High-wall heat pumps for Wellington homes

Three questions decide whether a high-wall works in a Wellington house, and none of them is which brand you buy. Has the room been given enough capacity for how fast it loses heat. Will it be run in the way that actually dries the place out. And can the outdoor half go somewhere sensible on the section you have, which on a hillside is a real question rather than a formality.

How much does a high-wall heat pump cost in Wellington?

The figures below are for the finished job, including GST. If you see a cheaper number somewhere, it'll be for the unit alone and the fitting comes on top of it.

A small 2.5kW unit for a bedroom, study or small room runs about $2,000 to $2,800. A mid-size 5 to 6kW unit for an average lounge or open-plan area is roughly $2,800 to $4,200, and a large 7 to 8kW unit for a big or south-facing living area $3,800 to $5,500.

The unit is the smaller part of it. What separates one quote from another is nearly always the install.

If the outdoor unit can go straight through the wall behind the indoor head, that's the cheapest run there is. Take it round the house, up into the roof space or concealed inside a wall and it costs more in both time and materials. Working at height on a steep section, or fixing to cladding that won't take a bracket easily, adds hours again.

Then the wiring. A new dedicated circuit or a switchboard upgrade adds cost, though plenty of installs just use the capacity that's already there.

Put your own room through the sizing calculator for a capacity and a price, or read the installation cost page for what separates a cheap quote from a fair one.

Sizing a high-wall heat pump for an older room

A lot of Wellington housing is older timber and single glazed, and it's sitting in the path of the southerly. Rooms lose heat about as fast as a unit can put it back in, which is why the capacity deserves more of your attention than the brand does.

A south-facing lounge in a 1920s villa needs noticeably more than the same floor area in a newer, well-insulated townhouse. The published guide is 2.5kW for a bedroom or study, 5 to 6kW for an average lounge, and 7 to 8kW for a large or south-facing living area, and an older or more exposed room needs the higher figure.

Both mistakes get you, in different ways. An undersized unit runs flat out and never quite wins the room. An oversized one reaches temperature fast, shuts down, and leaves the moisture behind, so it dries the air poorly and costs more than it should. The room ends up warm and still clammy.

Your installer settles the figure on site against floor area, ceiling height, glazing, insulation and which way the room faces.

Will a high-wall heat pump help with the damp?

The complaint here is usually as much about damp as cold. A heat pump does real work on that, but only if it's run the way that dries a house rather than the way that heats it in bursts.

Leave it ticking over on a modest setting through the evening instead of blasting it and switching it off. Held that way it works on the moisture continuously and keeps wall and window surfaces above the point where condensation forms, which is what stops the mould rather than the raw temperature does.

That's also the argument against buying big to be safe. The oversized unit is the one that leaves your windows fogged.

Siting a high-wall heat pump on a steep section

Inside, the head wants to face down the long axis of the room with nothing in front of it. Aimed into a doorway or across the back of a sofa it warms the first two metres, decides the job is done and stops.

Outdoors is where Wellington gets particular. A unit at ground level on a wall bracket is straightforward. On the steep sections through the western hills and the eastern bays, the sensible position is often up at height or on difficult cladding, which is labour rather than a problem, and it's worth knowing that before the quote rather than after.

Out through Lyall Bay, Island Bay, Seatoun and the exposed eastern coast, salt is the other factor. Salt attacks the thin aluminium fins on the outdoor unit, so a corrosion-resistant model is worth specifying rather than taking the standard finish, and the unit belongs on the sheltered side of the house rather than the elevation facing the water. Inland through the valleys it stops mattering.

Three things make a position workable anywhere: clear air on all sides, height off the ground, and a drain path for the condensate. A fourth is worth adding in this city, which is somewhere a technician can actually stand, or the annual service turns into a scaffolding job.

One high-wall heat pump, or several?

One unit in the main living area with the internal doors open carries a surprising amount of a compact house, and for one or two living spaces that's often all that gets fitted.

Where you want the bedrooms done as well, a multi-split runs several indoor heads off one outdoor unit. That matters more here than it sounds: on a steep or exposed section it means one outdoor position to get right instead of three. A ducted system hides the lot and heats every room evenly, at the top of the price range.

A high-wall is also reverse-cycle, so the same box cools in summer. Wellington summers are mild, but a north-facing top-floor room or a west-facing lounge still gets uncomfortable, and there's nothing extra to buy for it.

Weighing it against something else? The types of heat pump page sets a high-wall beside floor consoles, multi-splits and ducted whole-home systems, while heat pump installation covers what the job involves and what moves the price. Get a free quote when you want a number.