How often should you clean a window air conditioner?
Updated July 2026
Rinse a window air conditioner's filter every month during cooling season, and deep-clean the coils, drain pan, and blower once a year. The washable front filter is the part that clogs fastest, and because a window unit sits right in the room, everything it fails at happens where you breathe: it loses cooling power, the coil ices over, and mold in the standing pan water blows straight into the room. A five-minute monthly rinse prevents all three.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Filter, in daily summer use | Every month | The reusable mesh loads with room dust fast |
| Filter, light or bedroom-only use | Every 4–6 weeks | Slower loading, but still a monthly habit in season |
| Coils and drain pan | Once a year | A season of grime cuts capacity and breeds mold in the pan |
| Coil ices over during a run | Clean filter and coils now | Restricted airflow freezes the condensate on the coil |
| Musty smell when the unit runs | Clean pan and coils | Mold is growing in the standing pan water |
| End of season, before storage | Full clean and dry out | Storing it damp guarantees mold over the winter |
The cost of skipping it
What skipping it costs: a dirty window unit is mostly a comfort and health tax rather than a big repair. Airflow drops, the room never quite cools, and the unit runs longer for less, so the electric bill climbs. Choke the airflow enough and the coil freezes into a block of ice that can stress the compressor. The real cost is the mold: a slimy drain pan and coil turn the unit into a fan that blows spores into the room. When a $150–500 unit gets that far, replacement usually beats a deep repair.
How to do it (5 minutes filter · 45 minutes yearly deep clean)
- Unplug the unit before touching anything.
- Pop off the front grille, pull the foam or mesh filter, and rinse it under warm water until it runs clear, then let it dry fully.
- Once a year, remove the unit from the window (or slide out the chassis) and vacuum the front evaporator and rear condenser coils, straightening bent fins with a fin comb.
- Clean the drain pan and channels with water and a little vinegar to kill mold and clear the weep hole so water drains out the back.
- Wipe the blower wheel and cabinet, and check that the foam window seals are intact.
- Dry everything, reassemble, and store it upright and covered if the season is over.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing window AC cleanings schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
Why is my window air conditioner freezing up?
The usual cause is restricted airflow, and a clogged filter is the first suspect: too little air over the coil lets its surface drop below freezing so condensation turns to ice. Clean the filter and coils first. If it still ices with clean airflow, the unit may be low on refrigerant, which is a sealed-system issue you cannot top off like a car, or you are running it when it is too cool out (below about 65°F). See recharging refrigerant for why low charge is rarely the real answer.
Can a dirty window AC make me sick?
It can degrade your air. A window unit with a mold-filled drain pan and grimy coil blows those spores and that musty smell directly into the room, which bothers anyone with allergies or asthma. Unlike central AC, there is no ductwork between the mold and you. The fix is the yearly pan-and-coil clean with a vinegar or mild bleach rinse, plus the monthly filter, so the air the unit pushes out is cool and clean, not fuzzy.
How do I clean the coils on a window air conditioner?
Unplug it and pull the chassis out of the cabinet so you can reach both coils: the evaporator behind the filter and the condenser at the back. Vacuum the loose dust, then use a coil brush or a no-rinse coil cleaner on the fins, straightening any you bent with a cheap fin comb. Clear the drain pan and weep hole while you are in there. Let everything dry before you slide it back, since trapped moisture is what grows the mold you just removed.