Different sizes of air filters need to get changed at varying intervals of time. If the air filters of your air conditioner are 1-2 inches, change them every three months. If the air filters are 3-4 inches, change them once every six months, and if the air filters are 1-2 inches, you can change them once in a year. The frequency of changing your air filters also depends on how many members are there in your house and if your home has pets.