Heat Pump FAQs

It depends on floor area, ceiling height, insulation, glazing and orientation. Mitre 10's guide suggests 2.5 to 3.5 kW for rooms up to 20 square metres, 3.5 to 5 kW for 20 to 40, and 5 to 7 kW for 40 to 60. High ceilings and poor insulation push the figure up, so we measure every room before quoting.

No. Consumer NZ says oversized units waste energy and cost more upfront, while undersized units struggle. The right size runs efficiently and holds a steady temperature.

High wall units suit most lounges and bedrooms. Floor consoles suit rooms with large windows or high ceilings. Multi-split systems run several rooms from one outdoor unit, and ducted systems heat the whole house through hidden ducts.

Use the cold zone ratings for New Zealand, compare annual kWh between models of similar capacity, and check the heating output at 2 degrees as well as 7 degrees.

Usually not evenly, unless the home is small and open-plan. Heat does not travel well through doors and hallways, so most homes need a unit per main area or a ducted system.

Yes. Heat pumps sold for homes heat and cool, and most have a dry mode for humid days.

Auckland Council says most residential heat pump installs do not need building consent. Heat pump hot water systems do need consent.

A licensed electrician must connect the unit to the electrical supply, and you should receive an Electrical Certificate of Compliance and an Electrical Safety Certificate.

A standard back-to-back high wall install usually takes a day or less. Multi-split and ducted systems take longer.

Somewhere with good airflow, a short pipe route and service access, as far from neighbours' bedrooms and boundaries as practical. Auckland Council warns badly placed units can exceed noise limits at night.

Usually, with body corporate approval for the outdoor unit and pipe route where they affect common property. Check your body corporate rules first.

Rentals need fixed heating that can bring the main living room to 18 degrees, with heaters of at least 1.5 kW. Heat pumps must have a thermostat, and the required capacity comes from the Tenancy Services heating assessment tool.

Consumer NZ estimates under $200 a year for a small 2.5 kW unit and about $1,000 a year for a 10 kW or larger unit, depending on use and power prices.

Set a comfortable temperature and leave it there, rather than turning it to maximum. A moderate setting uses less power, and the timer can warm the room before you need it.

Use the timer so it runs when you are home and warms the room before you arrive. Consumer NZ suggests timers rather than running the unit all day in an empty house.

Dry mode removes moisture but does not heat, and Consumer NZ says a heat pump cannot heat and dehumidify at the same time. Use it on humid, mild days rather than cold evenings.

Yes. Clogged filters restrict airflow so the unit works harder. EECA advises cleaning filters every few weeks during heavy use.

Clean the filters yourself every few weeks during heavy use and book a professional service every year or two. Coastal and damp homes benefit from an annual service.

Mould and dust inside the indoor unit, usually on the coil and fan. It needs a deep clean, because a filter wash will not reach it.

Usually a blocked or poorly sloped condensate drain, or ice build-up from very dirty filters. A service normally finds and fixes it.

In cold, damp weather the outdoor unit defrosts its coil now and then, which can produce steam and a short pause in heating. Constant icing needs checking.

It may be defrosting, which takes a few minutes. If it keeps blowing cold air, check the filters and settings, then book a repair so we can check the refrigerant system and sensors.

Minor faults on a sound unit are usually worth fixing. If an older unit has a major failure such as a compressor, replacing it with a modern inverter model is often better value.