High-wall heat pumps for Nelson homes

A high-wall is the right answer for most Nelson rooms, and three things decide whether it's right for yours: how much capacity the room needs to beat a still frosty dawn, whether the warmth has to reach floor level in a high-studded old villa, and how much salt your address gets off the bay.

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

Fitted, a bedroom or small room runs about $2,000 to $2,900. A main living area is $2,900 to $4,400, and a large or open-plan space $3,800 to $5,500. That's roughly 2.5kW, 5 to 6kW and 7 to 8kW of capacity.

Those cover the whole job rather than the box: the indoor and outdoor units, the brackets and mounts, the pipework and cabling between them, the electrical work and the labour to fit it and test it. An advertised price well under that is the unit on its own, with the fitting still to come.

What you actually pay comes down to how hard the job is. The cheapest one is where the outdoor unit can go on the other side of the same wall as the indoor head, so the pipework only has to cross one wall and nothing else. A long stretch of pipework, a hard-to-reach mounting spot or a switchboard with nothing spare on it all push it up.

What else moves it

Out at Tahunanui and Atawhai, and along the coast toward Motueka, a unit built for salt air costs a little more and is worth every cent of it. Inland it makes no practical difference and the money does more good spent on capacity.

The sizing calculator will give you a capacity and a rough figure in about a minute, and the installation cost page explains what shifts a quote.

Why a still frosty morning is the real test

On a windy night the air outside and inside keeps mixing, so the temperature in a room stays fairly even top to bottom. On a still, frosty Nelson dawn nothing is stirring it. The air settles into layers instead, cold and heavy down at the floor, warmer up near the ceiling.

A high-wall puts its warmth into the top of that. The air it blows is warmer than the room, so it wants to stay up rather than sink, and it takes a while to work its way down to where you're sitting. Meanwhile the thermostat, which is inside the unit up on the wall, is reading the warmest air in the room and easing off. That's why a high-wall can feel slow on exactly the morning you wanted it most, and why the floor can stay cold in a room the controller says is up to temperature.

None of that is a fault and it isn't a reason to avoid one. It's a reason to size it properly, run it earlier on a frosty morning rather than blasting it at breakfast, and aim the louvres down rather than straight out.

In a single-glazed villa with a high stud through The Wood or Washington Valley the effect is at its worst, because there's more room above you for the warmth to collect in. That's the case for a floor console instead: it sits low on the wall like a radiator, so the warmth arrives at foot level first and works up. It costs a bit more and needs clear wall space down low, and in that particular house it's the better machine.

Sizing one for a Nelson winter

The published guide is 2.5kW for a bedroom, 5 to 6kW for an ordinary lounge and 7 to 8kW for a large or open-plan space. What decides whether your room takes the step up is how fast it loses heat, not how many square metres it has.

A single-glazed villa through the central suburbs sheds warmth through the windows and the gaps about as fast as a modest unit can supply it, so it needs noticeably more than the same-sized room in a tighter modern build out at Richmond or Stoke.

Undersize it and it runs flat out at six in the morning and never quite gets there. Oversize it and it races the room up, cuts out before it has pulled any moisture from the air, and leaves you warm and clammy. Neither is cheap to run.

Your installer works out the heat loss on site against the glazing, the insulation, the ceiling height and which way the room faces, rather than reading it off the floor plan.

Where the outdoor unit goes

It wants air moving freely around it, a spot up off the ground, and enough room for someone to get at it for the yearly service.

The outdoor unit is a copper coil threaded through hundreds of thin aluminium fins, and those fins are how it sheds heat outside. Near the water at Tahunanui or Atawhai, salt settles on them and works into the metal, and once they've corroded there's less left to shed heat through, so the unit runs longer for the same warmth. Keeping it out of the worst of the prevailing salt, and rinsing it down with fresh water now and then, buys it years.

The other Nelson consideration is noise. It's a quiet city and sections aren't always generous, so an outdoor unit a couple of metres from a bedroom window, yours or a neighbour's, is worth moving at the quote rather than after it's mounted.

Indoors, the head wants a clear stretch of wall with the room opening out in front of it, blowing down the length of the space rather than into a doorway or across the back of a sofa.

Will one heat the whole house?

Leave the internal doors open and a single unit in the lounge reaches more of a small house than you'd guess. For one living space that's generally where the conversation ends.

It won't turn a corner or push heat down a hallway, though. If the bedrooms matter you're choosing between a second unit and a multi-split, which runs several indoor heads off one outdoor compressor. On a smaller Nelson section, or a villa where you'd rather not clutter the side of the house with boxes, that's the tidier answer. It costs more up front than a single unit and the price follows how many heads and how far apart they sit.

For even warmth through a whole home, ducted hides in the ceiling and feeds every room through vents, and a ceiling cassette recesses into the ceiling and blows down across a large open space.

Whatever goes in cools as well as heats, which earns its keep through a muggy Nelson summer afternoon. There's nothing extra to buy for that half of it.

Not decided yet? Types of heat pump lines a high-wall up against a floor console, a ceiling cassette, a multi-split and ducted, and heat pump installation covers how the day runs. For a number on your own room, get a free quote.