Last Updated on March 25, 2021 by HVAC

How often to change your furnace filter?

There really are a LOT of variables when trying to decide how often to change your furnace filters. It has to do with the type of filter it is, it’s MERV rating, the local weather conditions, and of course how often you actually use your furnace to heat your home.

But the tables below should help you understand the best times to change them so you’re not wasting your time or money.

The Importance of HVAC Maintenance

Changing your furnace filter is important for many reasons. First is simply that there is a lot more dust particles and other airborne contaminants in your home than you think there are.

Have you ever noticed when the sun shines through your windows just right that you can see things floating in your air?

This is real “stuff” floating around and yes, you’re breathing it all into your lungs.

And if your filters aren’t clean, then all of this flotsam and jetsam is just being thrown right back into your air! And then into your body. Not a good thing by any means!

Not only is there the personal cost of bad health for you and your family, you also need to assess the out-of-pocket costs as well.

A dirty filter means your heating system is working a lot harder to generate heat. That’s more electricity or gas being used which results in higher energy bills. And that’s regardless of their MERV rating.

Then there’s the wear and tear on your unit. It takes a toll. And it results in higher maintenance furnace repair costs and even early replacement of your heating and cooling system.

So how do you know how often and when you should change the filters in your home? There are some general guidelines that can help you so that your HVAC system is running as efficiently as possible.

Do you have animals?

Animals affect when and how often your filters needs to be changed. If you have multiple animals then you will change your furnace filters more often than if you have none. Generally those with multiple animals will change a one or two inch filter every month.

A four inch filter will need to be changed every two months and a five inch filter every three months. If you only have one animals then you can change that and change the filters every two, four and six months depending on the size of your filter. No animals means you can change every three, six and twelve months.

How dusty is your home?

Dust is another thing that can affect the performance of your filter. If you get a lot of dust in your home then you will want to change more often. For one and two inch filters you need to change once a month. Four inch filters can go two months and five inch filters can go three.

Moderate dust will change those numbers to two, four and six. If you have no dust and no other factors then you change your filter every three, six or twelve month depending on the thickness.

Do you keep the heat or a/c fan on?

If you always have it on then you will want to change your one and two inch filters monthly. If you sometimes have it on, they can be changed every couple of months. If it is never on you can wait three months.

Four inch filters will be changed every two, four or six months depending on whether the fan is on constantly, sometimes or rarely. Five inch filters will be three, six and twelve months.

Does anyone smoke in the home?

Smoke can be detrimental to the filter and will cause you to have to change it sooner. Multiple smokers means that one to two inch furnace filters should be changed monthly, four inch filters every two months and five inch filters every three months.

One smoker changes those numbers to two, four and six. If there are no smokers then filters can be changed every three, six or twelve months based on the thickness of the filter.

Do you keep windows and doors open?

Since this lets a lot of dust and dirt inside, it can impact how often a filter should be changed. If the doors and windows are open a lot, change those one and two inch filters monthly. Change four inch filters every two months and five inch filters every three months.

If you only keep them open sometimes then you can change every two, four and six months. If you never have them open then you change filters at three, six and twelve months based on your thickness.

When you change your filter is based on more than simply your filter. While the thickness plays a prominent role, so do the factors in your home.

And if you’re unsure how to change the air filter in your home, check out our guide.

If you’re still not clear on when to change your furnace filter, or I haven’t gone into enough depth on the subject, please leave me a comment and I will try to answer your questions as best as I can.