Getting the Most From Your Heat Pump's Cooling Mode

Most New Zealand cooling advice starts from the wrong assumption: that you’re deciding whether to buy something. For a large majority of Kiwi households, that decision is already made — you likely have a heat pump, bought primarily to heat the house through winter, with cooling as a feature you may not be using well, or at all.

Most homes already have one

As of the 2023 Census, 66.8% of New Zealand dwellings now rely on a heat pump as their main heating source — up from 47.3% in 2018, and just 21% back in 2009. That’s a fast, genuine shift in how New Zealand homes are heated, and it means the realistic starting question for most readers isn’t “should I buy a cooling appliance,” it’s “am I actually using the cooling side of what I’ve already got.”

Getting cooling mode right

A heat pump left on the wrong settings in summer either underperforms or costs more to run than it needs to. The fixes are mostly free:

• Use “Cool” mode specifically, not “Auto” or “Dry.” Auto mode decides for itself whether to heat or cool, which can work against you; Dry mode prioritises removing humidity over actually lowering the temperature.
• Set it to 24–27°C, not as low as it goes. A heat pump cools at a fixed rate regardless of the target temperature — setting it to 18°C doesn’t cool the room faster, it just means the unit runs longer to reach an unnecessarily cold target and uses more power doing it. Each degree you raise the setting can cut running cost meaningfully, often cited around 10% per degree in hot weather.
• Close doors and windows while it’s running. Heat pumps are built to condition a sealed space. If warm outside air keeps leaking in, the unit never actually catches up — this is the single most common reason a heat pump “doesn’t cool the room properly” when the real issue is an open door down the hall.
• Clean the filter before summer starts. A clogged filter makes the unit work harder for less output, in both heating and cooling mode — a five-minute job that’s easy to forget once winter heating season ends.

When your heat pump genuinely isn’t enough

Two situations come up often enough to be worth naming honestly:

It doesn’t reach the room that needs it. Many heat pumps were installed for winter heating in a living area, and were never intended to cool every bedroom in the house. If that’s your situation, a second heat-pump installation is a big, installer-quoted job — a portable air conditioner or a good fan covering just that one room is the realistic lower-cost fix, not a downgrade.

It’s undersized for the room it’s in, or the room gets serious direct sun. A heat pump sized for winter heat output isn’t automatically well-matched for summer cooling load in the same room, especially somewhere with a lot of west-facing glass. If it’s running constantly without quite keeping up, that’s a sizing issue worth checking rather than a settings problem.

For either case, see the products on this page for real, verified options — a portable unit for a room that needs proper cooling capacity, or a fan for supplementary airflow. Our room-size calculator can also tell you honestly whether what you’ve already got should be enough, before you spend anything.