Heat Pump Cover NZ: Sizes, Materials and Install Guide

The outdoor unit on a heat pump is the part most people quietly resent. It sits on the side of the house, it is plain, and on a coastal NZ site it picks up salt and weather faster than anything else on the cladding. A heat pump cover hides the unit, slows down the corrosion, and reduces the rumble that carries into the lounge or the neighbour’s bedroom. The catch is that a cover done badly can also choke airflow, void the warranty, and shorten the life of the compressor.

This guide walks through how to spec a heat pump cover for a NZ property without making either of those mistakes. It covers the materials that work in our climate, the clearances the manufacturers actually require, the size and finish options available, and how to fit the cover so the unit keeps running at full efficiency.

The fast answer: For most NZ homes, a powder coated aluminium louvre cover with 100mm minimum clearance on all serviceable sides is the right pick. Aluminium does not rust, the louvres pass enough air to keep the unit happy, and the finish lasts 15 to 25 years depending on how close to the coast you are. Browse the SD Aluminium heat pump cover range or talk to the team for a custom size.

Why bother with a cover at all

Three reasons come up over and over with NZ homeowners.

Looks. The outdoor unit is usually mounted in the most visible part of the side wall, between the driveway and the bedroom window. A cover turns it into a quiet design feature instead of a beige plastic box. On modern homes with horizontal cladding, a horizontal louvre cover lines up with the cladding lines and disappears into the facade.

Weather and salt. NZ has more coastline per capita than almost anywhere else. Salt fog drifts inland for several kilometres, and the fan grille on a heat pump is one of the first surfaces to corrode. A louvred cover does not stop salt entirely, but it cuts the direct exposure, reduces UV damage on the plastic top, and stops leaves and pine needles from packing into the coil. Owners on coastal Auckland, Wellington and Christchurch sites tend to see this benefit most clearly after the first winter.

Sound. A heat pump in defrost mode produces a low frequency hum that bounces off hard walls. A correctly sized aluminium cover with louvred sides absorbs and redirects some of that sound away from the closest window. It is not a noise cancelling product, and a cover will not fix a unit installed in a tight corner, but a typical louvred cover on an open wall reduces perceived hum by a few decibels in the closest room.

What a heat pump cover is not

A cover is not a tarp. It is not a box. It is not an enclosure that wraps the unit on all five sides. Any of those will trap heat, block airflow, and force the unit into short cycling, which raises power bills and shortens compressor life. Manufacturers including Mitsubishi, Daikin, Panasonic and Fujitsu all publish minimum service clearances, and any cover that fits the unit has to respect those distances.

A useful way to think about it: the cover is a three sided louvred shroud with an open back against the wall, an open base and open louvred sides. Air still passes freely through the louvres, the fan still discharges through the front, and the cover only hides the look of the unit. A good NZ installer will hand you the manufacturer service sheet on request and confirm the cover does not breach any clearance on it.

Materials: aluminium, timber, plastic, steel

Four materials show up regularly on NZ heat pump covers. They are not all equally good outdoors.

Material	Lifespan in NZ	Maintenance	Suitable use
Powder coated aluminium	15 to 25 years	Rinse once or twice a year	Coastal, inland, residential and commercial
Treated timber (cedar, vitex)	8 to 15 years	Oil annually, replace blades as needed	Inland sheltered residential
Galvanised or stainless steel	10 to 20 years	Spot rust touch ups	Commercial or industrial settings
Plastic or polypropylene	5 to 10 years	None practical, replace when faded	Budget residential, sheltered sites

Aluminium is the default for NZ residential because it does not rust, the powder coat lasts decades, and the material is light enough to be wall mounted on existing brackets. A typical aluminium cover frame is built from aluminium equal angle and U channel, with the louvre blades sitting in the angle slots. The whole frame can be flat packed and screw assembled on site.

Timber looks warm and fits well on weatherboard homes, but it asks for ongoing maintenance. Cedar blades hold up better than pine, but even cedar greys off and needs oiling every 12 to 18 months. On the coast, timber covers are usually re bladed within ten years.

Steel covers, usually galvanised square hollow with weld mesh sides, show up on commercial installs where the unit is exposed to vehicle impact or vandalism. Steel rusts faster than aluminium, so for a residential site the look is heavier and the upkeep is more.

Plastic covers are the cheapest option at retail and look fine in year one. By year three on a coastal NZ site, UV damage has chalked the surface, and the panel ties have usually failed. They are a stopgap rather than a long term solution.

Sizing the cover: clearances that actually matter

This is the part that most online product listings glide over, and the part where most home owner DIY covers fail. Every heat pump manufacturer publishes minimum service clearances. They differ a little by model, but the typical residential split system needs at least these distances around the outdoor unit:

• Front of the unit (fan discharge side): 500mm minimum, more is better. The louvre cover front blades need to sit 100mm or more clear of the fan grille, with the cover itself opening forward so air can leave the louvres without hitting another vertical surface.
• Sides (left and right): 100mm minimum between the unit side and the cover side panel. This keeps the heat exchanger airflow from being choked.
• Top: 300mm minimum between the unit top and the cover top, for both servicing and air recirculation.
• Back: 50mm minimum between the unit back and the wall. If the unit is already mounted to brackets this is usually fine, and the cover does not need to wrap the back at all.
• Bottom: The cover should not sit on the unit base. Mount the cover to the wall, not to the unit.

Measure the outdoor unit first, then add the clearances above, then add 20mm to each external dimension for finger clearance and fixing tolerance. That gives the cover external size.

As a working example, a typical 5kW split system outdoor unit is around 800mm wide by 320mm deep by 600mm tall. A correctly sized cover for that unit is around 1000mm wide by 500mm deep by 800mm tall, mounted with the back open against the wall. Smaller covers exist for compact 2.5kW units, and larger covers are needed for ducted systems and twin head outdoor units.

Off the shelf or custom

SD Aluminium ships covers in two main paths.

The standard residential cover uses preset internal dimensions sized for the most common heat pump models on the NZ market. The frame is powder coated aluminium, with square louvre blades, and ships flat packed for site assembly. This option suits most single head outdoor units on residential properties and is the fastest to install.

A custom cover is sized to the exact outdoor unit and mounting situation, priced per square metre of louvre face area. This is the right path when the unit is non standard, when twin or triple outdoor units sit side by side, when the cover needs to match a specific cladding colour, or when the install is on a parapet roof or balcony where the clearances are tight. Custom covers can use square louvre blades, fusiform shaped blades, or U channel paling depending on the look you want.

If you are not sure which path fits, send the unit model number, the wall photo and the available space dimensions. The team prices both options and explains the trade off.

Finishes and colour matching

Powder coated aluminium can be finished in any RAL or Resene colour. The most common NZ choices are:

• Matt black: default modern look, lines up with black window joinery and dark cladding.
• Charcoal or Karaka: works against Coloursteel Karaka or grey weatherboard.
• Off white or Lignite: blends into white plaster or Linea cladding.
• Wood grain transfer: a vinyl wrap on aluminium for a timber look without the timber maintenance.

If you are matching to an existing window joinery powder coat, give the team the powder coat code (or a sample) before the order so the cover and joinery cure to the same finish.

Installation

A standard residential cover installs in 30 to 60 minutes once the unit is in place. The general steps are:

1. Check the unit clearances first. Confirm the cover external size leaves the manufacturer minimums on all sides.
2. Mount the wall brackets. The cover is wall hung, not unit hung. Drill two or four masonry anchors into the cladding studs or block work behind the unit, sized for the cover weight.
3. Assemble the frame. The aluminium angle frame screw assembles into a three sided shroud, with the louvre blades fitted into the slots before the front face goes on.
4. Hang the cover. Lift the assembled frame onto the wall brackets, level it, and lock it down with the security screws supplied.
5. Test the unit. Run the heat pump through a heat cycle and a cool cycle. Listen for fan strain, watch the airflow at the cover front, and check the unit is not short cycling. If it is, the front clearance is too tight and the cover needs to come forward.

If the heat pump is still under warranty, take a photo of the install showing the clearances and keep it with the installation receipt. Some installers will void cover related warranty claims if the cover has been retrofitted poorly, and the photo is the simplest way to prove the install was done by the book.

Maintenance

Powder coated aluminium covers ask very little. For most NZ inland sites, one rinse a year with clean water removes pollen, dust and light salt. For coastal sites within 500m of the sea, a rinse every six months keeps the salt build up from sitting on the powder coat for too long. A soft sponge and warm water clean off anything stubborn, and harsh solvents are not needed and not recommended.

Check the cover fixings once a year, retighten anything that has worked loose, and confirm the cover has not shifted into the unit clearances. If a louvre blade is dented from a stray ball or a falling tool, it can usually be swapped at the blade level rather than replacing the whole cover.

NZ climate considerations

Three NZ specific points often shape the cover spec.

Coast and salt. Within 500m of the sea, specify the powder coat at marine grade, and confirm the fixings are stainless rather than plain zinc plated. Aluminium itself is fine, the failure point on the coast is usually the screws.

UV. NZ sits under a thin ozone layer for half the year, which ages plastic and timber faster than the same product would age in Europe or the northern hemisphere US. Aluminium is unaffected by UV beyond the cosmetic coat. If you are comparing a $300 plastic cover to a $700 aluminium one, the UV alone usually closes that gap inside five years.

Servicing access. The cover should hinge open or lift off without tools so the heat pump tech can service the unit annually. Fixed welded covers fail this test, and the homeowner ends up either skipping service visits or paying for an extra hour on each visit. Confirm the cover model supports tool free access before you order.

What it costs in NZ (May 2026)

Indicative pricing on the NZ market in mid 2026, for a single head residential outdoor unit cover:

Cover type	Material	Typical NZ retail
Standard size aluminium louvre cover	Powder coated aluminium	$450 to $700
Custom sized aluminium louvre cover	Powder coated aluminium, made to measure	$650 to $1,200
Treated timber cover	Cedar or vitex	$400 to $900
Steel weld mesh enclosure	Galvanised or powder coated steel	$500 to $1,400
Plastic clip on cover	UV stabilised polypropylene	$150 to $300

Installation runs $150 to $350 on top, depending on cladding type and access. For comparison, a heat pump compressor replacement on a 5 to 7kW residential unit runs $1,800 to $3,000 plus labour, which is why the cover is usually thought of as cheap insurance rather than a discretionary upgrade.

Frequently asked questions

Will a heat pump cover void my warranty?

Not if it respects the manufacturer service clearances. A correctly sized louvred cover that leaves the published front, side and top clearances is supported by every major brand sold in NZ. A wrapped enclosure that chokes airflow can void the warranty, which is why measuring the clearances first matters more than picking the look.

Can I use a heat pump cover indoors?

This guide is about outdoor unit covers. Indoor head units are wall mounted and do not need a cover. If the look of the indoor head bothers you, talk to your installer about a ducted or concealed system at the next renovation rather than wrapping the indoor head.

Do I need a cover if my unit is already under the eaves?

If the eaves overhang the unit by 600mm or more and the site is not coastal, a cover is a nice to have rather than essential. The eaves block most of the rain and UV. On a coastal site, salt still drifts in horizontally, and a louvre cover still earns its keep.

Can the cover sit on the same wall as a window?

Yes, with two caveats. First, the fan discharge needs to point away from the window so warm or cold air is not blown directly across it. Second, the cover sound benefit is bigger when the window is to the side of the unit rather than directly in front.

How heavy is an aluminium heat pump cover?

A standard residential aluminium cover with louvre blades weighs around 8 to 14kg assembled. It is light enough for one person to hang on the wall brackets once the frame is built up. Steel covers in comparable sizes run 20 to 35kg and usually need two people to fit.

Can the cover be moved if we shift house?

Yes. Because the cover is wall hung on brackets rather than fixed to the unit, it lifts off in a minute. The brackets stay on the old wall and a fresh set goes on the new wall, sized to the new unit. The cover itself is reusable as long as the new unit is within the original size envelope.

What about heat pump cages for security?

Cages are a different product, usually a galvanised steel weld mesh frame with a padlock, fitted on commercial or rental properties to prevent theft of the copper coil. A residential louvre cover is not a security cage. If theft is a concern, the cage and the louvre cover can be combined, with the cage on the inside and the louvre cover on the outside.

For sizing help, custom colour matching or a quote on a specific outdoor unit, send the unit model and a wall photo to the SD Aluminium team. The heat pump cover system sits inside the broader aluminium louvre range, which also covers square louvre blades and fusiform blades for screens, fences and pergolas. If you are also looking at aluminium materials more broadly, the aluminium sheet grades guide covers the alloys that pair well with a louvre system.