered both ways, so a unit listed from $1,049 supply only will have a higher supply and install price alongside it. Installation involves electrical and refrigerant work, so it must be carried out by a suitably qualified and licensed installer, and correct placement of both the indoor and outdoor units affects how well the system performs.
- Decide between supply only and supply and install before comparing prices.
- Installation is specialist work for a qualified, licensed installer.
- Placement of the indoor and outdoor units affects comfort and efficiency.
Common mistakes to avoid
Most heat pump regret comes down to a handful of avoidable errors. Buying on price alone and undersizing the unit is the most common, and it leaves you cold on the worst winter nights. Oversizing is the opposite trap, where a unit that is too large for the room short cycles, which is less efficient and less comfortable. Forgetting about the room itself is another: no heat pump overcomes an uninsulated room with single glazing and open doors, so insulation and draught stopping make any unit work better. Finally, matching the series to habits matters, whether that is quiet running for a bedroom, air purifying for allergies, or Wi-Fi control so the room is warm before you get home.
- Do not undersize to save money, and do not oversize either.
- Support the heat pump with insulation and draught stopping.
- Choose the series features that match how you actually live.
Frequently Asked Questions
What size heat pump do I need for a living room in NZ?
A typical NZ living room of around 40 to 60 m² is usually well matched to a 5.0kW heat pump, while a larger open plan kitchen and lounge of 60 to 80 m² generally needs 7.0kW. If the room has high ceilings or a lot of glazing, size up rather than down so the unit is not working at its limit on cold nights.
Is it better to oversize or undersize a heat pump?
Neither extreme works well. An undersized unit runs constantly and struggles to reach temperature, while an oversized unit short cycles, which reduces efficiency and comfort. Aim for the right size for the room, and only round up slightly when the space is hard to heat, for example with high ceilings, large windows, or limited insulation.
How much does it cost to run a heat pump in NZ?
Running cost depends on the unit efficiency, the size of the space, the temperature you set, and the hours you run it, so there is no single figure. A correctly sized inverter model with a high COP is one of the cheaper ways to heat a room, and holding a steady, moderate temperature costs less than large swings. The EECA Energywise heat pump guide is a good NZ reference for typical costs.
Can one heat pump heat my whole house?
A single high wall unit heats the room it is in and, to a lesser degree, spaces that open directly off it. To warm several separate rooms you either need a unit in each, or a multi split system that runs two or more indoor heads from one outdoor unit. Open plan homes are easier to heat from one larger unit than homes divided into many closed rooms.
Should I also consider a dehumidifier?
Often, yes. A heat pump warms the air and reduces condensation, but in a damp NZ home a dehumidifier tackles moisture directly, and the two work well together through winter. If damp is a concern in your home, see our guide on what size dehumidifier you need.
Get the right kW for your room. Compare capacities, series and prices across the full Midea heat pump range at Midea Homes NZ, or start with the popular All Easy Pro series for everyday value.