furnacefiltersize.com
How often to change a furnace filter.
Zero-click answer is “every 1–3 months.” The useful object is a matrix: thickness × pets × smoke. The table below is our synthesis of OEM ranges — not a new study.
What OEMs and EPA actually wrote
- Trane (Furnace Filters 101, 6 Nov 2025, Sean Goddard): most filters every 1–3 months, year-round. Cue: first of the month or first day of a new season. Pets or pollen: more often. The filter works whenever the system runs, including summer.
- Trane maintenance guide: plan on a standard 1-inch at least every 90 days; 30 days if high use, allergies, or pets. Thicker high-efficiency (Trane QuikBox) ~6 months.
- Carrier (how-often page, expert-reviewed by Michelle Notaro): 1-inch fiberglass every 30 days; 1-inch pleated 30–90 days; 4-inch media 6–12 months. Multiple pets: check every 30 days. Indoor smoking, candles, fireplaces, construction: at least every 30 days.
- EPA Guide: follow the manufacturer; many recommend 60–90 days; if the filter looks heavily soiled at change-out, shorten the interval. Check monthly is the This Old House reading of EPA (TOH, updated 9 Apr 2026, citing Trethewey 2–3 months).
- DOE Energy Saver: replacing/cleaning filters can cut AC energy use 5–15%. (DOE Home Cooling 101 PDF.) A reason-to-change, not a bill calculator.
- Aprilaire 213 official shop: 12-month replacement for that media cartridge. Do not apply 90-day 1-inch advice to a 213.
- Carrier EZ Flex: 6–12 months (Atomic Filters, citing Carrier). Infinity GAPCCCAR: ~12 months. Performance PGAPXCAR: 8–12 months. (Atomic Filters, July 2026 — first-party merchant; confirm against Carrier IOM before locking.)
Matrix (synthesis of the ranges above)
| Depth / type | Baseline | Pets or pollen | Indoor smoke / wildfire week |
|---|---|---|---|
| 1-inch fiberglass | 30 days (Carrier) | 30 days | 30 days or when gray |
| 1-inch pleated MERV 8–11 | 60–90 days (Trane/Carrier) | 30–60 days | 30 days |
| 1-inch pleated MERV 13 | 60–90 days if the blower accepted it | 30–60 days | 30 days; see 1-inch MERV 13 |
| 4-inch / 5-inch media | 6–12 months (Carrier) | 6 months | inspect after smoke |
Download a first-of-the-month reminder (.ics) — no email list in v1. Trane’s cue is the first of the month; the file repeats monthly. Shorten it yourself for pets, smoke, or 1-inch MERV 13.
Interval from the finder
Landlords with mixed cadences: one calendar, not a building-wide 90-day rule. Landlord page.
Affiliate: Filterbuy auto-delivery is their reminder product — we do not run a subscription. Amazon Subscribe & Save as backup for common 1-inch. We do not pitch Second Nature; they own large PM, not this job.