The short answer
- Costs $1,069 to own over five years: $390 to buy, $163 in electricity, $516 in filters.
- The filter bill is 48% of that. Four Max2 sets at $129, because the first one comes in the box.
- Coway claims 1,560 sq ft. That is at two air changes an hour. At the 4.8 changes an hour that allergy use calls for, the same CADR covers about 510 sq ft.
Who this is for
Buy the Airmega 400 for a room of up to about 510 square feet where you intend to keep it running, and where you have understood that the filters cost more over five years than a third of the machine. Do not buy it for the 1,560 square feet on the box: that number assumes two air changes an hour, which is a comfort standard, not an allergy one.
At the $389.99 Coway was asking on 31 August 2026, down from a $649.00 list price, it is a lot of verified airflow for the money. The figure that decides it is not the sticker price but the $129 filter set, due every twelve months.
What the specifications actually say
Coway publishes a CADR of 328 for smoke, 328 for dust and 400 for pollen, and describes them as AHAM Verifide figures. Smoke is the number that matters, because it is measured on the smallest particles of the three.
From that 328 you can derive the coverage two ways, and both land in the same place. AHAM’s own rule of thumb, CADR multiplied by 1.55, gives 508 square feet. Working from the airflow directly, 328 CFM in a room with eight-foot ceilings delivers 4.8 air changes an hour at 512 square feet. Call it 510. The manufacturer’s 1,560 square feet is the same machine measured against a much lower bar.
One number Coway does not publish is power draw by fan speed. The 66 W on the spec sheet is the maximum. Every electricity figure on this page uses that maximum, so the running cost below is a ceiling rather than a best guess — on auto or on low the real figure will be lower, and we would rather overstate a cost than invent a number Coway declines to supply.
| Specification | Value | Source |
|---|---|---|
| CADR (smoke) | 328 CFM | Coway spec page; AHAM Verifide figure as published by the manufacturer, retrieved 31 Aug 2026 |
| CADR (dust) | 328 CFM | Coway spec page, retrieved 31 Aug 2026 |
| CADR (pollen) | 400 CFM | Coway spec page, retrieved 31 Aug 2026 |
| Manufacturer coverage | 1,560 sq ft at 2 ACH | Coway spec page |
| Coverage at 4.8 ACH | 510 sq ft | Calculated from CADR 328 at an 8 ft ceiling |
| AHAM suggested room size | 508 sq ft | Calculated as CADR x 1.55, AHAM sizing guidance |
| Power draw (maximum) | 66 W | Coway spec page; no per-speed figures published |
| Filter life | 12 months | Coway Max2 filter page |
| Replacement filter set | $129.00 | Coway store, retrieved 31 Aug 2026 |
| Noise | 22-52 dB(A) | Coway spec page |
| Warranty | 1 year parts, 5 years motor and electronics | Coway warranty documentation |
| Price | $390 | Merchant listing at publication |
The cost nobody quotes
Five years, at the US average of $0.17 per kWh, running eight hours a day.
What it really costs over 5 years
Total$1,069
| Cost | Amount | How we got it |
|---|---|---|
| Purchase price | $390 | Street price at publication |
| Electricity | $163 | 192 kWh/yr at $0.17 per kWh |
| Filters & consumables | $516 | $103 per year |
| Total | $1,069 | $214 per year · $0.07 per session |
Running costs are 64% of the 5-year total. The sticker price is not the decision.
Electricity priced at $0.17 per kWh, the US residential average. Change the rate in the settings to match your utility. Consumable costs come from the manufacturer's published replacement schedule.
The filter line is the one to read twice. A Max2 set is $129 and lasts twelve months, and the machine ships with the first set fitted. Over five years that is four sets, $516, which we have averaged to $103 a year so the arithmetic above stays honest. It is 48% of everything you will spend, against 37% for the machine itself.
Electricity, by contrast, is almost a rounding error: 192 kWh a year at the maximum draw, $32.67 a year, $163 across the whole five years. Anyone choosing an air purifier on wattage is optimising the smallest of the three numbers.
Certifications, and what they cover
Frequently asked questions
How much does the Airmega 400 cost to run per year?
About $33 a year in electricity at the US average rate of $0.17 per kWh, running eight hours a day (66 W x 56 h/week x 52 = 192 kWh). That uses Coway’s maximum published draw, so it is an upper bound.
How often do the filters need replacing, and what do they cost?
A Max2 set lasts twelve months and costs $129 from Coway. The unit includes the first set, so expect four sets across five years, or $516.
What room size does it really cover?
About 510 square feet at 4.8 air changes an hour, calculated from the AHAM CADR of 328. Coway’s 1,560 square feet is measured at two air changes an hour.
Why do you not test these yourself?
We are a research publication, not a lab. We verify third-party test data, publish the source next to every number, and calculate the costs manufacturers leave out.
