How Often Should You Change Your HVAC Filter?
Changing your HVAC filter is one of the easiest and most important things you can do for your heating and cooling system. A clean filter keeps your system running efficiently, improves your indoor air quality, and helps prevent costly repairs. But how often should you actually change it?
The General Rule
For most homes, you should check your filter every 30 days and replace it at least every 90 days (3 months). But the right schedule depends on your specific situation.
Change More Often If...
- You have pets. Pet hair and dander clog filters much faster. If you have one pet, check monthly and replace every 60 days. Multiple pets? Check every 2-3 weeks.
- Someone in your home has allergies or asthma. A fresh filter makes a real difference in air quality. Consider checking every 30 days.
- You run your system constantly. During peak summer and winter months when your system runs a lot, filters clog faster.
- You have a large family. More people means more dust, skin cells, and activity that generates particles.
- You're doing renovation work. Construction dust can clog a filter in days. Change it frequently during projects and right after they're done.
What Happens When You Don't Change It?
A dirty filter restricts airflow through your system. This causes several problems:
- Higher energy bills — your system has to work harder to push air through a clogged filter
- Uneven heating or cooling — reduced airflow means some rooms won't get enough conditioned air
- System damage — restricted airflow can cause your AC evaporator coil to freeze or your furnace to overheat and short-cycle
- Poor air quality — a saturated filter can't trap new particles, so they circulate through your home
Which Filter Should You Buy?
Filters are rated by MERV (Minimum Efficiency Reporting Value). A higher MERV number catches smaller particles. For most homes, a MERV 8-11 filter is the sweet spot — good filtration without restricting airflow too much.
Avoid the cheapest fiberglass filters (MERV 1-4) if possible — they barely catch anything. And unless your system is designed for it, skip the ultra-high MERV 13+ filters, as they can actually restrict airflow and stress your system.
Quick Tip: Set a Reminder
The easiest way to stay on top of filter changes is to set a recurring reminder on your phone. Pick the first of each month to check your filter. Hold it up to a light — if you can't see light through it, it's time for a new one.