With summer temperatures rising and energy costs at all-time highs, a dirty window air conditioner is not only disgusting, but it’s also costing you money. Dust and debris force the compressor to work harder, while trapped moisture creates the perfect breeding ground for dangerous hidden mold. Whether you’re taking your window air conditioner out of
With summer temperatures rising and energy costs at all-time highs, a dirty window air conditioner is not only disgusting, but it’s also costing you money. Dust and debris force the compressor to work harder, while trapped moisture creates the perfect breeding ground for dangerous hidden mold. Whether you’re taking your window air conditioner out of storage or upgrading it in mid-summer, a thorough, thorough cleaning is the easiest way to ensure you get the freshest, coldest air out of your unit.
For our guide to the best air conditioners, I have tested and reviewed window air conditioners for five years. For this article, I spoke with two HVAC contractors: Ray Bramble, owner of Aire Serv of Bull Run and Aire Serv of the Central Shenandoah Valley, and Vincent Drago, owner of Mini King in Westchester County, New York.
How to clean a window air conditioning unit
You should thoroughly clean your window air conditioner at least once a year. The best time to clean is just before installing it for the season or immediately after removing it, as you can easily disassemble the unit.
You will need the following materials:
Clean the filter
Experts recommend cleaning an air conditioning filter with warm soapy water. James Brains/Business Insider
How often: When the “clean filter” light illuminates on the control panel or approximately once a month
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• Open the front grill: Unlatch and lower the front cover of your unit.
• Remove the filter: Gently slide or pull the mesh filter out of its slot.
• Remove loose debris: Take the filter outdoors and shake it, or use a handheld vacuum to remove dust.
• Wash and dry: Wash the filter in the sink with warm water and a few drops of dish soap or mild detergent. Let the filter air dry completely before reinstalling it. Never put a wet filter back into an air conditioning unit.
Deeply clean the coils and fins.
Spray hydrogen peroxide on the fins and coils. James Brains/Business Insider
How often: Annually or as needed
Deep cleaning your air conditioner involves cleaning the coils and fins. Window air conditioners have two sets of coils and fins: the condenser coils at the back and the evaporator coils at the front. Both can be accessed by removing the case from your unit.
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• Take it outside: Both Drago and Bramble recommend cleaning your air conditioner outdoors because it can get dirty.
• Remove the case: Remove the screws around the outer case (usually located towards the bottom edge of the unit. “Take out any screws that you see around the case. They will usually be more towards the bottom around the edges,” Drago said. Once you have removed the necessary screws, you can remove the face/control panel of the unit and pull the case up.
• Clean debris from the surface: use a vacuum cleaner or compressed air to remove loose dust from the interior.
• Comb the fins: Gently use a fin comb or soft bristle brush to remove debris from the delicate metal fins. Avoid touching them with bare hands as the bed is easily damaged.
• Apply cleaner: Cover all electrical components tightly with plastic to protect them from moisture. Spray the front (evaporator) and rear (condenser) coils and fins with 3% hydrogen peroxide. Let it sit for 10 minutes.
• Rinse gently: Using a garden hose, lightly spray the coils and fins to rinse them. Do not use high pressure water as it will instantly bend the aluminum fins.
Rub the inside
Before and after photos of preliminary cleaning the drip tray with a vacuum cleaner. James Brains/Business Insider
How often: Annually or as needed
• Vacuum the base: Use a handheld vacuum cleaner with a brush to vacuum up built-up dirt, dead bugs, and debris from the bottom tray.
• Protect electrical components: Double check that electrical components are still securely covered with plastic bags or wrap.
• Target mold areas: Spray the interior with 3% hydrogen peroxide, paying special attention to the drain pan and fan blades – that’s where mold is most likely to grow.
Rinse and drain: Hold the air conditioning unit at a slight angle so the water naturally drains out the back. Lightly spray the interior with a hose. “Maybe spray it one more time and get all that hydrogen peroxide out of there,” Drago said. “You don’t want that to sit there and have the wind blow back into the room.”
Clean the exterior
How often: Annually
As
• Wipe Clean: Wipe a damp microfiber cloth over the exterior shell and accordion side curtains.
• Scrub tough stains: For stuck-on dirt or sticky residue, use a soft-bristled brush and a mixture of warm water and a mild detergent.
How to Clean a Moldy Window Air Conditioning Unit
Drago recommended deep cleaning your window air conditioning unit if you discover mold, performing all the steps mentioned above. He noted that fan blades and the drip pan are common places where mold forms.
Drago highlighted the importance of using 3% hydrogen peroxide to scrub the interior. “That should kill most things,” he said.
How to Clean a Window Air Conditioning Unit Without Removing It
The safest way to thoroughly clean your window air conditioner is to remove it from the window, but that is not always possible. Fortunately, there are some cleaning tasks you can do with your air conditioner installed.
You can clean the front evaporator coils by removing the filter and front grille from your window air conditioner. Use compressed air to remove dust and debris from the fins. A soft bristle brush or finned comb will also work if you are careful and don’t bend the fins.
If you can access the air conditioner from outside, such as if it is installed on the first floor of a building, you can clean the condenser coil. You can use the dry method described above or clean with water using a spray bottle or hose with a nozzle. If you use water, make sure there is no power to the air conditioner and the water drains outside. If your air conditioner is angled correctly, the water should drain out.
Reassemble your air conditioner
Before reassembling your air conditioner, make sure it has dried, especially the filter. First, remove any plastic you used to cover the electrical components. Then put the case back on the unit. Loosely screw in all the screws. Once all the screws are in place, you can tighten them. Finally, you can reinstall the face/control panel and filter.
Insider Takeout
Cleaning your window air conditioner will extend its life, ensure it works properly, and save you money on energy costs. It may be painful the first time you do it, but it will get easier the more familiar you become with the process. Remember: An hour of effort will give you a summer of freshness.
If you’re frustrated with cleaning your window unit, you might want to consider one of the best portable air conditioners, which might be easier to clean. For a more detailed comparison, check out our guide to portable air conditioners vs window air conditioners.
Looking for a new air conditioner? Consider some of the picks from our best air conditioning guide:
Midea U Inverter Window Air Conditioner (MAW08V1QWT)
The Midea U Inverter window air conditioner features a unique design that allows you to leave the window open while it is installed. While it was recalled last year due to mold issues, the new 2026 version (MAW08V1UWT) addresses those issues with new drain plugs and external levelers.
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