When to Replace Furnace Filter

 Keeping Your HVAC System Safe, Healthy, & Efficient

How Often Should I Change My Furnace Filter?

The average furnace filter needs to be replaced around every 2-3 months, but the actual life of your filter varies widely based on your home's air quality and HVAC setup. As your air filter loads with dust, it restricts air flow, making your furnace work harder, which runs up your electric bill and decreases the life of your entire comfort system, so it's important to replace your filter before it becomes clogged. How often that should be done is easily our most frequently asked question. But the honest answer is that it depends on factors like the size of your home and system, the type of filter, and your air quality due to things like pets. We go through these factors in more detail below.

These Factors Affect Your Furnace Filter Life

  • Furnace Size

    A large 120kBtu furnace moves twice as much air as a smaller 60kBtu furnace, which means the filter for the larger furnace will get dirty twice as fast. Our Watkins comfort specialists always focus on ensuring you have the right size furnace for your home. A large home needs a large furnace, and a large furnace needs a lot of air. 

  • Filter Size

    Hey, this isn’t rocket science. A larger filter holds more dust. A typical 20x25x1 filter has nearly 30% more surface area than a 16x25x1 and, therefore, 30% more dust holding capacity. You can’t really change your filter size, as it needs to fit the rack that was installed with your furnace. However, you should take this into account when deciding on a filter schedule.

  • Dust Load in the Home

    Much of our house dust comes from living activity, and more people equals more dust. A family with large, hairy dogs can expect large, hairy furnace filters that get dirty much quicker. On the other hand, if you live alone, don’t smoke, keep a tidy house, and you don’t have a furry friend, you can easily double your filter life.

  • Filter Type

    We typically judge a furnace filter’s effectiveness by looking at it’s MERV rating. This rating ranges from 1 to 16, with the higher number indicate more allergen removal. The problem is that, while a MERV 16 filter stops very fine dust, it also stops air and can cause furnace overheating and A/C freeze-ups. A high MERV filter will load with dirt sooner, and will need to be replaced more frequently.

Our Recommendation for Changing Your Filter

In most cases, one-inch thick furnace filters need to be replaced every one to two months, no matter what the packaging says. In just over an hour, our technicians can work a little duct magic to replace your 1-inch filter rack with a real air cleaner. An Aprilaire filter has four-inch deep pleats to allow great airflow to your furnace. With a dust-holding capacity of more than a year, filter replacement is actually cheaper and much less hassle than a monthly trip to the hardware store.

Still have questions? Check out our page on Indoor Air Quality. We address the four main factors in a home that contribute to allergy symptoms.

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