How Often Does a Heat Pump Need Servicing?

Most manufacturers ask for an air source heat pump to be serviced once a year, and many make an annual service a condition of the warranty. A heat pump has no burner, flue or gas supply, so there is no gas safety check, but it still has a fan, a refrigerant circuit, electronics and a full wet heating system behind it, and all of those need looking at. Check your warranty paperwork: if it says annual servicing, a missed year can give the manufacturer a reason to refuse a claim.

The service is not only about the box in the garden. A good share of heat pump complaints, such as rooms that never quite get warm or bills that creep up, come from the water side of the system: a blocked strainer, low pressure, dirty water or radiators that are out of balance.

Is an Annual Service Actually Necessary?

Yes, in most cases. Heat pumps are low-maintenance compared with a gas boiler, but low-maintenance is not no-maintenance, and the warranty terms usually settle the question for you.

A heat pump works hardest in exactly the conditions that clog it up: cold, damp weather with leaves blowing about. The outdoor coil gathers debris, the condensate drain that carries away defrost water can block, and small changes in refrigerant charge or sensor readings reduce efficiency without anything obviously breaking. Because a heat pump fails gradually rather than suddenly, the first sign of trouble is often a higher electricity bill, not a cold house. An annual check catches that drift early. If your unit is out of warranty, an annual service is still the sensible default; stretching it longer saves little and risks paying more to run a unit that is quietly underperforming.

What a Heat Pump Service Should Cover

A thorough service checks the outdoor unit, the refrigerant circuit, the electrics and controls, the hot water cylinder and the heating water. Ask for a written record of what was checked and the readings taken.

• Outdoor unit: fins and coil cleaned and straightened, fan and fan motor checked, mountings and anti-vibration feet inspected, and the condensate drain cleared so defrost water cannot freeze into a block of ice under the unit.
• Refrigerant circuit: operating pressures and temperatures checked against the manufacturer's figures, and a visual check for signs of leaks. Only someone qualified to handle refrigerants should open this circuit.
• Electrics and controls: connections checked, fault history read from the controller, and the settings reviewed, including the weather compensation curve and flow temperature.
• Hot water cylinder: the immersion heater and any anti-legionella cycle checked, and, on an unvented cylinder, the safety valves and expansion vessel tested.
• Heating water: system pressure, the strainer or magnetic filter cleaned, water condition tested, and the antifreeze concentration checked if the system uses glycol.

If the engineer only looks at the outdoor unit and leaves, you have had half a service.

Why the Water Side Matters So Much

Heat pumps run at lower water temperatures than boilers and rely on good, steady flow through every radiator or underfloor loop. Anything that restricts that flow costs efficiency straight away.

Most heat pumps have a strainer or filter on the return pipe to protect the heat exchanger. As it fills with debris, flow drops, the unit works harder, and some models will throw a low-flow fault. The same is true of magnetite sludge from older radiators and pipework, which is common when a heat pump has been connected to an existing system. Our guide on what a magnetic filter does explains why that protection matters. Pressure needs checking too: a sealed system that keeps losing pressure has a leak or a failing expansion vessel, and topping it up with fresh water every few weeks brings in oxygen that speeds up corrosion. Finally, a system that was never balanced, or has been altered since, leaves the rooms furthest from the unit short of heat. A radiator balancing visit is often the fix when the heat pump itself is running correctly.

Who Can Service a Heat Pump?

Ideally the installer, or an engineer trained on that manufacturer's units. The refrigerant circuit must only be worked on by someone who holds the right refrigerant handling qualification, which for most units means F-gas certification.

A Gas Safe registered engineer is not automatically qualified to service a heat pump, because the skills are different. Some heating engineers hold both sets of qualifications; many do not. If your heat pump was fitted under the Boiler Upgrade Scheme, it will have been installed by an MCS certified installer, and they are usually the first people to ask. Check whether your warranty names who can carry out the service, because some manufacturers only accept their own engineers or approved installers. Larger systems can also fall under legal leak-check rules for refrigerants; the installer can tell you whether yours does.

What You Can Check Yourself Between Services

You can keep the outdoor unit clear, watch the pressure gauge and note any fault codes. Do not open the unit, and do not try to top up or release refrigerant.

• Keep leaves, snow, plants and garden furniture away from the outdoor unit so air can flow through it freely. Never cover it to protect it from the weather.
• Some ice and steam in winter is normal: the unit defrosts itself periodically. A thick layer of ice that never clears is not normal and needs looking at.
• If your system has a pressure gauge, note the normal reading and call someone if it keeps dropping.
• Write down any fault code before resetting anything, and read your electricity usage now and then. A steady rise with no change in how you heat the home is a warning sign.

Signs Your Heat Pump Needs Attention Now

Rising running costs, rooms that no longer reach temperature, new noises, persistent ice or repeated fault codes are all reasons to book a visit rather than waiting for the annual service.

A heat pump that runs almost constantly without getting the house warm, a grinding or rattling fan, water pooling under the unit or hot water that takes much longer than before all point to a problem that will only get more expensive if left. If the controls have been changed, for example the flow temperature turned up to make up for a cold room, it is worth finding out why the room was cold in the first place, because turning the temperature up cuts efficiency. Rooms that stay cold even when the heat pump is running properly often point to radiators that are too small for low-temperature heating; our article on whether your radiators are big enough for a heat pump covers how to check.

Heat pump running but the house still not warm? We look after the water side of the system: filters, pressure, water condition, radiators and balancing. We will tell you plainly whether the problem is in the heating system or needs your heat pump installer. Get in touch to arrange a visit.