Once a year. That is the interval heat pump makers ask for, and for many of them the warranty depends on it. For most homes it is not a legal requirement: a typical home heat pump holds too little refrigerant to fall under the annual F-gas leak-check rules. So the reason to service yearly is the warranty and the running cost, not the law.

That answers how often a heat pump should be serviced in one line. The detail is worth knowing, because the rules people hear about, from F-gas to landlord certificates, are often borrowed from gas boilers or big commercial systems and do not apply the same way to a heat pump in a house. Below: when the law does and does not require checks, what warranty terms say, and what the type of refrigerant changes. What a service actually involves, step by step, is on our heat pump servicing page.

How often should a heat pump be serviced to keep the warranty?

Every year, for the makes we have checked. Our servicing page quotes Mitsubishi Electric and Vaillant, both of which make an annual service a condition of their heat pump guarantees.

Panasonic's UK warranty terms for its Aquarea heat pumps say the same in more detail. Its standard three-year warranty requires the heat pump to be maintained annually by a suitably trained and qualified engineer. Its longer five and seven-year warranties require maintenance by an installer with the relevant Panasonic training, and if that does not happen the warranty falls back to the standard three years. Panasonic also requires records of maintenance to be kept, and says that failing to maintain the system, or to keep adequate records, will invalidate the warranty.

Two practical points follow. The clock starts at commissioning, so the first service is due within a year of the install, not a year after the first winter. And the record matters as much as the visit: keep every service sheet, and the logbook if your heat pump came with one, together and somewhere an engineer can find them.

For most homes, no. The legal duty people mean is the F-gas leak check, and it depends on how much refrigerant the system holds.

GOV.UK's guidance on checking F-gas equipment for leaks covers stationary heat pumps. It sets the minimum frequency by the size of the refrigerant charge, measured in tonnes of CO2 equivalent: the weight of refrigerant multiplied by its global warming potential. Equipment from 5 to under 50 tonnes CO2 equivalent must be leak-checked at least every 12 months. Below 5 tonnes, there is no set interval, and hermetically sealed systems have no set interval below 10 tonnes.

A home heat pump sits well under that line. R32, the refrigerant in many current units, has a global warming potential of 675. Mitsubishi Electric's service manual for its R32 Ecodan monobloc range, dated December 2023, lists a charge of 2.0 kg for the 5 kW model, 2.2 kg for the 6 kW and 3.0 kg for the 11.2 kW. Even the largest of those comes to about 2 tonnes CO2 equivalent: 3.0 kg × 675 = 2,025 kg. You would need around 7.4 kg of R32 to reach the 5-tonne line.

So the annual service on a home heat pump is not a legal leak check. It is still the visit where a leak would be noticed, and work on an F-gas refrigerant circuit has to be done by a certified company, which is why Heat Pump Energy holds REFCOM F-gas certification.

Does the type of refrigerant change how often it needs servicing?

Not the interval. It changes which rules apply.

Many newer heat pumps use R290, which is propane. Propane is not a fluorinated gas, so the F-gas leak-check rules do not apply to it at any size. R290 units still carry the maker's annual service requirement for the warranty, and they are serviced on the same yearly cycle. Older units may use R410A, and that one is different. Its global warming potential is 2,088, about three times R32's, so the 5-tonne line comes at roughly 2.4 kg of refrigerant. A larger R410A heat pump can hold more than that, and then an annual leak check is a legal requirement, not just a warranty one.

If you are not sure which refrigerant yours uses, the data plate on the outdoor unit names it, and so does the installation manual.

You can work it out from the data plate on the outdoor unit in under a minute.

  1. Find the refrigerant and its charge in kg. Both are on the data plate, and in the manual.
  2. If it is R290, stop there: it is not an F-gas, so no legal leak check applies.
  3. Otherwise, multiply the kg by the refrigerant's global warming potential, 675 for R32 or 2,088 for R410A, and divide by 1,000 to get tonnes of CO2 equivalent.
  4. Under 5 tonnes, there is no set legal interval. 5 tonnes or more, it must be leak-checked at least every 12 months.

A 2.2 kg R32 unit works out at about 1.5 tonnes. A 3 kg R410A unit works out at about 6.3 tonnes, which is over the line. If a leak check is required, keeping a record of each one is part of the duty, so file it with the service sheets.

Does the hot water cylinder need servicing too?

Yes, and it is easy to forget because it is not part of the outdoor unit. Most heat pump systems include an unvented hot water cylinder, which runs at mains pressure and relies on safety valves and an expansion vessel to stay safe. Bradford Council's guidance on unvented systems describes the annual service as inspecting and maintaining the safety valves, the pressure reducing valve and the expansion vessel.

Cylinder makers set their own warranty conditions, separate from the heat pump's. Joule's installation instructions, for example, make the 25-year guarantee on its stainless steel cylinders conditional on the cylinder being serviced every year and the service log book being filled in after each service. When you book the heat pump service, mention the cylinder, so its checks are covered on the same visit and recorded alongside.

Does a heat pump ever need servicing more often than once a year?

Not as a rule. The makers' schedules are annual, and a system that was designed and commissioned properly should not need more. Some checks within the service have a longer cycle of their own. Panasonic's warranty terms, for example, say the antifreeze in a properly maintained system may last more than seven years, but that it must be verified at each periodic maintenance to make sure it has not degraded.

What can bring a visit forward is a fault. A heat pump that is losing pressure, showing an error code or struggling to heat the house should be looked at when it happens, not saved for the annual service. Our heat pump and boiler repairs page covers the checks worth doing first and how to book a fault-finding visit.

What if the heat pump has gone years without a service?

Book one. The service itself is the same, and a first service after a gap usually turns up the gradual problems, the kind that build over several winters without anyone noticing, and the heat pump servicing page lists what gets checked. None of that is unusual, and catching it now is better than catching it on the coldest night of the year.

The warranty is a separate question. If the terms required annual servicing and it has lapsed, the cover may already be affected; the maker's terms are the only place to check that. Either way, getting back to a yearly service from now on protects the running cost, which is what a neglected heat pump loses first.

What about the boiler and the landlord's gas check?

If you have a gas boiler as well, or a gas hob or fire, those have their own yearly check. A landlord's annual gas safety duty applies to the gas appliances in a property, so a home heated only by a heat pump has no boiler on that certificate. The gas side is covered on our gas safety certificates page.

Mark services heat pumps across Doncaster and South Yorkshire from £150 a year, including homes in Rotherham. Book through the heat pump servicing page, or ring 07725 541383, Monday to Friday until 5pm.