The spreadsheet (pet household, MERV 11 16×25×1)
Assumptions: 5 changes/year (72-day interval), Amazon list prices May 2026.
| Purchase style | Annual filters | Approx. annual cost |
|---|---|---|
| 30-day auto-ship (12 boxes) | 12 | $216–264 |
| 60-day auto-ship (6 boxes) | 6 | $108–132 (often still early) |
| 6-pack bulk, buy twice | 10–12 on hand, 5 used | $95–125 |
| Big-box 2-pack × 3 trips | 6 | $78–102 (if you actually need 5) |
When subscriptions are fine
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- Vacation home you visit quarterly — set-and-forget
- Landlord supplies filters to tenants on a fixed schedule
- You truly change exactly on the ship date (rare with pets)
When bulk wins
- You already log pressure or visual loading
- Pets or pollen shorten cycles unpredictably
- You have closet space for a six-pack
Fridge filters — different trap
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Fridge cartridges often push 6-month subs while light-use homes run 9 months. Buying a two-pack when taste changes beats annual subs that ship winter filters you stack in a drawer.
Action step
- Count changes you made last year (honest count).
- Compare to ship frequency on your sub account.
- Switch to bulk for HVAC; keep one spare fridge cartridge on shelf.
Calendar: Replacement calendar.
