Every indoor unit has filters behind its front panel that catch dust, hair and fluff before the air passes over the coil. When they clog, the unit has to work harder to move the same air, cooling and heating drop off, and dust starts to build up on the parts you can’t reach.
Cleaning them is simple on most wall-mounted units. Here’s how to do it safely, how often to check them, what the other filters in some units are for, and which jobs should be left to an engineer.
How often to check them
Your user manual gives the manufacturer’s recommendation for your model, so start there. As a rule of thumb, check the filters every few weeks when the system is used daily, and less often in quieter months. Homes with pets, smokers, nearby building work or a busy road need more frequent cleaning.
Many units have a filter reminder light. Treat it as a reminder, not a measurement: if the filters look grey and fluffy, wash them, whatever the light says.
Before you start
- Switch the unit off with the remote, then turn off the isolator switch near the unit, if there is one.
- Use a stable step or stepladder. Most wall units are high up.
- Have a towel ready and lay a dust sheet if the unit is above furniture.
- Check the manual for how your front panel opens. Most lift up from the bottom edge; some unclip.
Step by step
- Open the front panel. Lift it gently from both sides until it stays up or clicks into its open position.
- Slide out the filters. They’re usually two mesh panels. Lift them slightly at the tab and pull down and out. Note how they sit.
- Remove loose dust. Vacuum the dusty side with a soft brush attachment.
- Rinse. Run lukewarm water through from the clean side, so dust is pushed out the way it came in. Use a little mild washing-up liquid only if they’re greasy, then rinse well.
- Dry. Shake off the water and leave them to dry in the shade. Don’t put them in direct sun, on a radiator or use a hairdryer: heat can warp them.
- Refit. Slide them back in the right way round, making sure they sit fully in their guides.
- Close the panel, switch back on and reset the filter light if your model has one.
Want it done properly? AirCon Doctor installs, repairs and services air conditioning and heat pumps across London and the South East, from our base in East Grinstead. We’re an F-Gas certified company and NICEIC approved. Get a fixed-price quote.
The other filters in some units
Some models have extra filters behind or clipped to the mesh: deodorising, ioniser, silver or other air-cleaning filters. These often can’t be washed in the same way, and some need replacing at set intervals. Check the manual before wetting them, and buy replacements from the manufacturer or its stockists.
Cassette, ducted and floor units
A floor console is usually easiest: the filters sit behind the front grille. A ceiling cassette has filters behind its central grille, which hinges down; you need a safe platform and a second pair of hands. A ducted unit often has its filter behind a return air grille in the ceiling or wall, or in the unit itself in a loft or void. If you can’t reach it safely, leave it for a service visit.
What not to do
- Don’t run the unit without its filters, even for a day. Dust goes straight onto the coil.
- Don’t spray cleaners, disinfectants or air fresheners into the unit. They can damage parts and leave residue on the coil.
- Don’t poke at the coil fins behind the filter; they bend easily.
- Don’t pressure-wash the outdoor unit. Clear leaves and debris by hand with the power off, and keep plants trimmed back.
What a service adds
Filter cleaning keeps the air path clear, but it doesn’t reach the coil, the fan wheel, the drain tray and drain line, the electrical connections or the refrigerant circuit. A professional service checks and cleans those, tests performance and, where it’s required, carries out the F-Gas leak check. Our annual service costs £95–£150 + VAT. See air conditioning servicing or our guide to what an annual service includes.
If the unit smells musty even with clean filters, the coil or drain may need attention: see why air conditioning smells.
Quick answers
How often should I clean my air conditioning filters?
Follow your manual, but check them every few weeks during daily use and more often with pets or dust. Clean them whenever they look grey or clogged.
Can I wash air conditioning filters in water?
The standard mesh filters, yes: lukewarm water from the clean side, then dry in the shade. Check the manual before wetting any special air-cleaning filters.
Can I run the unit while the filters dry?
It’s best not to. Without filters, dust goes straight onto the coil and fan.
Do I still need a service if I clean the filters?
Yes. A service cleans and checks the coil, fan, drain, electrics and refrigerant circuit, which filter cleaning doesn’t reach.
Related services
More advice
- Air Conditioning Annual Service: What’s Included and Why It Matters
- Why Does My Air Conditioning Smell?
- How to Prepare Your Air Conditioning for Summer: 5 Essential Checks
- Can Air Conditioning Improve Air Quality?
- All advice
This guide is general information, checked against the sources linked on 30 October 2026. It isn’t legal, tax or financial advice. Rules, grants and product ranges change, so check the current position before you rely on it.