With summer temperatures rising and energy costs at all-time highs, a dirty window air conditioner isn't just gross, it's actively 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 digging your window AC out of storage or giving it a mid-summer refresh, a thorough deep clean is the easiest way to ensure you're getting the freshest, coldest air from your unit.
For our guide to the best air conditioners, I've tested and reviewed window air conditioners for five years. For this article, I talked to two HVAC contractors: Ray Bramble, owner of Aire Serv of Bull Run and Aire Serv of Central Shenandoah Valley, and Vincent Drago, owner of Mini King in Westchester County, New York.
How to clean a window AC unit
You should clean your window air conditioner thoroughly at least once a year. The best time to clean is right before you install it for the season or right after you remove it since you can easily take the unit apart.
You will need the following materials:
- Warm water
- A mild detergent
- A pack of microfiber cleaning cloths
- Spray bottle with 3% hydrogen peroxide
- A fin comb
- A versatile screwdriver
- Protective gloves (optional)
- A can of compressed air (optional)
- One of our best vacuum picks (optional)
- An AC coil cleaner (optional)
Clean the filter
How often: When the "clean filter" light illuminates on the control panel or about once a month
How to
• Open the front grill: Unlatch and pull down 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 lift away dust.
• Wash and dry: Wash the filter in the sink using warm water and a few drops of dish soap or mild detergent. Allow the filter to air dry completely before reinstalling it. Never put a wet filter back into an AC unit.
Deep clean the coils and fins
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 in the back and the evaporator coils in the front. Both are accessible by removing your unit's case.
How to
• Take it outside: Both Drago and Bramble recommend cleaning your air conditioner outdoors because it can get messy.
• Remove the case: Take out the screws around the exterior case (usually located toward the bottom edge of the unit. "Take out any screws that you see around the case. Usually, they're going to be more toward the bottom around the edges," said Drago. Once you've removed the necessary screws, you can remove the face/control panel of the unit and pull the case straight up.
• Clear surface debris: Use a vacuum or compressed air to blow away 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 your bare hands, as the bed very easily.
• Apply cleaner: Tightly cover all electrical components with plastic to protect them from moisture. Spray the front (evaporator) and back (condenser) coils and fins with 3% hydrogen peroxide. Let it sit for 10 minutes.
• Rinse gently: Using a garden hose, lightly mist the coils and fins to rinse them. Do not use high pressure water, which will instantly bend the aluminum fins.
Scrub the interior
How often: Annually or as needed
• Vacuum the base: Use a handheld vacuum with a brush attachment to suck up accumulated dirt, dead bugs, and debris from the bottom pan.
• Protect electrical components: Double-check that the electrical components are still securely covered with plastic wrap or bags.
• Target mold zones: Spray the interior with 3% hydrogen peroxide, paying special attention to the drain pan and the fan blades — that's where mold is most likely to grow.
Rinse and drain: Hold the AC unit at a slight angle so water naturally drains out the back. Lightly spray down the interior with a hose. "Maybe spray it down one more time and get any of that hydrogen peroxide out of there," said Drago. "You don't want that sitting there and blowing back into the room."
Wipe down the exterior
How often: Annually
How to
• Wipe with a damp cloth: Run a damp microfiber cloth over the exterior casing and the accordion side curtains.
• Scrub stubborn spots: For stuck-on grime or sticky debris, use a soft-bristle brush and a mixture of warm water and mild detergent.
How to clean a window AC unit with mold
Drago recommended a deep clean of your window AC unit if you discover mold, performing all of the abovementioned steps. He noted that the fan blade and drip pan are common places where mold forms.
Drago stressed the importance of using 3% hydrogen peroxide to scrub the interior. "That should kill most things," he said.
How to clean a window AC unit without removing it
The safest way to thoroughly clean your window air conditioner is to remove it from the window, but that's not always possible. Fortunately, there are some cleaning tasks you can do with the AC installed.
You can clean the front evaporator coils by removing the filter and front grill of your window AC. Use compressed air to blow dust and debris from the fins. A soft bristle brush or fin comb will also work if you are gentle and don't bend the fins.
If you can access the AC from the outside, like, for example, if it's 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 attachment. If you use water, make sure there is no power running to the AC and that the water will drain outside. If your AC is angled correctly, the water should drain outside.
Reassemble your AC
Before you reassemble your air conditioner, make sure it has dried, especially the filter. First, remove any plastic you may have used to cover the electrical components. Then fit the case back onto the unit. Loosely screw in all of the screws. Once all of the screws are in place, then you can tighten them. Lastly, you can reinstall the face/control panel and the filter.
Insider's takeaway
Cleaning your window air conditioner will extend its lifespan, ensure it functions properly, and save you money in energy costs. It may be a pain 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 coolness.
If you're frustrated with cleaning your window unit, you might want to consider one of the best portable air conditioners, which could be easier to clean. For a more in-depth comparison, check out our guide to portable air conditioners vs. window air conditioners.
Looking for a new air conditioner? Consider a few of the picks from our best air conditioner guide:
The Frigidaire Inverter Window Room Air Conditioner (FHWW145WE1) is the best air conditioner for large rooms, decreasing our sizable test room by four degrees in an hour and featuring an easy setup.
The Midea U Inverter Window Air Conditioner features a unique design that lets you leave the window open while it's installed. While it was recalled last year due to mold concerns, the new 2026 version (MAW08V1UWT) addresses those issues with new drain plugs and external levelers.
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