Buying your own heat pump: does it actually save money?

Every winter we take calls from Waikato homeowners who bought a heat pump from a big-box retailer or an online deal site and now need someone to install it. Sometimes it works out fine. Often it doesn't - and the problems were never visible at checkout. This is the honest picture of buying your own unit versus supply-and-install, from an installer who quotes both.

1. Why the online deal looks so good

A heat pump for $999 next to an installed quote of $3,200 looks like a $2,200 saving. It isn't - it's a component price next to a finished-job price. The online listing is the box on a pallet. The installed quote is the box, the copper pipework, the electrical work, the mounting, the vacuum test, the refrigerant commissioning, the sizing assessment, and the warranty backing behind all of it.

The comparison is also rarely like-for-like on the unit itself. The headline deals are usually budget import brands or runout stock in whatever capacity happens to be cheap that week - not the specific model and kW rating your room actually needs.

And here is the part most buyers never see: installers don't pay retail for units. We buy at trade pricing, which is why a genuine NZ-stock unit inside a supply-and-install quote costs far less than its ticketed retail price. A chunk of the saving you think you're making online is a saving the installer would have passed on anyway.

2. The warranty split problem

This is the single biggest reason we're cautious about the buy-your-own route. When you buy the unit from one company and the installation from another, you've split responsibility for the system down the middle. While everything works, nobody notices. The day something fails, it matters enormously.

Here is how it plays out. The unit stops heating in July. You call the retailer, who says the fault is likely with the installation and refers you back to your installer. The installer checks their pipework and electrical, confirms their workmanship is sound, and points back at the unit. The installer can only warranty what they did - the workmanship - because they didn't supply the hardware. You're now the project manager of a dispute between two companies, in the middle of winter, with a dead heat pump on the wall.

It gets worse if the paperwork isn't right. Manufacturer warranties require installation by a suitably qualified installer to be valid - it's in the terms of every major brand sold in NZ. If the unit was fitted by an unqualified mate-of-a-mate, or it's a parallel import with no NZ warranty coverage at all, the manufacturer can decline the claim outright.

With supply-and-install, none of that triangle exists. One company supplied the unit, sized it, installed it, and commissioned it. If anything goes wrong, you make one phone call and it's our problem to sort - unit, install, or anything in between.

3. Sizing: the mistake you can't undo

When you buy online, you're guessing the capacity. Room size, ceiling height, insulation, window area, orientation, and the Waikato's frosty winter mornings all feed into the kW a room actually needs - and none of them are visible from a product listing. Our heat pump sizing guide walks through the full calculation if you want to see what goes into it.

• Undersized:the unit runs flat out all winter, chews through power at its least efficient operating point, and still doesn't get the room warm on a frosty morning. This is the most common outcome of buying on price
• Oversized: the unit short-cycles - blasting the room warm, shutting off, then restarting over and over. That means uneven temperatures, poor dehumidification, more wear on the compressor, and higher running costs than a correctly sized unit

Both mistakes are permanent. Once the unit is mounted, piped, and commissioned, you can't return it - no retailer takes back an installed heat pump. The sizing decision is locked in at the moment you pay, which is exactly why a site assessment belongs before the purchase, not after.

4. Parts and service reality for budget imports

The deal sites are full of brands you've never heard of. Some of those units run without complaint for years. The problem isn't the day you buy one - it's year four, when the fan motor or control board gives out.

Major brands hold spare parts in New Zealand and run service networks with trained technicians across the Waikato. Budget import brands usually have neither. When a part fails, a licensed technician can diagnose the fault but can't source the component - there's no NZ parts stock, no distributor support line, and often no wiring documentation. The repair that should cost $300 becomes impossible at any price.

At that point the unit is disposable. You're paying for removal, disposal, a new unit, and a second installation - everything you paid the first time, plus the teardown. One failed component on a no-name brand can cost more than the entire price gap between the budget unit and a quality one.

5. The real cost math

Here is what the two routes actually cost for a typical high-wall unit in the Waikato in 2026, once every line item is on the table.

Once everything is counted, the totals typically land within a few hundred dollars of each other - except one column buys a budget import sized by guesswork with a warranty split two ways, and the other buys a quality unit from a brand with NZ parts supply, sized for your actual room, with one company standing behind the whole job. Because we buy at trade pricing - and as an authorised Mitsubishi Electric installer - the unit in our quote is a better unit than the one in the online cart, at a smaller markup than you'd expect.

6. When buying your own unit does make sense

We'd be lying if we said BYO never works. It can - under specific conditions, all of which need to be true at once.

• It's a genuine NZ-stock, major-brand unit at a legitimate clearance price:model runouts and end-of-season clearances on brands with NZ warranty and parts support are real bargains. A mystery brand at a permanent "sale" price is not
• Your installer confirmed the size BEFORE you bought: a quick call or site visit to confirm the kW rating suits your room turns the biggest gamble in the whole exercise into a known quantity
• You had an installer agreed beforehand: price the installation before you pay for the unit, not after it's sitting in your garage. Supply-only install rates vary, and some installers won't touch certain brands at all

If all three line up, you can genuinely come out ahead. If any one is missing, the odds tilt quickly the other way.

7. How Airmax handles customer-supplied units

We do install customer-supplied units, and we quote them case-by-case. Before we price the job we'll ask what the unit is, where it came from, and what room it's going into - because the answers change whether the install is a good idea at all.

• Case-by-case quotes:a genuine NZ-stock unit from a major brand, correctly sized, is a straightforward job. An unfamiliar import or a unit that's wrong for the room gets priced - and advised on - differently
• Workmanship warranty only:we stand behind our installation work without reservation, but we can't warranty hardware we didn't supply. The unit itself stays between you, the retailer, and the manufacturer
• Straight answers upfront:if a unit isn't worth installing - wrong size, no NZ parts support, or a brand we know causes grief - we'll tell you before any money changes hands, not after it's on the wall

8. The bottom line

The online sticker price is real, but it's the price of a box, not a working heating system. By the time you add a supply-only installation, the electrical extras, and the risk you're carrying on sizing, warranty, and parts, the saving usually shrinks to a few hundred dollars - and sometimes disappears entirely.

For a few hundred dollars, supply-and-install buys you a better unit, the correct size for your room, a valid manufacturer warranty, a workmanship warranty, and one team accountable for all of it for the next decade. That's not an upsell - it's just what the math says once every line is on the page.

And if you've already found a deal you think is genuinely good - send it to us before you buy. We'll tell you straight whether it's the right unit for your room and what the install would cost, so you can make the call with the full picture in front of you.