How To Fix It

How Often You Should Change the Furnace Filter

A clean furnace filter keeps your HVAC system and your indoor air safe and healthy.

You should be changing the filter at least every 90 days. 1- and 2-inch filters and filters with a lower MERV rating should be changed up to once a month, as well as the ones used in houses with pets, small children, and people suffering from respiratory issues.

How Often to Change Furnace Filter?

A furnace filter is an incredibly important component that clears the air of various pollutants before it gets into the HVAC system. The air passes through the filter and the contaminants get ‘stuck’ there.

This component does contribute to the quality of the air you breathe. But the main job of an air filter is to protect the furnace from pollutants to prolong the system’s lifespan and to ensure that it operates efficiently.

In general, it is recommended to change your furnace filter every 90 days. However, it all depends on your specific situation.

How often your filter should be replaced would depend on quite a few different factors:

  • The thickness of the filter
  • The frequency of usage of the furnace
  • The number of people living in the house
  • Whether or not you have any pets
  • The type of the furnace, and so on.

Read: HVAC UV Light: Everything You Need To Know

How often should you change your furnace filter in the winter?

If you are going through a freezing winter and the system is in constant use, then you should consider replacing the filter more often than every 3 months.

In general, once a month should do, but, at times, you would have to change the filter every few weeks. Simply check the air filter and if it seems dirty, then replace it with a new one.

It is important to understand that winter is the time of the year when you rely on your furnace the most. So, it is better to be on the safe side and change the filter more often to make sure that your furnace doesn’t break down when you need it.

Read: Does Furnace Filter Size Matter?

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How often should you change your furnace filter in the summer?

Do you even need to replace your air filter in the summer, if you are not using your furnace?


Most of the HVAC systems consist of ducts. Heated air in the winter and cool air in the summer end up moving through the same ‘routes’ and the same filter.

So, just like in the winter, furnace filters have to be changed at least every 90 days in the summer. However, do remember that if you are using the HVAC system a lot, the filters would have to be changed more often (once a month).

Pollen can become an additional problem in the warmer time of the year. If you have anyone in the household who suffers from allergies, then this fact should also affect the frequency of filter change. 

How often to change 1 inch furnace filter?

1 inch air filter

In a nutshell, the thicker the filter, the longer it is going to last.

A 1-inch filter is the thinnest one, as you’ll usually find 1-, 2-, 4-, and 5-inch filters available on the market.

A general recommendation is that you have to change your 1-inch filter every 1-3 months.

Filter ThicknessThe Frequency of Replacement
1 inchEvery 1-3 months
2 inchesEvery 1-3 months
4 inchesEvery 6-9 months
5 inchesEvery 9-12 months

The thickness of your filter depends on the furnace’s filter slot. For example, you won’t be able to fit a very thick filter inside a small slot.

At the same time, it is also not advised to use the thinnest possible filter, as more air pollutants would be able to make their way into the HVAC system.

How often should you change a MERV 13 filter?

A Minimum Efficiency Report Value describes the filter’s ability to catch larger particles between 0.3 and 10 microns. The higher the rating, the better is the filter at catching such particles.

However, be careful as if the filter is too fine, it might end up forcing your furnace to work harder as it lessens the airflow.

Typically, MERV 13 is the highest rating appropriate for residential heating and it should be replaced every 9-12 months.

MERV RatingThe Frequency of Replacement
MERV 1-4Once a month
MERV 5-8Every 3 months
MERV 9-11Every 6 months
MERV 12-16Every 9-12 months

Read: Furnace Filter Airflow – What You Need To Know?

Should I Change My Furnace Filter Every Month?

Under certain circumstances, you might have to change your furnace filter every month. Especially, if you have pets, a few people living in the house, and if you tend to use your furnace quite often.

The great news is that it is relatively easy to figure out whether your filter needs to be changed or not.

Take a look at the filter. It is usually located in the blower compartment (where the return air enters the blower compartment).

If the filter appears very dirty, you can’t see the white pleats, and it has become grey or brown, then the time has come to change the filter.

Read: Why Does My Furnace Filter Get Dirty So Quickly

What Happens If You Don’t Change Your Furnace Filter?

A dirty air filter can end up causing a lot of problems. 

  • The furnace would have to work harder

When the filter gets dirty, it becomes harder for the air to move through it. As a result, the furnace would have to work a lot more to make sure that the same volume of air gets pushed through the HVAC system.

In such a case, a lot of parts of the furnace are going to wear out faster. Moreover, a hard-working furnace can easily overheat which can lead not only to the damage of the unit but also, in the worst-case scenario, to a fire.

Read: Why Gas Furnace Is Overheating?

  • Higher energy bills

If your furnace has to work harder, it ends up ‘eating up’ more electricity and/or fuel. Consequently, your energy bills are going to rise.

In fact, replacing a clogged filter with a new one can reduce your heating bills by as much as 15%.

  • The furnace can get clogged

If the filter is dirty, it won’t be able to filter out the dust and debris as efficiently, and more and more particles are going to enter the HVAC system.

The system’s fan is going to move all this dust through the system and the particles will end up getting stuck in small cervices and on different surfaces.

This can lead to such problems as short-circuiting and broken motors.

  • Air quality becomes worse

A great furnace filter can help you improve the air quality in your house, but a dirty air filter will do the opposite. 

Of course, even the cleanest homes have particles floating in the air, but as soon as the number of these pollutants increases, people living in the house can start suffering from a wide range of health issues.

The symptoms linked to poor indoor air quality include headaches, shortness of breath, fatigue, sinus congestion, allergies, nausea, dizziness, coughing, sneezing, and dryness and irritation of the eyes, throat, and nose

Если у вас грязный воздушный фильтр, вы также можете заметить, что на поверхностях в вашем доме всегда присутствует пыль, независимо от того, как часто вы его чистите.

Clogged filters also lead to constant temperature fluctuation and furnace shut down

Read: Does Furnace Filter Affect Air Conditioning?

Do Furnace Filters Really Last 3 Months?

A furnace filter can last for 3 months or even more, if… 

  1. You have a higher-end, thicker filter
  2. No one in the house has asthma and/or allergies
  3. You don’t have cats and dogs
  4. You don’t have small children
  5. You live in a place with a mild climate and use your furnace only for a few hours per day
  6. You live in a small house
  7. The overall air quality in your house is good