In general, most air filters and HVAC companies recommend changing your air filter every 90 days or 3 months. This may vary depending on the location of your home, if you have pets, and the age of your system and equipment. The ideal is to change your air filter every three months, however, there are certain factors to consider when determining when to replace an old filter. The only way to ensure how often you need to change your air filter is to perform a visual inspection of the filter every month.
After a few months, you'll get an idea of how quickly it gets dirty. You will need to re-evaluate if you have a new pet or if the outdoor air quality has been poor. As a general rule of thumb for pleated air filters (such as those manufactured by FilterBuy), it is recommended to replace the filter every 90 days. As the filter traps more dirt, dust and allergens from the air, the efficiency of the filter decreases.
To determine if you should replace the filter more often, consider the following factors. If you have an electronic media filter, you don't need to worry about replacing the filter every 1-3 months. You can wait 6 months to a year before replacing it. However, you must replace it with the exact filter of the model.
This may require ordering it on the brand's website to get an exact match. The most important factor is how often your system is running. The filter collects dust and debris only when the system is operating. The more it works, the faster the filter picks up dirt.
During a cold winter or hot summer, a furnace filter will need to be changed more often than during milder seasons. Additionally, pet hair can clog up filters quickly due to its larger size compared to dust and dirt particles. The more important clean air is, the more often the filter needs to be cleaned or changed. A coarse-media filter, MERV 11 or higher, or an electronic air filter is best for those with asthma, severe allergies, or difficulty breathing for any reason.
You may also want to consider an air cleaner for your system. Cheap fiberglass filters require less frequent replacement than pleated filters as they don't trap as much dirt and debris and don't clog up as quickly. Some of these filters can be cleaned with a nylon brush and placed back in the oven or air controller instead of replacing them; however, cleaning should be done outside or in a garage to keep dust and dirt out of your home. If removing dirt with a brush instead of replacing the media filter, be sure to change the filter after two or three cleanings as brush cleaning will not remove enough deeply embedded dirt and debris.
In larger homes, more air flows through the filter than in smaller houses so it will get dirty more quickly in a system that serves a large house. Continuous fan mode is another factor that affects how often you should change your air filter. There must be a setting in the thermostat such as Auto and Fan options. In automatic mode, the fan works only when the system is heating or conditioning the air in your home while in fan mode it works all the time until you turn it off.
The longer the system works, even if it is not heating or air conditioning, the faster the filter will get dirty and it will need to be changed. While running the fan requires electricity and can help balance temperatures in your home, it can also bring warm air from inside walls or attic which can cause your air conditioner to work more often resulting in higher electricity costs. To find out when to change your air filter, perform a visual inspection of it every month and consider all factors mentioned above such as location, pets, age of system and equipment, type of filter used etc. If you hear a little wheezing even when the filter is clean, it will worsen when the filter is dirty so make sure to replace it.