Short answer: Most home air conditioning in London should be serviced once a year, ideally in spring before the first hot spell, with filters rinsed every few weeks in summer. Busy offices, dusty rooms and systems used all year for heating may need two visits. Larger systems over the F-gas threshold also need legal leak checks.
The short answer
| System | Suggested service | Between services |
|---|---|---|
| Home split, used in summer only | once a year, in spring | rinse filters every few weeks in summer |
| Home system also used for heating | once a year, or twice if used heavily | check filters monthly in use |
| Ducted home system | once a year | filter check via the hatch |
| Small office or shop | once or twice a year | filters monthly |
| Busy office, server or comms room | two or more visits a year | filters and alarms checked regularly |
| Larger systems above F-gas threshold | service plus legal leak checks at set intervals | records kept by the operator |
Your manufacturer’s manual and warranty terms take priority. Many extended warranties require a yearly service by a qualified engineer, and you should keep the service record.
Why spring is the right time in London
London’s hot spells can arrive suddenly. If a system has sat unused since September, the first time you need it might be a 28°C day in June, and that is when faults show up and engineers are busiest. A spring service means:
- clean filters and coils for full cooling from the first hot day
- a clear condensate drain before the unit starts producing water again
- any refrigerant or electrical faults found before you depend on it
The Met Office London City Pack projects summer maximum temperatures in London rising by 1.2 to 2.8°C by the 2030s, so systems are likely to be working harder over more weeks of the year.
Why city systems need it more
Indoor units recirculate room air through a filter and over a cold coil. In central London, that air carries more dust, traffic soot and pollen than in the countryside. Mansion flats in Kensington and Chelsea with windows over busy roads, and offices near main routes, often see filters clog faster than people expect. Outdoor units on rear walls and roofs collect leaves, grime and pigeon mess, which block airflow.
When airflow drops, the unit works harder for less cooling, uses more electricity, and in bad cases the indoor coil can ice up and then drip. Dirty coils and drain trays are also where musty smells start, which we cover in our guide to air conditioning smells and cleaning.
What you can do yourself
Between services, most owners can safely:
- switch off and lift the front panel to remove and rinse the filters in lukewarm water, letting them dry fully
- wipe the outside of the indoor unit with a damp cloth
- keep the area around the outdoor unit clear of leaves, plant pots and stored items
- check that water is not dripping from the indoor unit or staining the wall
Leave the coil, fan, electrics and anything to do with refrigerant to an engineer. Refrigerant work must be done by someone with an F-gas qualification working for a certified company.
The legal side
Under the F-gas rules, equipment that contains fluorinated gas equivalent to 5 tonnes of CO2 or more must be checked for leaks at regular intervals by a certified engineer, with records kept. Gov.uk sets out the frequency, which depends on the amount of gas and whether a leak detection system is fitted. Most single room home systems hold much less than this, so a yearly service is good practice for them rather than a legal requirement. Large multi zone office systems often do cross the threshold.
Separately, buildings with air conditioning of more than 12kW effective rated output need a TM44 inspection by an accredited energy assessor at least every five years, explained in the government guide. That applies to many London offices and some large homes.
Signs you should not wait for the yearly visit
Book a check sooner if you notice:
- weaker cooling or heating than last season
- water dripping from the indoor unit
- ice on the pipes or the indoor coil
- a musty or burning smell
- new rattles, buzzing or clicking
- error codes or flashing lights
Our air conditioning repair page explains the common faults.
Moving into a flat with air conditioning
Many London flats are sold or let with air conditioning already fitted, sometimes with no service history. Ask the seller, landlord or managing agent for the installer’s details, any service records and the warranty documents. If there is nothing, book a service before relying on it, so an engineer can check the refrigerant, drains and electrics. Our Kensington and Chelsea page explains the local rules if you are thinking of replacing an old system.
To book a visit, see our air conditioning servicing page.
Quick questions
Is it a legal requirement to service air conditioning?
Not for most home systems. Leak checks become a legal duty once a system holds refrigerant equal to 5 tonnes of CO2 or more, which mainly affects larger commercial systems. Offices over 12kW also need a TM44 inspection every five years.
How often should I clean my air conditioning filters?
Check them every few weeks when the unit is in regular use, and rinse them when dust builds up. Follow the manufacturer's manual for your model.
What happens if I never service my air conditioning?
Filters and coils clog, cooling drops, running costs rise, and drains can block and leak. Smells from dirty coils are also common on neglected systems.
Last updated 23 October 2026. Written for homes in London. Rules can change, so check the linked sources for the latest position.