Most heat pump outdoor units don’t need a cover. They’re built to sit outside through rain, wind and frost, and they handle all three better than most people expect. When someone asks about a cover, it’s usually for one of two reasons: they don’t like looking at a white box beside the deck, or they’re worried about the weather. Both are fair enough. But the wrong cover can do more harm than a decade of southerlies. One rule sits above everything else: the outdoor unit has to breathe.
Why your heat pump needs airflow more than shelter
In heating mode, the outdoor unit pulls in outside air, takes heat out of it, and blows the cooled air back out. For that to work it needs clear space. Block the intake, or trap the cold discharge air so the unit sucks it straight back in, and three things follow:
- the room heats more slowly and never gets as warm
- the coil ices up faster and the unit defrosts more often
- the compressor works harder for the same warmth, so you pay more for less.
A unit pulling its own discharge air back in is one of the listed causes of frequent defrosting. So is airflow blocked by plants and shrubs. Box the unit in and you’ve created the exact problem you were trying to prevent.
→ Related: Heat pump problems and what causes them
What a heat pump cover is actually for
If the unit spoils your deck or the front path, a cover is a reasonable call, as long as it’s made for a heat pump. A properly built one:
- keeps the clearances the manufacturer specifies on every side
- has open louvres or slats at the front so the discharge air gets away
- lifts off or opens up so a technician can reach the unit
- uses materials that won’t rust onto it, such as powder-coated aluminium with stainless fixings.
Talk to your installer before you buy. Some brands work with approved cover makers who design to their clearance and airflow rules, and an installer can check whether a louvred screen suits your model and the spot it sits in. If you’re buying a new heat pump, raise the cover at quote stage so the unit goes somewhere it can be screened properly.
→ Related: How to choose a heat pump and an installer
Do you need a cover for frost and snow?
Frost on a cold morning is normal, and the unit clears it itself in its defrost cycle. A cover won’t stop frost forming, because the coil runs colder than the outside air while the unit is working. Our guide on heat pump problems covers what normal defrosting looks like and when it points to something else.
Snow is a different story in Central Otago, the Mackenzie Basin and the high country around Queenstown. The risk there is snow piling up against the unit and blocking the coil or the fan. The fix is height and drainage, not a wrap:
- Get it off the ground. Outdoor units should sit on a secure base or wall brackets rather than straight on the ground. In snowy spots, ask your installer to set it high enough to clear the snow that usually settles there.
- Let it drain. In heating mode the unit makes water as it defrosts. Mount it so water drains away freely, not onto a path or step where it can freeze.
- Keep it clear. If snow drifts against the unit, switch it off and brush the snow away by hand. Don’t chip at ice on the coil. Let the defrost cycle deal with it.
→ Related: Heat pump winter settings for cold snaps
Do you need a heat pump cover near the sea or in Rotorua?
On the coast the real threat isn’t rain, it’s corrosion. Salt air off the sea, and sulphur gases in geothermal areas like Rotorua and Taupō, slowly eat into metal. New Zealand has corrosion maps that rate areas from low (C1) to very high (C5) risk, and your installer can tell you which zone you’re in.
A cover doesn’t keep salt out, because salt travels in the air the unit has to breathe. What does help:
- Ask about extra corrosion protection when you buy, such as a factory or aftermarket coating on the coil. In higher-risk zones it may be recommended.
- Wash the outdoor unit regularly. A gentle wash every six months with car wash liquid, then a rinse with the hose, lifts salt and grime off. Don’t use dishwashing liquid.
- Book regular services. A technician can clean the coils and the drain tray, where salt and dust build up.
- Remember the indoor unit. Salty air comes in through open doors and windows, so it reaches the indoor unit too.
→ Related: Heat pump servicing and what a technician checks
Should you shade a heat pump from sun, wind and leaves?
A well-ventilated spot out of direct sun suits the outdoor unit best. If you add shade, keep it well above the unit and open at the sides so air still moves freely. Where the unit sits also has to fit council rules, your bedrooms and your neighbours, so talk it through with your installer. Our guide on heat pump boundary rules covers the council side.
What not to cover a heat pump with
- Never wrap it in a tarp or plastic sheet, even with the unit switched off. Trapped moisture speeds up rust, and it’s easy to forget the cover is there when you turn the unit back on.
- Don’t stack things on top or lean things against it. Outdoor furniture, pot plants and firewood all block airflow.
- Don’t let plants grow over it. Trim hedges and climbers back so there’s clear space all round.
- Don’t box it in with a solid front, even if there are gaps at the sides.
Who can check your outdoor unit?
If you’re not sure your unit is placed or covered well, a servicing visit is the moment to ask. Find a heat pump servicer near you, or pick your town and filter by the job.