How often should you change your HVAC filter?
Updated July 2026
Change a standard 1-inch pleated HVAC filter every 90 days — and move to every 30–60 days if you have shedding pets, allergies, or the system runs constantly in peak season. Cheap 1-inch fiberglass panels only last about 30 days, while thick 4–5-inch media filters genuinely go 6–12 months. The right answer is your filter type first, then your household — the table below covers both.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| 1" fiberglass (the $2 panel) | Every 30 days | Low surface area loads up fast; it protects the equipment, not your air |
| 1" pleated, MERV 8 (the default) | Every 90 days | The manufacturer baseline for an average home, two people, no pets |
| One shedding pet | Every 60 days | Fur and dander load the pleats roughly a month faster |
| Multiple pets, allergies, or smokers | Every 30–45 days | Higher-MERV filters catch more, so they clog sooner |
| Peak summer / winter (system running daily) | Check monthly | Runtime, not calendar time, is what loads a filter |
| 4–5" media filter (in a filter cabinet) | Every 6–12 months | 5–8× the pleat surface of a 1" filter |
| Vacation home / mild seasons | Every 6 months | A system that barely runs barely loads its filter |
The cost of skipping it
What skipping it costs: a clogged filter makes the blower work harder — the U.S. Department of Energy puts the energy penalty of a dirty filter at 5–15%. Starved airflow also freezes AC evaporator coils in summer (a $200–600 service call) and overheats furnace heat exchangers in winter — cracked exchangers run $1,500+ and are a carbon-monoxide risk. A year of filters costs $20–60. It is the single highest-leverage habit in home maintenance.
How to do it (10 minutes · DIY, no tools)
- Turn the system off at the thermostat.
- Find the filter: in the return-air grille on a wall/ceiling, or in the slot where the return duct meets the furnace/air handler.
- Slide the old filter out and note the size printed on the frame (e.g. 16×25×1) and the airflow-arrow direction.
- Insert the new filter with the arrow pointing toward the furnace/blower (with the airflow, not against it).
- Write the date on the filter frame with a marker, and turn the system back on.
Knowing the interval is the easy half. OnOtto reminds you at the right interval — and won't let you snooze it into next year. Tasks persist until they're done, and completing HVAC filter changes schedules the next one automatically.
Put this on autopilot — free for 30 daysFrequently asked questions
Can I run a higher-MERV filter for better air quality?
Usually yes up to MERV 11–13 in a modern system, but two caveats: higher-MERV 1-inch filters clog faster (change every 30–60 days, not 90), and very old or undersized systems can struggle with the added resistance. If you want MERV 13+ filtration long-term, a 4–5-inch media cabinet is the better upgrade — more surface area, less pressure drop, and 6–12-month changes.
Do washable/reusable HVAC filters make sense?
They save money but most washable electrostatic filters sit around MERV 4–8, must dry completely before reinstalling (damp filters grow mold), and need washing monthly. For most homes a pleated MERV 8–11 disposable changed on schedule filters better for less hassle.
My filter still looks clean at 90 days — should I change it anyway?
Hold it up to a light: if you can't see light through it evenly, change it. If it genuinely passes light and your system ran little that season, you can stretch a few more weeks. What you can't judge by eye is fine-particle loading on higher-MERV filters — when in doubt, the $5 filter loses to the $500 repair.
Does the filter schedule change between heating and cooling season?
The interval follows runtime, not the season itself. In a climate where the system runs hard all summer and all winter, check monthly in both and expect to change every 30–60 days; in mild shoulder seasons a filter barely loads. A good rhythm: change at the start of each heavy season, then check monthly during it.