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How Often To Change Furnace Filter

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Frequency and Tips for Changing Your Furnace Filters

So, thinking over the main question "How often to change furnace filter?" one should consider the following factors:

  • What does the manufacturer recommend?
  • What does your Furnace and AC technician recommend?
  • What size of Filter are you using, such as 1 Inch, 2 inch, or 4 inch?
  • What brand are you using?

Understanding Filter Replacement Frequency

As indicated in my opening, you can see how this question is not just a one-size-fits-all; rather, it is a question that needs to be tailored to your needs.

However, the best place to start would be to go to the manufacturer's recommendation.

  • Carrier: recommends homeowners change their filters once every 30 days to 3 months.
  • Lennox: Recommends changing out the furnace AC filter once a month.
  • Rheem: Recommends you change your filters with their filter up to 90 days.

As you can see, changing and recommendation seem to be as nuanced as there are manufacturers. However, this at least gives you a starting place. And based on this information that we have thus far, we can see that on the best case one month and worst case 3 months.

HVAC technician opinions on this are as numerous as there are HVAC technicians. However, most HVAC technicians would likely be in the same ballpark as 1 to 3 months.

Clarifying Time-frames for Different Filter Thicknesses

Another factor to consider when figuring out when to change the furnace filter is the thickness of your filter.

The thickness of the filter will determine the frequency because technically, the filter has more fabric and can catch more. Of course, there is a drawback with using 2 inch and 4 inch filters. If you forget to change them in the recommended manner of 2 to 6 months, then you could run the risk of causing your furnace to shut down. Please check out our previous blog post on this.

Let’s clarify the time-frames for different filters:

  • For one-inch-thick filters, the recommendation is that you should replace them, ideally every 30 days to three months.
  • The filters command the lifespan of two inches thick, leaving homeowners asking how often they change the furnace filter for better efficiency, ranging from two months to four months.
  • It's claimed that these filters are as thick as four inches or even more. They should strategically be replaced between every three to six months, equaling the query "how often to replace furnace filter."

Adjusting to Environmental Conditions

The brand of filter that you are using above all will be the deciding factor. If you are using a cheap pack of 3 filters that cost you 4 dollars, then not only are you going to want to change them out quicker but one runs the risk of the filter not even doing the basics of stopping debris from going into the blower compartment.

However, an expensive 3M MERV 13 filter might be a bit on the overkill side, as the higher the MERV you go the more restriction you are placing on the furnace blower motor.

Yet, there is no question about it, I as a licensed HVAC technician would be more comfortable telling a homeowner to let their 1 inch MERV 8 filter be left in their furnace for 3 months.

A Honeywell filter I would be comfortable for around 6 to 12 months.

Five Season filters 12 months.

The brand of filter does matter, and I would argue that it comes down to the quality of the filter you're using.

Importance of Proper Filter Replacement

Equally important is the knowledge of "how to change furnace air filter." Done right, the replacement will improve the performance of your HVAC system while further strengthening the sanctity of indoor air quality.

Check out our YouTube video on how to change a furnace filter.

How Often To Change Furnace Filter

In Closing

Be sure that when you order your furnace replacement filters, you know what you expect to get from them.