How Often Should You Change Your Home's Furnace Filter?

Find out when to change a furnace air filter to keep the air in your home clean.

There are many tasks that need to be checked off your home maintenance list on a regular basis. Shoveling snow, mowing the lawn, and sweeping floors are just a few examples of basic home duties that help ensure your home is both functional and comfortable.

Another crucial home maintenance job that all homeowners should know about is changing the air filter in the furnace. Dust, dirt, hair, and other debris get trapped in the air filter. Over time, the filter can become clogged, restricting the flow of air through the filter and into the home. Not only does this reduce the air quality, but it also negatively impacts the efficiency of your heating and cooling system. Use this guide to learn more about air filters and find out how often you should change your home's air filter.

What Is an Air Filter?

There are two common types of home air filters, including spun fiberglass and pleated paper. The filters are designed to trap dust, dirt, pet hair, lint, mold, bacteria, and other contaminants.

By filtering these contaminants, a furnace's filter improves the air quality within a home, making it easier to breathe. This is especially important in homes with individuals that suffer from allergies or respiratory conditions.

The easiest way to find an air filter that is suitable for your home is to locate the filter that is already installed. Check the sides of the existing air filter to find the dimensions, then head online or to a local home improvement store to find an air filter that matches the listed dimensions.

removing a furnace filter

BanksPhotos / Getty Images

Understanding MERV Ratings

When shopping for a new air filter, make sure to check the MERV rating on the packaging. MERV is an acronym for minimum efficiency reporting value. This rating can be used to determine how effective a filter is at stopping dust and other contaminants. In general, filters with higher MERV ratings are more capable of trapping small particles than filters with lower MERV ratings.

Keep in mind that a higher rating does not necessarily mean that the air filter is the right choice for your home. If you install an air filter with a MERV rating higher than what the furnace or air conditioner manufacturer recommends, you could impair the performance of the heating and cooling system. In most cases, air filters with a MERV rating of 16 and below are intended for residential, commercial, and institutional HVAC systems. Air filters with MERV ratings that fall between 17 to 20 are intended for areas that require absolute sterility, such as operating rooms or rooms for immunocompromised individuals.

Side by side close up view of a new unused and an old heavily clogged dirty air filters
Grandbrothers/Adobe Stock

How Often Should You Change an Air Filter?

When an air filter has been in use for a long period of time, it gradually begins to restrict the air flow through the heating and cooling system. This reduces the efficiency of the system, leading to higher heating and cooling bills. If the filter remains unchanged, it can even shorten the life of the furnace or air conditioner, so it's important to include air filter replacement on your list of recurring home maintenance jobs.

When you purchase a new air filter, check the manufacturer's recommendations to get a basic idea of how frequently to change the filter. On average, you should change a fiberglass air filter about once every 30 days, while you can leave a pleated air filter for about three to six months before needing to replace it.

If you're installing the air filter in a vacation home, cottage, or other property that isn't commonly used, you can usually wait a bit longer to replace the filter. Wait up to three months to change a fiberglass air filter and nine to 12 months before changing a pleated air filter.

Just keep in mind that every home is different. What may be a suitable air filter replacement frequency for one home might not be the right choice for every home. To get a better understanding of when to replace an air filter, consider the size of the home, number of people, number of pets, and whether there is anyone that has severe allergies or that smokes inside the home.

Factors That Impact Air Filter Life

Typically, you should replace a fiberglass air filter about once every 30 days or as recommended by the manufacturer. A pleated air filter should be replaced about once every three to six months. However, the air filter replacement frequency depends on several important factors, including your home, the occupants, and its location.

On average, an air filter lasts longer in a small home than in a large home. This is because there is more air to filter through in a large home. Similarly, households with several people will require more frequent air filter replacements than a home with a single occupant. More people create more dust, dirt, hair, skin, and other debris.

Pets should also be factored into the replacement time frame. Dogs, cats, and other pets shed and leave dander around the home, reducing the life of an air filter. Consider replacing a fiberglass air filter about once every 20 days and replacing a pleated air filter about once every 60 days if you have one or more pets.

External factors, such as excess pollen, nearby construction, or a home renovation, can also shorten the life of an air filter. Generally, if you find that you need to vacuum or sweep more often than normal, it's likely that the air filter will also need to be replaced more frequently.

Signs an Air Filter Needs to Be Changed

If you have never changed an air filter, you might not be aware of these common signs that indicate it needs to be changed. If you notice that your heating and cooling bills are gradually increasing, it might be a sign that the efficiency of your system is starting to drop because the air filter needs to be replaced. Air filters are designed to allow air to flow freely through them while trapping dust, dirt, bacteria, and other contaminants. When neglected too long, the filter can start to restrict airflow, leading to higher heating and cooling costs. 

Another sign that a home's air filter needs to be changed is reduced airflow through the vents. When the filter becomes clogged with dirt and debris, the air cannot pass through the filter properly. This can also result in increased dust quantities throughout the home. If this is the case, you will likely notice that you are dusting more frequently and that the air quality seems to have diminished, making it harder for those with allergies or respiratory conditions.

Replace the air filter to restore airflow, improve heating and cooling efficiency, and increase the air quality throughout the home. If you change the air filter and these problems persist, it's recommended to contact a professional HVAC technician to help address the root of the issue.

Was this page helpful?
Related Articles