The general recommendation for changing HVAC filters is every 90 days (3 months). However, several factors can influence how often to change the filter:

• Standard 1-inch filters should be changed at least every 90 days.
• If there is high system usage, pets, allergies, or respiratory conditions, changing the filter every 30 to 60 days is advised.
• Homes with multiple pets or people with allergies may need to change filters every 20 to 45 days.
• Thicker or higher-efficiency filters may last longer, such as 6 months or more, but should be checked regularly.
• Signs that a filter needs changing include visible dirtiness, increased dust in the home, sneezing or allergy symptoms, higher energy bills, or reduced HVAC performance.

It is also recommended to inspect the filter monthly to determine if it needs earlier replacement, especially during heavy use seasons like summer or winter.