What size heat pump do I need in NZ?

The simple answer is the size that will heat your home most efficiently. Achieving the greatest efficiency means understanding your specific requirements and tailoring a heat pump system to fit, whether it’s a single room or an entire house.

The optimal size for a heat pump is defined by the space(s) that it’s intended to heat. The first thing to understand is that bigger is not necessarily better, and that there are many other factors to consider before deciding what size heat pump you will need.

Doing the calculations

Even though there are several online tools and charts for calculating the size of heat pump you will need in NZ, the actual calculation isn’t necessarily a simple exercise, mainly because of the large number of variables involved.

Calculations are based first on room size, which is easy to establish. Multiplying the room’s volume by 55 watts provides the total watts needed to heat it and therefore the size of heat pump you will need. For example, a standard room of 5m x 5m x 2.4m = 60m 3, which is then multiplied by 55 to give a total of 3300 watts.

This indicates you would need a 3.3kW heat pump to heat the room efficiently. But the calculation doesn’t take into account the characteristics of the room: whether it’s new or old, sealed or draughty, well insulated, double or single glazed, and so on. Nor does it factor in the local climate, average seasonal temperatures, or whether the room gets a lot of direct sunlight.

Standalone or multi-room

Another important factor when deciding what size heat pump you’ll need is whether it is a standalone unit for a single room or part of a larger system. Heat pumps come in four main types – wall-mounted, floor consoles, multi-room systems and ducted central heating – each of which will suit a different application, depending on the size and number of rooms you wish to heat.

Of course, the efficiency of your home insulation will have a major effect on the heat pump, which will have to work much harder to compensate for the heat loss from poorly insulated rooms. Both under- and overpowered heat pumps, which can experience ‘short cycling’ as a result of rapid temperature increase, will lead to inefficiencies and increased costs.

Choosing a local supplier

Finally, the size of heat pump you need in NZ will depend in part on the local climate.
Temperatures in Canterbury can often dip below the 7°C threshold below which heat pumps comfortably operate, meaning the system must work harder to produce the same amount of energy.

Rather than attempt to make all these calculations yourself, we suggest you consult an experienced local heat pump supplier, who will visit your home and look at all the relevant factors before advising you on what size heat pump system you will need.

Talk to a heat pump expert at SnowTemp for pricing and options.