Choosing the right sized heat pump is important to ensure optimum comfort levels; particularly when outdoor temperatures drop. Location, room size, and insulation levels in a room are all factors that determine which heat pump size should be installed.

Insulation and building orientation are key factors which can influence the degree of heat loss in a home. An older style home with poor insulation will lose indoor heat at a faster rate than a modern well-insulated home that faces north. The quicker a home loses heat, the bigger the heat pump system will need to be to overcome this heat loss.

Outdoor ambient conditions in winter also play a big role in unit size selection. When temperatures drop, the output capacity of the heat pump also drops. Areas of New Zealand that experience sub-zero temperatures in winter will require either a larger capacity heat pump or an upgrade to a Mitsubishi Electric HyperCore^® Heat Pump, in comparison to a same sized room in a warmer region. It is therefore very important that units are not undersized in low ambient conditions.