How often should you replace your AC air filter?

Skipping it eventually leads to water damage or an expensive repair.

Staying on schedule matters beyond the repair bill: a consistent maintenance record is one of the factors in a home's Roots Home Health Score, and well-kept homes typically sell faster and closer to asking price.

How to do it

If your AC draws through its own filter separate from the furnace, the same rule applies: a clogged filter starves airflow, freezes the coil, and strains the blower.

1. Find the filter at the return grille or the air handler cabinet.
2. Read the size off the old frame and buy a pleated filter to match, MERV 8–11.
3. Insert it with the airflow arrow pointing toward the unit, and date the frame.
4. Check it monthly through cooling season and swap when it looks gray.

Alternatives & optional extras

• If your AC and furnace share one filter, that single filter covers both; don't hunt for a second.
• Skip this task entirely if your system has only the furnace filter.

Time: 5 minutes · Typical cost: $5–$25 per filter

What you'll need

• Pleated furnace/AC filter, MERV 8–11

If you skip it

A starved AC filter drops airflow until the evaporator coil freezes into ice and the system stops cooling.

Other air conditioner maintenance

• Schedule AC tune-up — once a year, ideally in April
• Flush AC condensate drain line — every 6 months
• Clear 2 ft around outdoor AC unit — once a year, ideally in May

Related systems to keep on schedule

• Boiler / radiators — start with: schedule boiler service, once a year, ideally in September
• Furnace / heating system — start with: replace hvac air filter, every 3 months
• Mini-split / ductless AC — start with: clean mini-split filters, once a month
• Tankless water heater — start with: descale tankless water heater, once a year