Air conditioning deep clean & antibacterial treatment cost
A professional deep clean of an indoor air conditioning unit — chemical coil and blower-wheel clean, drain flush and antibacterial treatment — costs an indicative £60–£150 per unit in 2026, less when bundled with a service. Why units need it, what is involved, how often, where DIY stops.
Deep clean costs at a glance
| Job | Indicative cost (2026) | Notes |
|---|---|---|
| Deep clean and antibacterial treatment, one wall-mounted unit | £60–£150 | Per indoor unit; higher end for heavy soiling or blower-wheel removal |
| Deep clean added to a standard service | Lower combined rate | Unit already stripped; ask for a bundled price |
| Additional units, same visit | Lower per-unit rate | Travel and set-up shared |
| Standard service (for comparison) | £75–£150 | Whole-system check; see the servicing cost guide |
| Ducted, cassette or commercial units | Quoted per unit | Access, size and any duct cleaning drive the price |
Indicative ranges from UK engineer and maintenance-provider quotes, 2026. Prices vary with unit type, access and condition.
Why air conditioning units need a deep clean
Every time an air conditioner cools, its indoor coil runs below the dew point and water condenses on it. Room air drawn across that wet coil leaves fine dust behind, and in a warm, dark, damp box that is exactly what mould and bacteria want. Within a season or two the coil, blower wheel and drain tray carry a biological film that a filter rinse never touches.
The results are familiar: a musty smell on start-up, black specks on the louvres, reduced airflow despite clean filters, dripping because the drain has slimed up — and, for asthma or allergy sufferers, air blown across the room from a mouldy surface. Hygiene is the main reason to book a deep clean; the efficiency gain is a bonus. For the whole-system check that sits alongside it, see what a service includes.
What a deep clean and antibacterial treatment involves
A proper deep clean takes roughly an hour per wall-mounted unit — longer if the blower wheel comes out:
- Isolate and strip. Power off; front panel, filters, louvres and drain tray removed; electronics protected.
- Contain. A cleaning bib is fitted around the unit to catch run-off so the clean is done in place.
- Coil chemical clean. Coil cleaner applied to the evaporator fins, left to work and rinsed through.
- Blower wheel clean. The cylindrical fan is where most black growth sits; cleaned in place with chemical and brush, or removed and washed if heavily fouled.
- Drain tray and line. Tray cleaned, condensate line flushed, any pump tested.
- Antibacterial treatment. A disinfectant applied to coil, tray and housing to kill remaining growth and slow its return; some engineers add a slow-release drain tablet.
- Reassemble and test. Run in cooling to confirm airflow, drainage and no smell.
Cassette and ducted units follow the same principles with more work to reach the coil, so they are quoted per unit. Anything found while the unit is open — a cracked tray, a failing pump — is a repair, quoted separately; see our repairs page.
How often to deep clean
Most domestic units need a deep clean every one to two years, or whenever the smell comes back. Bedroom units, homes with allergy or asthma sufferers, kitchens, and any unit running long hours justify an annual deep clean — usually as an add-on to the spring service. Commercial units in restaurants, gyms, salons and healthcare settings are typically deep cleaned annually within the maintenance schedule.
Between deep cleans, clean filters are what extend the interval. To have it happen automatically each year, ask for it to be written into a maintenance contract; documented servicing is usually a warranty condition, and the servicing frequency guide covers the wider schedule.
What you can do yourself — and what to leave to an engineer
Safe DIY: wash the dust filters every month or two in heavy use; wipe the casing and louvres; vacuum the visible fins gently with a soft brush; keep the outdoor condenser clear. These cost nothing and genuinely slow the build-up.
Leave to a professional: the chemical coil clean, blower-wheel clean, drain flush and antibacterial treatment. The aluminium fins bend if brushed the wrong way, the PCB sits inches from the run-off, DIY aerosol cleaners rarely reach the blower wheel, and a clumsy strip-down cracks clips. If the unit is serviced at the same time, the refrigerant checks must be done by someone F-Gas certified — which is why the two jobs are usually bundled. All the engineers we match you with are vetted and F-Gas certified.
Frequently asked questions
Get deep clean quotes
Tell us how many indoor units you have and the problem — smell, black spots, dripping — and we match you with vetted, F-Gas certified engineers who quote for a deep clean alone or with a service. Free, no obligation.