Research basis: Desk research conducted 2026-09-23 (public web: manufacturer, retailers, independent review/test sites) plus attributed owner evidence. No hands-on testing was performed — nothing here is a first-hand test result. Research date: 2026-09-23
At a glance
Coway's large-room dual-filter flagship (non-smart base 400; the 400S adds app). Two Max2 combined activated-carbon/HEPA filter units plus washable prefilters. Strong CADR for the price; no Wi-Fi/app on the base model.
Specifications
| Spec | Value | Basis |
|---|---|---|
| CADR | Smoke 328 CFM / dust 328 CFM / pollen 400 CFM | Manufacturer; reviews |
| Room coverage | 3,120 sq ft at 1 ACH; 1,560 at 2 ACH; ~624–780 at high ACH (methodology-dependent) | Manufacturer marketing + review conversions |
| Filter | Dual washable prefilters + 2× Max2 combined activated-carbon/HEPA; 6–12 months / ~1 year | cowaymega.com |
| Noise | 22–52 dBA | Manufacturer/reviews |
| Power | 66 W | Manufacturer |
| Smart features | None on base 400 (no Wi-Fi/app) — the 400S variant adds connectivity | Reviews |
| Warranty | Standard Coway terms — check listing (not verified this round) | UNVERIFIED |
Pricing & total cost of ownership (dated 2026-09-23)
| Item | Figure | Dated source |
|---|---|---|
| Unit price | $649 | cowaymega.com, observed 2026-09-23 |
| Max2 filter set (400/400S) | $129.00 (25% off first subscription) | cowaymega.com shop-all page, crawled 2026-09-23 |
| Annual filter cost | $129/yr (official set, ~annual) — but estimates conflict: owner-review estimates ~$80–90/yr; other sources ~$120–200/yr | Conflict preserved; see complaints |
| 4-year TCO (filters only) | $1,165 at official set pricing ($649 + 4×$129); $969–$1,449 across the conflicted range | Derived |
Attributed complaints & failure modes
- Bulky square footprint: consistently noted as large and hard to place (airpurifiers.com review; productnotes.com).
- Cheap-feeling buttons / no app: base 400 lacks connectivity buyers expect at this price (medium.com/@wookjong770; productnotes.com).
- Expensive filters: recurring owner complaint; the $80–90 vs $120–200 vs $129 range reflects genuine disagreement about real annual cost (conflict preserved — likely driven by usage, subscription discounts, and third-party vs genuine filters).
- Coway's subscription discount (25% off first) materially changes the math — verify at checkout.
Specialty-use notes (attributed, not our verdict)
- Positioned by reviewers for large living rooms and open plans; dual Max2 carbon units give it stronger odor/VOC credentials than typical single-filter units — reviewer inference from filter mass, not a lab VOC trial.
Community / social pulse
- UNVALIDATED on the social layer — Threads/Facebook discovery held for security review 2026-09-23; results pending (access limitation, not no-results). No direct post access; owner evidence is retailer/review-site derived.
Evidence gaps
- Whether the $129 Max2 "filter set" covers both filter units for a full year vs one side only: ambiguous from the listing — UNVERIFIED; check before purchase.
- No current measured head-to-head vs 2026 large-room peers found in the documented sample (browser searches, 2026-09-23).
Sources (full, dated)
- https://cowaymega.com/products/airmega-400 (price $649; observed 2026-09-23)
- https://cowaymega.com/collections/shop-all-products?page=2 (Max2 filter set $129; crawled 2026-09-23)
- https://productnotes.com/t/coway-airmega-300-air-purifier-review-attractive-excellent-for-large-rooms/414
- https://medium.com/@wookjong770/i-almost-returned-this-540-air-purifier-049931df6f98
- https://airpurifiers.com/product-reviews/product-review-coway-airmega-400/