After a summer of running the air conditioning hard, it’s almost time to turn our attention to essential HVAC maintenance ahead of fall. And if there’s one task our experts say you shouldn’t put off, it’s replacing a dirty air filter.
A clogged filter can force your system to work harder, reducing airflow and efficiency. In more extreme cases, it can even contribute to system failure. The good news? Replacing it is quick, simple, and relatively inexpensive, making it one of the easiest fall maintenance jobs to check off your list.
Here, HVAC pros share why it's a fall home maintenance tip that demands immediate attention.
As Vanessa Ferrara, Co-Owner of Dang It’s Hot!, a family-owned air conditioning company serving South Florida, explains, your air filter is your AC system's first line of defense against dust, pet hair, and other airborne debris.
'After a long, hot summer, especially in warmer climates like South Florida where the AC runs almost non-stop, a dirty filter can cause restrictions and reduce the airflow through the system,' she says.
'Restricted airflow can make your AC system work harder, run less efficiently, and in more severe cases, cause the system to freeze up. Checking the filter is a simple and inexpensive step to keep your system operating properly,' while avoiding dust and dirt increasing your energy bills.
Alex Marsh, CEO and Founder of Bearcat Heating & Cooling in Spokane, Washington, agrees. 'Think of the air filter like the oil in your car,' he stresses. 'You wouldn't run a full summer of hard driving and then skip the oil change before a road trip, but that's exactly what happens to most furnaces and ACs every fall.
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'And you're about to seal the house up for the season, with windows shut, everyone indoors, and the system recirculating the same air, so a fresh filter matters most exactly when fall allergens like ragweed and mold are peaking.'
How to Replace Dirty Air Filters
Fortunately, says Shawn Bell, General Manager, Operations of Texas Ace Service Heating & Air, 'Swapping air filters is one of the rare DIY maintenance tasks that requires no tools and minimal knowledge.'
To begin with, ensure your AC is turned off at the thermostat, and locate your filter. Then, simply remove the old filter from the filter slot and replace it with a new one of the same size.
'Match the filter to the printed dimensions on the old filter's frame, and insert it with the airflow direction arrow facing toward the unit,' adds Shawn. 'Filters are typically between one and three inches thick.'
More than anything, ensure you don't put the new air filter in backwards. 'The airflow arrow must point toward the furnace or air handler (the direction air travels, away from the room and toward the blower),' warns Alex. 'Putting it in backwards is the number one DIY mistake, and it chokes the exact airflow you're trying to protect.'
Then, turn your HVAC system back on, and write the date directly on the new filter when you install it, so you'll know roughly when it needs changing again.
'Don't rely only on the "change every 30 to 90 days" rule,' though, shares Vanessa. 'How quickly a filter gets dirty depends on the home, pets, how often the system runs, and even the time of year. Check it regularly and replace it when it's visibly dirty.'
What to Shop
While you'll need to shop for the exact air filter to fit your system, below I've curated a selection of six items that make it easy to clean your HVAC system in between replacing the filters.
All prices were correct at the time of publication.
This specifically designed cleaning brush features stainless steel pins to help remove trapped debris between fins and is a safe, eco-friendly alternative to chemical sprays.
MR.SIGA Microfiber Cleaning Cloths
A quick and simple wipe with a microfiber cloth can work wonders when it comes to keeping your filter looking clean and dust-free. These ones are ultra-soft, absorbent, and conveniently machine washable.
Seventh Generation Dish Soap Liquid
Reusable filters can be gently washed with dish soap and water, left to dry, and replaced. This dish soap is an EPA Safer Choice Certified Product and comes housed in a one hundred percent recycled bottle.
Use a handheld vacuum to clean dirt and debris from intake and return vents. This one is lightweight, portable, and rechargeable, with a rotating slim nozzle that helps you to clean tight, hard-to-reach spaces.
Air Conditioner Condenser Cleaning Brush
These cleaning brushes make it quick and easy to clean condenser fins and evaporators. Each is stiff and smooth enough to effectively clean away dirt, while the plastic handle is designed for a firm and comfortable hold.
AC Coil Cleaning Brush & Fin Cleaner Comb
This cleaning brush is designed to remove stubborn debris, dust, and soil buildup from AC evaporator and condenser coils. The stainless steel pin side removes compacted dirt and buildup, while the soft plastic bristle side sweeps it away.
Meet the Experts
Vanessa is the Co-Owner of Dang It’s Hot!, a family-owned air conditioning company serving South Florida. She oversees the operations and customer experience side of the business and works closely with homeowners and experienced AC technicians every day. Her work focuses on helping homeowners better understand their AC systems, preventive maintenance, and the practical steps they can take to improve comfort, efficiency, and system reliability.
Shawn is the General Manager, Operations of Texas Ace Service Heating & Air, a trusted HVAC company serving the Dallas–Fort Worth metroplex since 2012.
'Key Note: Match the filter to the system; jumping to the highest MERV can restrict airflow on equipment that wasn't designed for it, so check your specs first,' concludes Alex. 'For most homes, MERV 8 to 11 is the sweet spot, and skip the cheap fiberglass filters (MERV 1 to 4); they protect the fan but barely clean the air,' which is a common mistake compromising your home's air quality.
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