How to clean an air conditioner filter (window, portable and mini-split)

Step by step: how to clean an air conditioner filter

Safety first. Turn the air conditioner off and unplug it, or switch off the thermostat and breaker for a central or mini-split system, before you open any panel. Do not run the unit without its filter, and do not touch or bend the thin metal fins behind it; they are sharp.

1. 1

   Turn the unit off and unplug it

   Switch the air conditioner off and pull the plug for a window or portable unit. For a mini-split, turn it off with the remote and switch off its breaker if your manual tells you to before opening the front panel.

2. 2

   Open the front grille or panel

   On most window units, grip the front grille near the top on both sides and pull it toward you, or slide the filter out of a slot on the top or side. Mini-split indoor units have a front panel that lifts up to reveal two mesh filters. Check your manual if the grille does not move easily.

3. 3

   Slide the filter out and note its direction

   Pull the filter out gently. Look at which side faces the room, since that is the dirty intake side, and note any arrow or tab so it goes back the same way.

4. 4

   Vacuum off the loose dust

   Run the vacuum’s brush attachment over the dirty side of the filter. A gray felt layer should lift away. If the filter was only lightly dusty, this may be all it needs.

5. 5

   Wash it in warm soapy water

   Swish the filter in a sink of warm water with a few drops of dish soap and brush it gently with a soft brush or sponge. Rinse it from the clean side so the water pushes dirt back out the way it came in.

6. 6

   Let it dry completely

   Shake off the water, pat it with a towel, and let it air dry for an hour or two, out of direct heat. A damp filter in a cold air conditioner is an invitation to mildew.

7. 7

   Wipe the grille and look at the coils

   While the filter dries, wipe the front grille with a damp cloth. Look at the coil fins behind the filter: light dust can be removed with a soft brush moving along the fins, but heavy dirt, mold or bent fins are a job for a technician.

8. 8

   Reinstall and reset the filter light

   Slide the dry filter back in the same direction, close the grille, and power the unit on. If it has a filter reset or check filter light, press the reset button as your manual describes.

Which air conditioner filters can you wash?

Plastic mesh filters in window, portable and mini-split units are made to be washed. Pleated paper or fiber filters in central systems and furnaces are disposable and should be replaced, not rinsed.

Frigidaire’s instructions for its room air conditioners are to pull the grille forward, remove the filter, wash it in warm soapy water and let it dry completely, or vacuum it with a brush attachment. Consumer Reports recommends doing this a few times a season, and replacing a filter that is badly worn.

How often should you clean an AC filter?

Check it every month while the air conditioner is running, and clean or change it whenever you can see a layer of dust. Homes with pets, smokers or nearby construction need it more often.

ENERGY STAR advises inspecting, cleaning or changing the air filters in a central air conditioner, furnace or heat pump once a month, and warns that a dirty filter can raise energy costs and damage equipment. A clogged filter also lets dust bypass into the coils, which is harder and more expensive to clean than the filter.

Choosing a replacement filter for a central system

Buy the exact size printed on the old filter’s frame and the highest MERV rating your system can handle. If you are not sure what your system can handle, ask an HVAC technician.

• The EPA explains that a higher MERV rating traps more small particles, suggests at least MERV 13 if your system fan and filter slot can accommodate it, and says all filters need periodic replacement.
• Point the airflow arrow on the frame toward the furnace or air handler, away from the return grille.
• Write the date on the frame so you know when it went in.
• A musty smell when the AC starts usually comes from the coils or drain pan, not the filter. See our guide to getting rid of musty smells, and call a technician for mold on the coils.

Mistakes to avoid

• Washing a disposable pleated filter, which damages the media and lets dust through.
• Putting the filter back while still damp.
• Running the air conditioner without a filter while it dries, which pulls dust straight into the coils.
• Rinsing from the dirty side, which drives dust deeper into the mesh.
• Brushing across the coil fins and bending them flat.