In most cases, you should not cover your outdoor heat pump unit during a storm — even temporarily. Modern outdoor units are designed and built to withstand rain, wind, and New Zealand's varied weather conditions. Covering the unit incorrectly can restrict airflow, cause the system to overheat or malfunction, and may even void your warranty. Here's what you need to know to keep your heat pump safe.
Why Outdoor Units Are Built for Bad Weather
Your outdoor unit — sometimes called the condenser or compressor unit — is specifically engineered to operate in outdoor conditions. Manufacturers design these units to handle heavy rain, strong winds, and even light hail. The casing is weatherproof, and the internal components are protected from moisture ingress under normal storm conditions.
In New Zealand, heat pumps must comply with the NZ Building Code and relevant installation standards, and reputable installers will position units to minimise exposure to the worst weather. If your unit was installed by a qualified professional, it should already be in a reasonably sheltered location.
The Real Risks of Covering Your Unit
Covering an outdoor heat pump unit — even with a tarpaulin or purpose-made cover — poses several genuine risks:
- Restricted airflow: Heat pumps need to draw in and expel large volumes of air. Blocking the fan or vents, even partially, can cause the unit to overheat or trigger a fault code.
- Moisture trapping: A cover can trap condensation and humidity against the unit, accelerating corrosion — the opposite of what you intend.
- Debris accumulation: Covers can catch leaves, twigs, and other storm debris, pressing them against the unit rather than letting them blow clear.
- Operating while covered: If the heat pump runs while covered (which can happen automatically), it can cause serious mechanical damage within minutes.
- Warranty issues: Many manufacturers specify that covers should not be used while the unit is operational, and some void warranties if damage results from improper covering.
What You Should Do Before a Storm
Rather than reaching for a tarp, take these practical steps before severe weather hits:
- Turn the unit off at the controller or isolating switch if you're concerned about an extreme storm. This removes the risk of it running while obstructed.
- Clear the area around the unit of loose objects — garden furniture, pots, or anything that could become a projectile and strike the unit.
- Check the clearances — ensure nothing has grown or been placed too close to the unit that could restrict airflow or fall onto it.
- Inspect the mounting — confirm the unit is still securely fixed to its bracket or pad. If it looks loose, contact a heat pump technician before the storm arrives.
- Note your model and installer details in case you need to make a warranty or insurance claim after the storm.
After the Storm: What to Check
Once the weather has passed, do a visual inspection before restarting the unit:
- Look for visible damage to the casing, fan grille, or refrigerant lines.
- Check that no debris (leaves, branches, hail) has lodged inside the grille or around the base.
- Ensure the unit is still level and securely mounted.
- Look for any bent fins on the coil — these can restrict airflow and reduce efficiency.
- If everything looks fine, restart the unit and listen for any unusual noises.
If you notice bent fins, damaged refrigerant lines, or the unit is making strange sounds, do not continue operating it. Switch it off and call a qualified heat pump technician.
What About Hail?
Hail is a legitimate concern in some parts of New Zealand, particularly in Canterbury and parts of the South Island. Severe hailstorms can dent the aluminium fins on the outdoor coil, reducing efficiency. Some homeowners in high-hail areas install permanent hail guards — metal mesh or louvred screens fitted by a professional that protect the coil without restricting airflow. This is a much safer option than an improvised cover and is worth discussing with your installer if hail is a regular issue in your area.
Coastal and High-Wind Locations
If your home is in a coastal area or an exposed, high-wind location, speak to your installer about appropriate siting and mounting. BRANZ provides guidance on building in exposed NZ environments, and your heat pump installer should be familiar with the requirements for your specific climate zone. Salt-air environments may also require a unit with a corrosion-resistant coating — check with your manufacturer or installer.
For general energy efficiency and heat pump guidance, Energywise is a useful NZ government resource.
When to Call a Professional
Contact a qualified heat pump installer or technician if:
- The unit has been physically struck by debris or a falling object.
- You can see damage to the refrigerant lines (look for oily residue or frost in unusual places).
- The unit won't restart after the storm, or displays a fault code you can't clear.
- The fan grille is bent or the fan blade appears damaged.
- You're unsure whether the unit is safe to operate.
Refrigerant handling is restricted work in New Zealand and must only be carried out by a registered refrigeration and air conditioning technician. Never attempt to repair refrigerant lines yourself. You can find qualified local heat pump installers and technicians on tradedirectory.co.nz.
For peace of mind, it's also worth checking that your home and contents insurance covers storm damage to heat pump units — policies vary, so confirm the details with your insurer.
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