Filter Cost-Per-Year Comparison Method
Compare filters on annualized cost, not sticker price: (filter price ÷ months of life) × 12. A cheap-looking filter replaced every 3 months can cost far more per year than a pricier filter that lasts 12 months — sticker price alone actively misleads the comparison.
The one thing to know: The purifier itself is often the cheap part; the filter is the recurring cost — sometimes called the 'razor and blades' model. A True HEPA cartridge typically runs every 6-12 months depending on use and air quality, and combined HEPA+carbon cartridges cost more per swap than a HEPA-only filter since you're replacing fresh carbon media whether or not it's saturated. Comparing purifiers on sticker price alone hides this: the true cost is (filter price ÷ months of life) × 12, and it can vary several-fold between models with similar CADR.
The method, step by step
- Find the specific replacement filter's price band and its manufacturer-rated life in months (not just "up to X months" marketing — use the realistic average for normal household use).
- Divide price by months of life, then multiply by 12 to get the annualized cost.
- If the purifier uses a bonded HEPA+carbon cartridge, use the combined price and life — don't split them, since you replace both together regardless of which saturates first.
- Compare that single annualized number across every model you're considering, independent of the purifier's own upfront price.
Worked example
| Filter | Price band | Rated life | Annualized cost |
|---|---|---|---|
| Budget HEPA-only cartridge | ~$20-25 | 6 months | ~$40-50/year |
| Mid HEPA+carbon combo | ~$35-45 | 8 months | ~$53-68/year |
| Long-life HEPA+carbon combo | ~$45-60 | 12 months | ~$45-60/year |
These are illustrative price bands for comparison, not a quote for any specific product — always check the current listing before buying.
Common replacement filters
Research-based reference (how we evaluate), not hands-on lab tests. Live Amazon search links, no prices or ratings, an honest note on each.
LEVOIT Core 300 True HEPA Replacement Filter
Fits Core 300/300S; True HEPA + activated carbon combo, ~6-8 month typical life at normal use
A combined HEPA+carbon cartridge sized specifically for the Core 300 line, on a roughly twice-a-year cadence.
Best for: Keeping a Core 300 at rated CADR performance
Watch out: Cheap-looking off-brand 'compatible' filters flood Amazon search results; the genuine LEVOIT-branded cartridge is the only one verified to the original CADR rating.
Check current listing on AmazonHoneywell HPA300 Filter Q Replacement
Fits HPA200/HPA300; True HEPA, ~12 month typical life, separate pre-filter changed more often
A long single-cartridge interval (about a year) versus units needing quarterly changes, evening out the true annual filter cost.
Best for: HPA300 owners on a once-a-year replacement schedule
Watch out: The carbon pre-filter wrap around the HEPA filter saturates with odor faster than the HEPA media itself degrades, so heavy-odor households may want to replace it more often than the 12-month HEPA interval suggests.
Check current listing on AmazonCoway Airmega 400 Max2 Replacement Filter
Fits Airmega 400/400S; combined HEPA + activated carbon, ~12 month typical life
A single combined cartridge simplifies replacement (one part number, one order) versus multi-stage systems with several separate filters to track.
Best for: Airmega 400 owners wanting a once-a-year single-cartridge routine
Watch out: Because carbon and HEPA are bonded into one cartridge, you replace (and pay for) fresh carbon media every time even if only the HEPA layer has actually reached its dust capacity.
Check current listing on AmazonFrequently Asked Questions
(Filter price ÷ filter life in months) × 12. This normalizes filters with different replacement intervals onto a single yearly-cost basis so you can compare them fairly regardless of sticker price.
A $25 filter replaced every 3 months costs $100/year; a $40 filter replaced every 12 months costs $40/year. Comparing sticker prices alone would wrongly suggest the $25 filter is the cheaper choice.
Not reliably — a cheaper purifier can have a pricier or shorter-lived proprietary filter than a pricier purifier with a longer-lasting or more widely available cartridge. Always check the specific replacement filter's price and rated life separately from the machine's price.
Yes — a combined cartridge is typically priced and rated as one part, so its 'life' figure covers both media together. If your household has heavy odor needs, the carbon portion may effectively saturate before the HEPA portion needs replacing, meaning you're paying for the full combined cartridge more often than the HEPA media alone would require.
Manufacturer subscription or multi-pack pricing can lower the per-filter cost, but always recompute the annualized figure using the discounted price and the same life-in-months denominator — a bulk discount on an already-expensive-per-year filter can still land worse than a modestly priced filter with a longer life.