Most experts advise that homeowners change standard 1″ air filters once a month when their A/C, heat pump or furnace is used on a daily basis. When you run your HVAC equipment intermittently, you may be able to extend that time frame to perhaps once every six weeks or every two to three months.
If you have family members with allergies or asthma you may want to change your air filter more often.
If you have pets in the home with dander or who shed, it’s desirable to change the filter frequently.
When you’re conducting home projects that create dust and dirt, during that period of time, you should keep your eye on the air filter, as it will become fuller faster.
There are Extended Life Air Filters that require changing less frequently and clean the air better than standard 1″ filters.