Window air conditioners in Toronto homes work hard from May through September. A dirty filter and clogged evaporator coils reduce cooling efficiency — the unit has to run longer to achieve the same temperature, using more electricity and wearing faster. Cleaning a window AC unit at the start of the season and again mid-summer makes a real difference in performance and air quality.
Safety First: Unplug Before Cleaning
Always unplug the unit from the wall before any cleaning. Never spray water into an AC unit that is plugged in.
Cleaning the Filter (Monthly During Use)
The air filter is the most important and most frequently needed maintenance item.
- Remove the front panel of the AC unit — it typically snaps or slides off
- Slide out the filter (a mesh or foam panel)
- Hold the filter over a sink or garbage and tap gently to dislodge loose dust
- Rinse under warm running water from the clean side (rinse in the same direction air travels through the filter)
- For a heavily soiled filter, wash gently with mild dish soap, rinse completely, and squeeze out excess water — do not wring
- Allow to air dry completely before reinstalling — a wet filter causes mould growth
Some filters are disposable — replace rather than wash if the filter material is paper or non-washable media.
Cleaning the Evaporator Coils (Season Start and Mid-Season)
The evaporator coils — the fins visible behind the filter — collect dust and can develop mould in humid conditions.
- With the unit unplugged and filter removed, use a soft brush (a paintbrush or coil brush) to gently brush the fins in a downward direction — never bend the fins sideways as they're fragile
- Vacuum the brushed-off dust with a soft brush attachment
- Spray a coil cleaner (available at hardware stores — no-rinse AC coil cleaner is the simplest) onto the coils. It foams, loosens debris, and drains out through the drain pan
- Allow to work per the product instructions — typically 5–10 minutes
Cleaning the Drain Pan
The drain pan at the bottom of the unit collects condensation. If it has standing water and black slime, it has mould growing in it. Wipe it out with a cloth, clean with a vinegar solution, and rinse. Some drain pans have a drain hole that may need clearing with a pipe cleaner if water is backing up.
Cleaning the Exterior
Wipe the exterior housing with a damp cloth and mild cleaner. The exterior vents (the fins on the outside face) can be cleaned with a soft brush attachment on a vacuum.
End-of-Season Storage
Before storing for winter: clean the filter, wipe out the interior, and store covered or in a bag to prevent dust accumulation. Never store a unit on its side — the compressor oil can migrate.
Window AC cleaning is not part of a standard home clean but is included in some annual deep cleans. Book a Toronto deep clean — HST included.