Research · Energy efficiency
Air Purifier Energy Efficiency: CADR per Watt Across 247 ENERGY STAR Records
Most certified purifiers cluster tightly — the middle half sits between 5.81 and 7.06 smoke cfm per watt — but a small group reaches 23.96. Delivering the same 200 cfm of clean air 24/7 for three years costs about $154 at the 10th-percentile efficiency versus $95.72 at the 90th, at a hypothetical $0.16/kWh.
ENERGY STAR V3.0 · Captured 2026-10-20 (UTC) · 247 eligible records · Analysis of certification data, not independent measurements
What CADR per watt measures
ENERGY STAR reports smoke CADR (clean air delivered, in cubic feet per minute) divided by power drawn at that setting. A higher number means more clean air for each watt. It is the fairest way to compare electricity use between purifiers of different sizes, because a big unit using more watts may still be the more efficient one.
How the 247 records are distributed
| cfm/W | Records | Share | Flagged Most Efficient |
|---|---|---|---|
| 0–<6 | 88 | 35.6% | 21 |
| 6–<9 | 135 | 54.7% | 25 |
| 9–<12 | 17 | 6.9% | 16 |
| 12–<15 | 1 | 0.4% | 1 |
| 15+ | 6 | 2.4% | 6 |
223 of 247 records sit below 9 cfm/W. Only 7 reach 12 or more. The "Most Efficient" marker shown here comes from the snapshot; ENERGY STAR applies its own criteria for it, so it does not map exactly onto these tiers.
Are bigger purifiers more efficient?
Barely. The correlation between smoke CADR and cfm per watt in this snapshot is r ≈ 0.20, and the median efficiency barely moves across size ranges. Size alone does not tell you whether a model is efficient — check its own certified figure.
| Smoke CADR | Records | Median cfm/W |
|---|---|---|
| 0–<100 cfm | 49 | 5.86 |
| 100–<200 cfm | 83 | 6.34 |
| 200–<300 cfm | 44 | 6.20 |
| 300+ cfm | 71 | 6.36 |
What efficiency is worth: same clean air, different bills
To isolate efficiency, we fix the clean-air delivery at 200 cfm and ask how many watts each efficiency level needs (200 ÷ cfm per watt), then cost that running 24/7 for three years. At the 10th percentile (5.45 cfm/W) that is 36.7 W; at the 90th (8.79 cfm/W) it is 22.8 W.
| Rate | P10 (5.45 cfm/W) | Median (6.26) | P90 (8.79) | P10 − P90 |
|---|---|---|---|---|
| $0.10/kWh | $96.48 | $83.96 | $59.82 | $36.65 |
| $0.16/kWh | $154 | $134 | $95.72 | $58.65 |
| $0.25/kWh | $241 | $210 | $150 | $91.63 |
This is a what-if ceiling. Real use at lower fan speeds, fewer hours, or time-of-day pricing will cost less, and efficiency at low speed is not reported in the dataset. Filters and purchase price are not included.
The highest certified figures in this snapshot
Listed to show where the top of the range sits, not as recommendations. Noise, filter cost and retail price are not considered.
- Rainbow Luggable XL Ultra — 23.96 cfm/W · 333 cfm smoke CADR
- Rainbow Luggable XXL — 23.91 cfm/W · 306 cfm smoke CADR
- Rainbow Brisk Box Ultra — 23.27 cfm/W · 370 cfm smoke CADR
- Rainbow Luggable Ultra — 21.59 cfm/W · 231 cfm smoke CADR
- Blueair 4612522000 — 16.08 cfm/W · 82 cfm smoke CADR
Method and limits
- Source: ENERGY STAR Certified Room Air Cleaners (V3.0) records with positive smoke CADR, CADR per watt and operating power.
- Percentiles use linear interpolation; the correlation is Pearson's r for this snapshot only.
- Watts at 200 cfm and the 24/7 costs are derived scenarios, not measurements by PureAirIndex.
- See the methodology, the annual kWh study and the 24/7 running-cost guide.