How Often Should You Change Your Furnace Filter?

Learn how often you should change your furnace filter and why it's important for HVAC maintenance. Find out what factors affect how often you need to replace your furnace filter.

How Often Should You Change Your Furnace Filter?

When it comes to taking care of your HVAC system, one of the most important things you can do is to change your air filter on a regular basis. The general consensus among HVAC professionals is that you should replace your furnace filter every 90 days or three months. However, this depends on the thickness of the filter and other factors such as the size of your home, the amount of dust in the air, and whether you have pets. Thinner filters need to be changed more often, while thicker filters can last up to a year.

For example, filters that are less than 2 inches thick should be replaced every 30 to 90 days, while 3- or 4-inch filters can last 6 to 9 months. Filters up to 6 inches thick can be replaced once a year. In spring and autumn, when there is less need for heating and cooling, the filter usually doesn't get as dirty so you can get by without changing it as often. And in a home that doesn't have a lot of infiltration or leaks in the ducts and a low level of dust in general, the filter can stay clean longer, even when used a lot (unless the return vents are on the floor).

Using an air filter with a MERV rating higher than recommended by the manufacturer of your furnace or air conditioner may impair its performance. If you live in a “smaller house”, your air conditioners and furnaces need to pump less air for the same amount of temperature change, which could mean fewer filter changes. For allergy sufferers, it is recommended to change the furnace filter every 30 to 60 days. If you have pets, you should also change the filter more often as pet hair and dander can clog up the filter quickly.

A clogged filter will make your furnace work harder to pump air through it, which will increase your energy bills and shorten the life of the furnace. We offer 5-inch furnace filters (16x25x5 or 20x25x), whole-house air filter brands, and filters for rigid cell furnaces. No matter how long you delay changing the filter, you should never detect a measurable increase in static pressure. So make sure to check your furnace filter regularly and replace it when necessary.