Heat Pump Service 2026: What to Expect & When

How often does a heat pump need servicing?

Once a year. That's the standard interval for air source and ground source systems, and it's non-negotiable if you want to keep the manufacturer's warranty intact.

Most warranties, Vaillant, Mitsubishi, Daikin, Samsung, all of them, state in the small print that annual servicing by a qualified engineer is a condition of cover. Miss a year and you've got a warranty claim that the manufacturer can refuse. We've seen this happen. A homeowner in Leeds skipped two services, had a compressor fail in year four, and ended up with a £3,800 repair bill the manufacturer wouldn't touch.

Some newer models with longer warranties (12 years in the case of some Vaillant arotherm plus units) are even stricter. One missed service and the long warranty collapses back to the statutory minimum.

But here's the honest bit. A heat pump is a sealed, low-maintenance piece of kit compared to a gas boiler. Nothing combusts. There's no flue to check, no gas to leak. The parts that wear out, fans, pumps, the compressor, don't usually fail inside year one or two. So the annual service is partly about catching early problems and partly about ticking the warranty box.

Twice-yearly servicing isn't necessary for domestic systems. Some commercial installers push it. Ignore them unless you've got a complex multi-zone setup with buffer tanks and weather compensation that genuinely needs more attention.

What does a heat pump service actually cover?

A proper service takes 60 to 90 minutes and covers refrigerant pressure, electrical connections, the heat exchanger, and overall system performance.

Here's what should happen on a typical air source visit:

• Refrigerant pressure check. The engineer connects gauges to the service ports and reads the high and low side pressures. Low pressure means a leak somewhere. On systems above 3kg of refrigerant, F-gas regulations require a formal leak check every 12 months anyway.
• Heat exchanger clean. The outdoor unit's coil picks up leaves, pollen, dust, and in coastal areas, salt. A clogged coil cuts efficiency hard. The engineer should hose it down or use a specialist coil cleaner.
• Fan and motor inspection. Bearings, blade condition, mounting bolts. Loose fans vibrate and get noisier over time, which is a common complaint on units installed close to bedrooms.
• Electrical check. Terminal connections tighten up or loosen with thermal cycling. The engineer should torque-check them and look for signs of arcing or discolouration.
• Condensate drain. The outdoor unit produces condensate in heating mode. A blocked drain causes ice build-up in winter, which the heat pump will try to defrost repeatedly and burn electricity doing it.
• System performance. Flow and return temperatures, flow rate, and ideally a calculation of the current COP against design conditions.

Ground source systems get the same treatment plus a ground loop pressure check and a glycol concentration test. If your antifreeze concentration drops below spec, the loop can freeze in a hard winter and that's a very expensive problem.

What shouldn't be on the invoice? A pointless "system flush" if your installer did a proper magnetic filter install and inhibitor dose at commissioning. Some engineers try to add this as a £200 upsell. Push back and ask what they found in the filter.

What to ask your engineer before and after the visit

Ask for the service report in writing, the measured flow and return temperatures, and the refrigerant pressure readings. You need these on paper.

Before they arrive, send them your installation manual or at least the make and model. A good engineer will have serviced your model before. A bad one will arrive, Google it on their phone, and improvise.

Ask upfront: are you F-gas certified? For any work involving the refrigerant circuit, this is a legal requirement. If they can't produce their certificate, don't let them touch the sealed system.

After the visit, you want three things on the paperwork:

1. The actual measurements. Not "system operating correctly" but the real numbers. Flow temp 45°C, return 40°C, refrigerant pressures X and Y bar.
2. A note on anything that's borderline. Is a part showing wear? Is the inhibitor level getting low? You want to know about it now, not when it fails.
3. Confirmation the service meets your warranty conditions. Some manufacturers have a service checklist you can download. Hand it to the engineer and ask them to sign it off.

One specific thing to check post-service: the system should run quietly. If the outdoor unit is noticeably noisier than before, something's wrong with the fan mounting or balance. We've covered heat pump noise levels in detail elsewhere, worth a look if you've got concerns.

And honestly, this one depends on your installer and your relationship with them. Some firms do a cracking job and genuinely care. Others treat the annual service as a tick-box exercise and are out the door in 25 minutes. If the second one is yours, find someone else next year.

How servicing affects your warranty and grant conditions

Miss an annual service and most manufacturers can void your warranty entirely. If you took the Boiler Upgrade Scheme grant, you also agreed to keep the system operational for at least a year.

The BUS commitment is a specific legal condition of the £7,500 (or £9,000 for oil replacements off the gas grid) grant. If you rip the heat pump out within the first 12 months and go back to a gas boiler, Ofgem can claw back the money. Annual servicing is how you demonstrate you're actually using and maintaining the system. Keep the paperwork.

The warranty issue is bigger money long-term. A heat pump compressor replacement runs £2,000 to £4,000 depending on model. The warranty is the only thing standing between you and that bill in years 3 through 10.

Here's what most guides won't tell you. Manufacturers can and do audit warranty claims. They'll ask for service records before authorising a repair. If you've got a gap, even one missed year, they can refuse. Keep every invoice and every service report in one folder, physical or digital.

If you're still deciding on install, our heat pump grant guide covers the BUS and ECO4 routes in detail. Both have ongoing conditions worth understanding before you sign.

Routine servicing versus a repair call-out: knowing the difference

Routine servicing is scheduled, preventive, and typically £150 to £300. A repair call-out is reactive, usually £80 to £150 for the visit plus parts, and happens when something's actually gone wrong.

Don't conflate the two. If your pump is making a new noise, cycling constantly, or the house won't get warm, that's a repair, not a service. Phoning your installer and asking for "the service" when there's a fault wastes a slot and often means they turn up without the right parts.

Signs you need a repair, not a service:

• The pump keeps tripping the RCD
• You're hearing gurgling in the pipes (air in the system)
• Flow temperatures are stuck high but the house is cold (likely a flow issue, not refrigerant)
• The outdoor unit has visible ice that isn't clearing after a defrost cycle
• Your bills have jumped sharply with no change in weather or usage

We see one specific issue a lot in year two or three: homeowners booking a service when the real problem is a weather compensation curve set wrong at commissioning. The engineer services the hardware, finds nothing, charges £180, and the house is still cold. The fix is a software setting, not a mechanical one. If you're uncertain, describe the symptoms when you book and ask whether a service or a diagnostic visit is more appropriate.

One tangent worth mentioning. If you've got solar panels and a heat pump, the two systems interact in ways that affect running cost calculations more than they affect servicing. But that's a separate issue, we've covered it in our Smart Export Guarantee guide.

How to find a qualified heat pump service engineer

Use an MCS-certified installer, ideally the firm that installed your system. For refrigerant work, insist on F-gas certification.

The easiest route is going back to whoever installed the pump. They know the system, they've got the commissioning data, and they're often cheaper for existing customers. Many offer annual service plans at £180 to £220 fixed.

If the original installer has gone bust, moved on, or just gives you bad service, use the MCS installer database and filter by heat pump service. Not every MCS installer services pumps they didn't fit, some will only service their own installs, so phone ahead.

For Mitsubishi Ecodan, Vaillant arotherm, Daikin Altherma and Samsung EHS systems specifically, the manufacturers run accredited service networks. Vaillant's Advance network and Daikin's D1 installers tend to know these systems inside out. Pay the small premium for brand-trained engineers if your pump is still inside its long warranty.

What to ask when you phone round:

1. Are you MCS certified and F-gas qualified?
2. Do you service [your make and model] regularly?
3. What's included in the service and how long does it take?
4. Do you provide a written report with measurements?
5. What's the all-in cost including VAT?

If anyone quotes under £120, be suspicious. A proper service takes over an hour of a qualified engineer's time plus their van costs and insurance. Below that, something's being skipped.

And if you're not yet installed but researching, our heat pump quote guide covers what to look for in a good installer, servicing commitments are one of the biggest tells of whether a firm is in it for the long haul or just chasing BUS grants.