A typical 1- to 3-inch air conditioner filter should be replaced every two months, according to Service Experts. If the air conditioner is in a seldom-used home, or if the home is occupied by one person with no pets, then the filter should be replaced every six to 12 months.
The original equipment manufacturer often specifies how often to change an air conditioner's air filter, but these specifications can be modified according to circumstances. The filter of an air conditioner in a suburban home should be changed every 90 days. If the same home has multiple pets or residents with allergies, then the filter should be replaced every 30 to 45 days.