How Often Should You Change Your Furnace Filter?

When it comes to maintaining a healthy central air system in your house, most homeowners are aware that they need to regularly change their AC air filters. However, they may not be aware that they also need to change their furnace filter at regular intervals.

Most homeowners forget to change their furnace filter, even though it cleans air for your central heating system. Let's dive into how often to change it and why it matters.

Key Takeaways 

  • Furnace filters play a crucial role in maintaining indoor air quality and ensuring the efficient operation of the furnace. 
  • Signs of a clogged filter include reduced airflow, increased energy bills, and a dirty appearance, indicating the need for replacement. 
  • Factors like the type of filter, air quality in the area, presence of pets, and household size determine the ideal frequency of filter changes. 
  • Regularly changing furnace filters is a simple yet effective way to improve energy efficiency, prolong the furnace's lifespan, and enhance indoor air quality. 

How Often Should You Change Your Furnace Filter - Image of an infographic on Custom Size Air Filters.

First, What Does a Furnace Filter Do?

Why is a furnace filter important? It acts like a shield, trapping dust and debris before they clog your furnace and HVAC system. This keeps your equipment running smoothly, improves indoor air quality, and even saves you money on heating and cooling costs

Other benefits come from using furnace filters. In addition to keeping the HVAC system clear of contaminants, furnace filters also help clean the indoor air that you breathe. All the air purification allows the HVAC system to run as efficiently as possible, which lowers the cost of heating and cooling a home. Learn more about different types of furnace filters.

How Often to Replace & Change Your Furnace Filter

Your specific situation is unique, but most air filtration experts agree that there is a general lifespan for furnace filters.

The standard recommendation is to replace furnace filters at least once every 90 days.

Keep in mind, this is a general recommendation. There are a few factors that can shorten or extend the time between furnace filter replacement intervals.

Furnace Filter Thickness & Change Intervals

One of the biggest variables is the thickness of your furnace’s filter.

Furnace filters are typically 1-, 2-, 4- and 5-inches thick. The thicker a furnace filter is, the more it can hold and the longer it will last. Below is a quick reference for filter thickness and change intervals:

  • 1” furnace filters should be replaced every 1-3 months.
  • 2” furnace filters should be replaced every 1-3 months.
  • 4” furnace filters should be replaced every 6-9 months.
  • 5” furnace filters should be replaced every 9-12 months.

The thickness of your furnace filter is dictated by your air handler and furnace’s filter slot. You can’t try to cram a larger air filter in a small vent slot. It’s also not advised to use a furnace filter that is too thin for your furnace filter slot. That will result in inadequate filtration and contaminants making their way into the air in your home.

Also keep in mind that thicker furnace filters tend to last longer, providing more filtration over time, so they tend to cost more than 1” and 2” furnace filters.

How Often Should You Change Your Furnace Filter - Image of various types of Air Filters in Various Sizes and MERV Rating.

Not All Central Air Systems Have a Furnace Filter

You may not have realized your furnace filter needs to be changed because furnace filters aren’t needed in every HVAC system. It all depends on the equipment that’s involved and how the system is designed. Below are a few instances when an HVAC system won’t need a furnace filter.

Central Air Systems Without a Heating Component

Some people live in climates where air cooling is needed almost year-round, which means heating the house isn’t a concern. HVAC systems can have no heating component and therefore they don’t need a furnace filter.

HVACs With Single Air Filtration Systems

Some HVACs are designed to have a single air filtration system rather than a separate system for the air conditioner and furnace. When this is the case just a single HVAC air filter is needed. The filter is placed in a shared air handler where it cleans the air before it’s diverted to either the conditioning unit or furnace.

Signs It's Time to Replace Your Furnace Filter

There are a lot of variables that influence how often a furnace filter needs to be changed. Plus, you may need to change the furnace filter more frequently at certain times of year. Instead of just going off the standard timeline, below are some signs and special considerations that will let you know when to change a furnace filter.

Symptoms of an Old or Dirty Furnace Filter

  • Increased heating bills and energy costs during colder months
  • Worsened air quality inside the house
  • Constant temperature fluctuation
  • The furnace shuts down due to clogs in the equipment
  • The heat exchanger is prematurely worn or damaged
  • The presence of dust and pet dander around the house
  • Increase in allergies breathing issues or symptoms

When in doubt, just take a quick look at your furnace filter. When a filter has reached the end of its life it will appear very dirty. Instead of seeing white pleats, the air filter medium will be a darker color, often grey or brown. You may even see larger bits of debris.

How Often Should You Change Your Furnace Filter - Image of a Dirty Air Filter after it was removed from the HVAC.

Furnace Filter Change Intervals in Winter vs. Summer Months

Winter: You might be able to stretch filter changes to the recommended 3 months (or 90 days) during winter, as long as the filter looks clean. But heavy furnace use during cold snaps can clog it faster, so check it monthly.
Summer: Your air conditioner runs more in summer, pulling more air (and dirt) through the filter. Change it monthly to avoid clogs, especially with high humidity.

Remember, these are general guidelines. The best way to know for sure is to inspect your filter monthly and replace it when it looks dirty.

What Could Happen If You Don’t Change Your Furnace Filter

Yikes! What happens if I forget to change the filter?

You might think skipping a filter change isn't a big deal, especially if you have good air quality. But even in mild climates, a clogged filter can wreak havoc on your furnace. Here's why:

  • Strained System: The filter protects your furnace from dust and debris. A clogged filter forces your furnace to work harder, leading to inefficiency and potential breakdowns.
  • Shorter Lifespan: Think of your filter as a shield for your furnace. Without it, dirt builds up inside, shortening the lifespan of your entire HVAC system.
  • Higher Bills: A struggling furnace uses more energy to heat your home, which translates to higher utility bills.

Regular filter changes are a small price to pay for a healthy and efficient HVAC system.

Shop Furnace Filters

Looking for the best air filters for your home? At Filterbuy you can find specialty furnace filters and standard HVAC filters in a wide range of sizes and thicknesses. We can also create custom-size furnace filters so you get an exact fit!

We also offer 5-inch furnace filters (16x25x5 or 20x25x5), whole-house air filter brands, and rigid cell furnace filters.

Furnace Filter Changing FAQs

How often should you replace your furnace filter?

The general recommendation is that furnace filters should be replaced at least once every 90 days.

How long is a furnace filter good?

A furnace filter will last if the medium can collect airborne contaminants. Once the medium is fully saturated it will no longer be able to filter the air.

How often should you change a 1-inch furnace filter?

A 1-inch furnace filter should be changed at least once every 1 to 3 months or every 90 days.

How often should you change a 2-inch furnace filter?

A 2-inch furnace filter needs to be changed every 1-3 months.

How often should you change a 4-inch furnace filter?

A 4-inch furnace filter should be changed sometime between six and nine months.

How often should you change a 5-inch furnace filter?

You can wait 9 to 12 months before needing to replace a 5-in furnace filter.

How often should you change a furnace filter in the winter months?

During the winter when the furnace is used more often, you will need to replace the furnace filter more frequently. It’s not uncommon for furnace filters to need to be replaced once a month in the winter. However, if your HVAC has a single filtration system that uses one air filter for the conditioning unit and furnace then replacements will be less frequent in the winter compared to the summer.

How often should you change a Honeywell furnace filter?

A Honeywell furnace filter is going to have the same filter replacement recommendations as standard filters. Just be careful not to confuse Honeywell furnace filters with their HEPA air filters for purifiers, which last much longer.

How often should you change a Carrier furnace filter?

A Carrier furnace filter has similar filter replacement recommendations. Carrier’s fiberglass furnace filters should be changed every 30 days. Their pleated furnace filters can last anywhere from 3 months up to a year.

How often should you change an Aprilaire furnace filter?

Aprilaire furnace filters tend to last a little longer than the norm. The manufacturer recommends changing their filters every 6 to 12 months.

How often should you change an Air Bear furnace filter?

Some Air Bear furnace filters can last six to nine months before needing to be replaced.

Do you need to change the furnace filter every 3 months?

Yes, it is generally recommended to change your furnace filter every 3 months. Regularly changing the filter helps maintain good indoor air quality, reduces strain on your HVAC system, and can help lower energy bills.

How Can I Tell if My Furnace Filter Needs Changing?

You can tell if your furnace filter needs changing by removing it and holding it up against a light source. If the light is fully blocked by the filter, it's likely too dirty and needs replacement. Another sign that your furnace filter needs changing is when your furnace starts running constantly but your home isn't getting any warmer.

Do You Need to Change the Furnace Filter Every 3 Months?

The standard recommendation is to change your furnace filter every 1-3 months, depending on the type of filter you have and the conditions within your home. For instance, if you have pets or if someone in your household has allergies, you may need to change the filter more frequently to ensure optimal air quality.

How Often Should You Change Your Furnace Filter in the Winter?

During the winter, your furnace is likely running more frequently to keep your home warm. This means more air is being circulated and your filter is catching more particles. Because of this, it's recommended to check your filter at least once a month during the winter and replace it if necessary.

How Long Should Furnace Filter Last?

The lifespan of a furnace filter can vary greatly depending on the type of filter, how often your furnace runs, and the air quality in your home. However, most filters should be changed every 1-3 months for optimal performance.

What Happens if You Don't Change Furnace Filter?

If you don't change your furnace filter, it can become clogged with dust and other particles. This can cause your furnace to work harder to circulate air, leading to increased energy consumption and potentially damaging your furnace. Additionally, a dirty filter won't be as effective at improving air quality, which can lead to health issues.

How to Tell if an Air Filter Is Dirty?

To tell if an air filter is dirty, remove it and hold it up to a light source. If the light can't pass through, the filter is likely too dirty and needs to be replaced. Another sign is an increase in dust around your home.

Can I Change My Furnace Filter Once a Year?

While you technically can change your furnace filter only once a year, it isn't recommended for most households. Most filters need to be changed every 1-3 months for optimal performance. Failing to change your filter regularly can lead to increased energy consumption, decreased air quality, and potential damage to your furnace.

What Happens if You Leave Your Furnace Filter in Too Long?

If you leave your furnace filter in for too long, it can become clogged and make your furnace work harder to circulate air. This can lead to increased energy consumption and can potentially damage your furnace. Additionally, a dirty filter won't be as effective at improving air quality.

How Many AC Filters Are in a House?

The number of AC filters in a house can vary based on the size of the house and the number of HVAC units. However, most homes have at least one filter per HVAC unit. Larger homes or homes with multiple units may have more.

Does Changing Filter Improve Heat?

Yes, changing your furnace filter can improve the efficiency of your heating system. A clean filter allows air to flow more freely, reducing the amount of work your furnace has to do to circulate warm air. This can lead to more effective heating and lower energy consumption.

Why Does My Furnace Filter Get Dirty So Fast?

Your furnace filter might be getting dirty quickly because of factors like having pets, smoking indoors, or having a large number of people in the house. It could also indicate that your home has high levels of dust or other airborne particles.

How Long Can You Go without Changing Air Filter?

The maximum length of time you should go without changing your air filter is typically three months. However, this can vary based on factors such as the type of filter you use, the air quality in your home, and how often your HVAC system is running. In general, it's a good idea to check your filter once a month and replace it if it's dirty.