How Often to Change Air Filters

Here are all the clues indicating that it’s time for a swap.

Air filters can be found in several places in your home. They’re generally installed in air-conditioners, ventilation, furnace or other heating systems. There, they work to improve the air quality inside your living space.

Homes can be time-consuming to maintain, and filters tend to be left out and often forgotten. How often to change your air filter depends on various factors. But first, what exactly happens if you decide to skip changing your air filters?

Why Should You Change Air Filters?

An HVAC system pushes air through the filter, trapping dirt, dust, pollen, mold and other particles. When left unattended, filters accumulate dirt, and the following can occur:

  • Decreased airflow efficiency.
  • Damage to your cooling or heating equipment.
  • Lower air quality leading to cardiovascular and respiratory health complications and diseases (1).
  • A higher energy bill. Dirty filters make your HVAC system work harder, increasing your energy bill. For instance, unclogging your A/C can lower your electricity bill by 5 to 15 percent (2).

How Often to Change Air Filter?

If you live alone, don’t suffer from allergies or have young children and pets, switching your screen every six months is generally enough. Durability, however, depends on the type of filter you have. The better the quality, the more efficient it is at retaining dirt, and the longer it lasts.

Filter Types

Filter quality is based on the material used and MERV level — Minimum Efficiency Reporting Value (3).

The higher the MERV value is, the least amount of particles the filter lets through. For the best filtration, a screen with MERV 8 or higher is recommended (4).

1. Washable Filters

These filters are built with a thread-like mesh. Although they’re reusable, they provide the least amount of filtration — MERV 1 to 3. They’ll stop pollen, hair, dust and fur, but will let viruses, dust mites, smoke and spores go through.

These filters should be changed monthly or at least every three months.

2. Fiberglass Filters

Fiberglass filters are inexpensive and generally feature MERV levels from 2 to 4. Unlike washable screens, however, they are able to trap dust mites. Nonetheless, this type of screen should also be changed every 30 days to three months.

3. Pleated Filters

These are pricier options than the previous two. They can also capture more dirt than the two previous other types — MERV 6 to 10. Although some high-quality pleated filters can be replaced only every six months, a regular one should be swapped every 90 days.

4. Electronic Filters

These screens are electro-magnetically charged to provide a higher efficiency — MERV 8 to 16. Compared to other models, they can also stop viruses and smoke. Available at a higher price point, they require the use of specific HVAC systems.

These filters only need to be replaced once a year. This makes them a popular option for anyone with limited time to dedicate to filter maintenance.

5. HEPA Filters

Finally, HEPA filters are the high-end spectrum of air filters — MERV 17 to 20, filtering up to 99.9 percent of all particles (5). They can be costly but only need to be replaced every six months to a year. Some pleated models can even last up to two years (6).

Filter Thickness

Screens also come in various thicknesses, typically from 1 to 5 inches. The thicker the material, the more dirt it can hold, and the more durable it is.

Thickness Durability
1 inch Up to three months
2 inches Up to four months
4 inches Six to eight months
5 inches Up to a year

Special Conditions

In the following circumstances, you might want to replace the screen more regularly:

  • Allergy and asthma: If anyone in the family suffers from these conditions, it’s best to change it every month or up to six weeks.
  • Pets: Dogs and cats emit strong smells and shed hair between seasons. If you own one pet, replacing your filter every two months should be enough. But when several pets live inside a home, changing the air filter monthly is recommended.
  • Children: Babies and toddlers are sensitive to air quality. So switch out your air filter at least every two to three months to ensure they breathe clean air.
  • Heavy use: If you’re constantly using an A/C or a heating system, interchange them every few weeks as needed. On the other hand, if it’s your secondary home, checking it every six months should suffice.
  • Home size: The larger your home, the more air goes through, which may require more frequent maintenance.
  • Outdoor air quality: It’s also important to consider the quality of the air outside your home. If you live in a highly polluted area or near a highway, we recommend checking the filter condition more often.
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Indications Your Filter Needs Replacing

Not sure which of the categories above best describe your air filter? A quick visual check can give you a hint as to whether or not the screen should be changed.

If there is only a thin layer of dust, you can wait a few more weeks before changing it. But if you can’t see through it when holding the filter up to a light source, it’s time for a replacement.

In addition, if your electricity bill is higher than usual, that’s a sign to change. Or if you’re starting to feel the first signs of allergies, have a look at your screen’s condition.

How to Change an Air Filter

Changing an air filter is a simple and straightforward process.

User’s Manual

Starting by consulting the user’s manual is often a good idea. It gives you an indication of what type of filter is required and the size suitable for your HVAC system.

Bear in mind that replacing the filter with one not recommended by the manufacturer will likely void your warranty.

Type of Filter

Your second step will be to select the type of filter you need — washable, fiberglass, pleated, electronic or HEPA. Then, check the dimensions of your current screen to ensure the new one will fit.

Switch Filters

Before starting any work, turn off the HVAC system. Every piece of ventilation, cooling or heating equipment may come with a different opening system. But typically, you can access the filter by pulling a cover or unscrewing it; either way, it isn’t complicated.

Remove the old screen and place your new filter. On the side of the frame, you’ll notice arrows pointing in one direction — where the air is flowing. Ensure that the new screen is installed with the right orientation.

If you opted for a washable filter, spray the side opposite to the airflow. Keep the water pressure low to prevent the fiber material from breaking or separating.

Take a Deep Breath

Replacing your HVAC filter regularly is key to maintaining good quality air inside your home. Typically, the more particles your screen can stop, the longer it’ll last. A filter’s efficiency can be measured in MARV levels, generally ranging from 1 to 20.

Most models should be changed at least every six months. Yet, the filter’s quality, allergies or the presence of children and pets may require more frequent maintenance.

After selecting the size and type of filter you need, remove the old filter and place the new one in the right direction. It might be a good idea to write down your last maintenance date to schedule when the next one should be.

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About the Author

Matthew Sullivan

Matthew is a freelance writer with several years of experience in DIY and HVAC. For as long as he can remember, Matthew has always found great pleasure in taking things apart and learning how to put them back together.