How Often Should I Change My HVAC Filter?

The most forgot about and simplest fix to a malfunctioning HVAC system is to replace the air filters. Many times all your HVAC system really needs is a new filter.

Before we talk about when you should replace your air filters, let’s first talk a little bit about what the air filter does for the HVAC system. The air filter is there to make sure mold spores, pet dander, dust, smoke, and pollen aren’t in the outside air when it gets to the furnace or cooling unit. This keeps the important components of your HVAC system clean and running more efficiently. Using your HVAC with an old filter can damage your HVAC system, allow dirty air flow through your house, and decrease the efficiency of your system.

Another good thing to know is that there are a few different types of filters with varying quality and sizes. Generally, the better the quality of the filter and the thicker the filter, the longer it can go without being replaced. Most filters’ sizes can vary from 1 to 6 inches thick. The highest quality filter is going to be a HEPA filter. A HEPA filter can filter out 99.7% of particles in the air that are 0.3 microns or larger. The next highest quality is going to be the electro static filter which uses electric charge to capture particles in the air. These filters can usually be washed instead of having to be fully replaced when dirty. Then there are pleated filters, which use its pleats to capture airborne particles. Lastly, there are cheap disposable fiberglass or synthetic filters that are good at capturing large particles in the air. All of these filters have their own benefits and drawbacks, so finding the right one for you is up to your preference.

Now lets talk about when you should change you filter based on which filter type your system uses. If you don’t know your filter type you can check it yourself, which I’ll talk about how to do later on, or you can call the HVAC specialist that installed your system or replaced the filter last. Fiberglass and synthetic filters on the thinner side should be replaced every moth or so and the thicker ones can last up to a couple months. The pleated filters should be changed about every 90 days. As for electrostatic filters, these can be washed as often as recommended by the manufacturer and can save you a lot of money in the long run. If your system uses HEPA filters, they should be replaced every 6 months to 1 year. Whichever filter your system may use, be sure to check it once a month to make sure it’s in good enough condition to use. If you can’t see light through it, then it’s definitely needs to be replaced.

This is a good general guide for when to replace your filter, but there are many other factors that can change how often you should replace your filter. Factors such as how often you use your HVAC system, the size of your home, and the quality of the air outside your home all change how long you filter will last. The more you use your system, the bigger the area your system covers, and the worse the outside air is the quicker you are going to need to replace your filter, which is why it is highly recommended to check your filter once a month. There are also other factors that can effect when you should change your filter, but on more of a set schedule. If you have asthma or allergy sufferers, then your filters should be changed every 6 weeks to make sure the level of allergens in your home stays low. If you have pets, your filters should be changed every 2 months or so. If you have young children, it is also recommended that your filters be replaced every 2 to three months.

How to safely find and check your HVAC filter. The first thing you need to do is to turn off your thermostat so your system isn’t running. Once your system is off, you can go to your filter access door and take out your filter. The filter access door is most likely going to be in your return air duct next to the furnace or indoor unit. Most filter access doors are in places like utility closets, basements, attics, or crawl spaces, so keep that in mind when searching. However, in older units the access door could be next to the blower motor in your HVAC system. Once you find your filter and take it out, you can hold it up to a light to check to see if the light shines through the filter, if it doesn’t then the filter needs to be replaced or washed.

Thanks for reading! If you want to learn more, here’s all the sources that were used to gather information: