Heat Pump Annual Service: What's Checked?

Like a boiler, a heat pump needs an annual service to keep it running efficiently and to catch small issues before they become expensive failures. Unlike a boiler service, however, many homeowners are unsure what a heat pump service actually involves — partly because the technology is newer to the UK market and partly because the checks are quite different.

This guide explains exactly what a qualified engineer checks during a heat pump annual service, why each check matters, how much you should expect to pay, and what happens if you skip servicing altogether.

Why Annual Servicing Matters

A heat pump is a mechanical system with moving parts, refrigerant under pressure, and electrical components that experience thousands of operating hours each year. Regular servicing achieves three things:

Maintains efficiency: A poorly maintained heat pump can lose 10 to 25 percent of its efficiency over time, directly increasing your electricity bills.
Prevents breakdowns: Most major failures are preceded by early warning signs that an experienced engineer can spot during a routine service.
Protects your warranty: Most manufacturers require annual servicing as a condition of their warranty. Skip a service and you may void your coverage for the most expensive components.

Given that a service costs between £100 and £200, the return on investment is considerable when you consider that a compressor replacement alone can cost £1,500 to £3,000.

The Complete Service Checklist

A thorough heat pump service covers the outdoor unit, indoor components, refrigerant circuit, electrical systems, and controls. Here is what a competent engineer will check.

Outdoor Unit Inspection

The service begins with a visual and physical inspection of the outdoor unit:

General condition: Checking for physical damage, corrosion, loose panels, or signs of wear
Coil condition: The evaporator coil must be clean and free from dirt, leaves, cobwebs, and other debris that restrict airflow. A blocked coil forces the system to work harder and reduces efficiency significantly.
Fan operation: The engineer will run the fan and listen for bearing noise, vibration, or wobble that indicates wear
Clearances: Checking that vegetation, fencing, or stored items have not encroached on the unit. Heat pumps need clear airflow around them — typically at least 300mm on all sides and more at the discharge (top or front, depending on model).
Base and fixings: Ensuring the unit is level, stable, and that anti-vibration mounts are intact
Condensate drain: Verifying the drain is clear and flowing freely. A blocked condensate drain can cause water to pool around the unit or freeze in winter.

Refrigerant System Checks

The refrigerant circuit is the core of the heat pump. These checks must be performed by an F-gas certified engineer:

Pressure checks: The engineer connects pressure gauges to the refrigerant circuit to verify that high-side and low-side pressures are within the manufacturer's specified range. Abnormal pressures indicate a leak, blockage, or component issue.
Temperature readings: Measuring superheat and subcooling values tells the engineer whether the system has the correct refrigerant charge. Too much or too little refrigerant both reduce efficiency and can damage the compressor.
Leak detection: Visual inspection of all refrigerant connections, brazed joints, and the compressor for signs of oil staining (which indicates a refrigerant leak). Some engineers use electronic leak detectors for a more thorough check.
Pipe insulation: Checking that refrigerant pipe insulation is intact and not degraded by UV exposure or weather

If a refrigerant leak is found, this becomes a separate repair job with additional costs. The service itself does not typically include topping up refrigerant — if the system needs a recharge, that indicates a leak that must be found and fixed first.

Filter Cleaning and Replacement

Heat pumps have filters in several locations:

Heating circuit strainer: A mesh filter on the water circuit that catches debris from the pipework. This should be removed, cleaned, and refitted. A blocked strainer reduces water flow and can cause the heat pump to lock out on flow errors.
Magnetic filter (if fitted): Many installations include a magnetic filter (similar to a MagnaClean on a boiler system) to capture magnetite sludge from radiators. This should be cleaned during the service.
Air filters (on some models): Some heat pump models, particularly air-to-air units, have washable air filters that need cleaning

Electrical Checks

Electrical safety and performance checks include:

Supply voltage: Verifying that the electrical supply to the heat pump is within the manufacturer's specified range
Current draw: Measuring the compressor's running current and comparing it to the rated value. Higher than normal current draw can indicate a failing compressor or refrigerant issue.
Wiring connections: Tightening all electrical connections. Vibration from the compressor can loosen terminals over time, creating resistance, heat, and potential fire risk.
Earth continuity: Checking that the earth connection is sound
Isolation switch: Verifying that the local isolation switch operates correctly
Capacitors: Testing run and start capacitors where applicable, as these degrade over time and can cause starting problems

Controls and Settings Review

A good service includes a review of the system's operating settings:

Flow temperatures: Checking that the heating flow temperature is set appropriately for the property. Many heat pumps are set too high during installation, wasting energy. A well-insulated home with modern radiators or underfloor heating may only need flow temperatures of 35 to 40 degrees Celsius.
Weather compensation curve: Verifying that the weather compensation settings match the property's actual heat demand. This curve adjusts the flow temperature based on outside temperature and is crucial for efficiency.
Hot water settings: Checking that the hot water cylinder temperature is set correctly — typically 48 to 52 degrees Celsius for heat pumps, with a periodic legionella pasteurisation cycle to 60 degrees.
Timer schedules: Reviewing heating and hot water schedules to ensure they are sensible. Heat pumps work best with longer, lower-intensity heating periods rather than the short, high-blast approach common with gas boilers.
Error log review: Most modern heat pumps store a log of error codes and operating data. The engineer should review this for patterns that indicate developing problems.

Indoor Components

The service also covers components inside the property:

Hot water cylinder: Checking the cylinder thermostat, immersion heater (if fitted), temperature and pressure relief valve, and expansion vessel
Buffer tank (if fitted): Checking operation and temperature
Circulation pump: Verifying the central heating circulation pump is operating correctly and on the right speed setting
System pressure: Checking heating system pressure and topping up if necessary. Repeated pressure loss indicates a leak in the heating circuit.
Expansion vessel: Checking the pre-charge pressure on the expansion vessel. A failed expansion vessel causes pressure fluctuations and can lead to water discharge from the pressure relief valve.

How Long Does a Service Take?

A thorough heat pump annual service typically takes one to two hours. If the engineer rushes through in 30 minutes, they are not checking everything. Conversely, if it takes significantly longer than two hours, they may have found an issue that needs further investigation.

Some service contracts include a written report detailing everything checked, any issues found, and recommendations. This is worth requesting even if it is not standard — it provides a record for warranty purposes and helps you track your system's condition over time.

How Much Does a Heat Pump Service Cost?

In 2026, you should expect to pay:

Basic annual service: £100 to £150 — covers all the standard checks listed above
Comprehensive service with report: £150 to £200 — includes a detailed written report and system performance analysis
Annual maintenance plan: £120 to £200 per year — some installers and specialist companies offer plans that include the annual service plus priority callout for breakdowns

These prices do not include any repair work identified during the service. If the engineer finds a fault, they will quote separately for the repair.

Who Should Service Your Heat Pump?

Your heat pump should be serviced by an engineer who is:

F-gas certified: Essential for any work involving the refrigerant circuit. This is a legal requirement under UK F-gas regulations.
Manufacturer trained: Ideally trained on your specific brand of heat pump. Different manufacturers have different service requirements and diagnostic procedures.
MCS certified (ideally): While MCS certification is primarily for installations, an MCS-certified company will have the technical competence for servicing.

Your original installer is often the best first choice for servicing. They know the system, the installation, and any quirks specific to your property. If your installer is no longer trading, contact the heat pump manufacturer for their list of approved service engineers in your area.

What Happens If You Skip Annual Servicing?

Skipping services does not cause immediate catastrophe, but the consequences accumulate:

Year 1 missed: Probably no noticeable effect, but efficiency may begin to drop as the coil collects dirt and settings drift
Year 2-3 missed: Efficiency losses of 5 to 15 percent are common. Your warranty is likely voided. Small issues that could have been caught early may develop into more serious faults.
Year 4+ missed: Risk of major component failure increases substantially. A blocked strainer or degraded electrical connections can cause secondary damage that turns a £100 service into a £1,000+ repair bill.

When Is the Best Time to Book a Service?

The ideal time to service your heat pump is in early autumn — September or October — before the heating season begins in earnest. This ensures your system is in peak condition when you need it most and gives time to arrange any repairs before cold weather arrives.

Avoid booking in the middle of winter when engineers are busiest with breakdowns and response times are longest. Spring is a reasonable alternative if you missed the autumn window.

Frequently Asked Questions

Do heat pumps need servicing every year?

Yes. Manufacturers recommend annual servicing, and most warranties require it. The cost of an annual service (£100 to £200) is small compared to the potential cost of an undetected fault developing into a major failure. Think of it as insurance for a system that cost £10,000 or more to install.

Can I service my heat pump myself?

You can carry out basic maintenance tasks such as keeping the outdoor unit clear of debris, checking system pressure, and cleaning accessible filters. However, the full annual service — particularly refrigerant checks and electrical testing — must be done by a qualified, F-gas certified engineer. DIY attempts risk voiding your warranty and breaking the law if you handle refrigerant.

Is a heat pump service the same as a boiler service?

No. While there are similarities (checking controls, testing safety devices, verifying efficiency), a heat pump service involves refrigerant circuit checks that require different qualifications and equipment. A gas-safe boiler engineer is not qualified to service a heat pump unless they also hold F-gas certification and have heat pump training.

What should I do between services?

Keep the area around the outdoor unit clear of leaves, grass cuttings, and other debris. Check the condensate drain is not blocked, especially in winter. Monitor your heating system pressure gauge and top up if it drops below the recommended level. Report any unusual noises, error codes, or changes in performance to your service engineer promptly.

Does annual servicing reduce energy bills?

Yes. A well-maintained heat pump operates at or near its designed efficiency. Dirty coils, incorrect refrigerant charge, or suboptimal settings can all increase electricity consumption by 10 to 25 percent. For a system costing £500 to £800 per year to run, that represents £50 to £200 per year in wasted electricity — often more than the cost of the service itself.

Will the engineer need access inside my home?

Yes. A full service requires access to both the outdoor unit and the indoor components — the hot water cylinder, controls, filters, and any buffer tanks or distribution equipment. Plan to be at home for the one to two hour appointment.