Heat pumps don’t come with a use-by date. Some run happily for many years. Others wear out early on a salty Raglan section or in a steamy Rotorua backyard. The question isn’t how old yours is. It’s whether it still heats the room properly, how much it’s costing you in repairs, and what’s sensible to do with the old one.
How do you know when a heat pump needs replacing?
No brand can give you a fixed lifespan, because so much depends on the site and how the unit was looked after. The things that shorten a heat pump’s life are well known:
- dust, dirt and salt air
- weather extremes and an unreliable power supply
- poor installation, or the wrong unit for the space
- how often it’s maintained, and how well
- heavy on/off cycling, frequent defrosting and constant mode changes.
With that in mind, these are the signs worth taking seriously:
- It can’t keep the room warm on cold mornings, even after a service and clean filters.
- It defrosts again and again and never quite catches up. Constant failed defrosts can mean the unit is too small for the room, short of refrigerant or due for repair.
- Repairs keep coming back, especially refrigerant leaks.
- Rust and corrosion on the outdoor unit or coils. Coastal salt and geothermal sulphur both eat away at metal, and indoor units suffer too where outside air gets in.
- It’s old and noisy. Many heat pumps over about ten years old run on R22 or R410A refrigerant. Newer units mostly use R32, which has a lower global warming potential, and quiet operation has improved a lot over the last decade.
→ Related: Common heat pump problems and what causes them
Is it better to repair a heat pump or replace it?
Start with the paperwork. If the unit is still under warranty, call the installer or the brand before anyone else touches it, because the warranty can depend on who does the work. General Airstage, for example, offers a five or six year parts and labour warranty, depending on whether the installer is accredited.
Out of warranty, get a proper diagnosis from a technician and ask them to put it in writing: what’s wrong, what the fix involves, and whether they’d expect other parts to fail soon. Then weigh it up:
- Repair when the fault is a one-off (a fan motor, a sensor, a circuit board) and the unit otherwise heats well.
- Replace when the same fault keeps returning, when the refrigerant keeps leaking, when corrosion is spreading through the coil, or when the unit never really heated the room in the first place.
If the old unit was undersized, don’t simply swap like for like. Work out what the room actually needs. Our guide on what size heat pump you need explains how.
→ Related: When to replace a heat pump and what the swap involves
Can you reuse the old pipes, ducts and brackets?
Often, yes, and it can save time and mess.
Can the refrigerant pipes stay?
Replacing a heat pump used to mean ripping out all the copper pipe as well, because of the mineral oil left behind by older refrigerants. Some brands now have pipe reuse methods that clean out that old oil so the existing pipes can stay, with only the indoor and outdoor units swapped. Mitsubishi Electric’s version also works on systems first installed by other brands. Whether your pipes can be reused depends on their condition, size and route, so ask your installer to check, and to say so in the quote.
What about the ducting?
On a ducted system, the old ducts can stay if they’re in good condition and suit both the new unit and the rooms they serve. Your installer needs to confirm that for your house.
Can the new outdoor unit sit on the old brackets?
It should sit on a secure base or brackets, not straight on the ground, to cut vibration and rust. In heating mode it also needs to drain freely. A new unit may be a different size or weight from the old one, so don’t assume the old brackets will do. Check they’re sound and rated for the new unit, and replace the rusty ones while the unit is off.
→ Related: Ducted vs high wall heat pumps: which suits your house?
What happens to the old refrigerant gas?
This is the part you can’t skip. Under the Ozone Layer Protection Act 1996, it’s an offence to knowingly release a controlled refrigerant into the air while dismantling air-conditioning equipment. The only allowance is a small, unavoidable release while hoses are being connected or disconnected. So the old unit’s gas has to be pumped out and recovered by a trained technician before anything is unbolted.
Recovered refrigerant is collected by Cool-Safe, a charitable trust that destroys old synthetic refrigerants. Since March 2026 that happens at a national destruction facility in Kawerau. From 1 April 2027, a regulated scheme means anyone selling, handling or disposing of synthetic refrigerants must register, meet compliance standards and report what they recover. Further competency requirements for technicians follow from 2030.
What that means for you:
- Ask how the old gas will be handled before you accept a quote. A good answer names who recovers it and where it goes.
- Choose a trained technician. Cool-Safe keeps a list of recognised technicians, who have done WorkSafe training as fillers or refrigerant technicians.
- Don’t let anyone cut the pipes on an old unit that still holds gas.
→ Related: Who can install or decommission a heat pump
Can you get a grant for a replacement heat pump?
The Warmer Kiwi Homes grant is for homes without a working fixed heater in the living area, so a working heat pump usually rules you out. Our guide on heat pump grants in NZ has the full eligibility rules.
→ Related: The Healthy Homes heating standard explained
Find an installer to replace your heat pump
A replacement is a repair, a removal and a new install in one visit, so pick an installer who does all three. Find a heat pump repairer near you, or choose your town and filter by the job.