The pascal (Pa) is not a unit of suction power. It measures vacuum pressure — the difference in air pressure between the inside and outside of the machine. In a Korea Consumer Agency survey, six cordless vacuums advertising maximum suction of 18,000 to 48,000Pa actually delivered between 58 and 160W. Of the ten products examined, only three met the numbers printed on the box.
The same level of performance gets written as 200 by one maker and 20,000 by another. With two orders of magnitude between them, laying spec sheets side by side stopped being a meaningful exercise. That is why Korea's national standards body decided to write a Korean Industrial Standard (KS) for it.
W, AW and Pa Measure Different Physical Quantities
These are not rival notations for the same thing. Based on published test criteria, they break down like this.
| Unit | What it measures | Standard | Typical magnitude | Makers using it (in the survey) |
|---|---|---|---|---|
| W (watt) | Suction power = airflow × vacuum pressure | IEC (international) | Tens to hundreds | Samsung, LG |
| AW (air watt) | Suction power (same concept, different test conditions) | ASTM (US) | Tens to hundreds | Dyson, Dreame |
| Pa (pascal) | Vacuum pressure only | SI unit of pressure | Tens of thousands | Ionic, Iroom, Xiaomi, Dibea, Roborock, Tineco-class brands |
The crux is that W and AW are units of work while Pa is a unit of pressure. As Electimes lays out the formula, suction power in watts is the product of airflow drawn into the machine (L/s) and vacuum pressure (Pa). A large Pa figure means one term of that multiplication is large. It guarantees nothing about the result.
Whether 20,000Pa Is a Lot Depends Entirely on Airflow
In SI units, Pa × m³/s = W, so multiplying kPa by L/s gives watts directly. Take the advertised pressure range found in the survey (18–48kPa) and pair it with realistic airflow figures:
| Vacuum pressure (kPa) | At 2L/s (W) | At 3L/s (W) | At 4L/s (W) | At 5L/s (W) |
|---|---|---|---|---|
| 18 | 36 | 54 | 72 | 90 |
| 25 | 50 | 75 | 100 | 125 |
| 35 | 70 | 105 | 140 | 175 |
| 48 | 96 | 144 | 192 | 240 |
Read a row across and doubling airflow doubles suction at identical pressure. Read a column down and it gets more interesting: a machine at 48kPa but only 2L/s (96W) is effectively matched by one at 18kPa with 5L/s (90W). The advertised pressure differs by a factor of 2.7 while the actual work done is near identical. Compare the Pa figures alone and that entire relationship vanishes.
One caveat on the arithmetic. Those products are theoretical ceilings. Peak vacuum pressure occurs when the inlet is fully blocked — that is, when airflow is zero. Peak airflow occurs at the lowest pressure. The two maxima never coexist, so multiplying the two headline numbers from a catalogue yields more than any real machine can produce. This is precisely why the IEC-based watt rating is measured at the operating point where the product of the two is greatest.
Pascals tell you how hard it pulls; airflow tells you how much it pulls. Cleaning is the product of the two.
Three of Ten Met Their Stated Numbers
Separate from the unit confusion, there was the question of whether the printed figures held up at all. Here is what the joint Korea Consumer Agency and Korea Testing Laboratory testing found, as reported by Consumuch.
| Product | Stated unit | Stated value | Measured suction | Met claim |
|---|---|---|---|---|
| Samsung, LG | W | 280W | 280W or above | Yes |
| Dyson | AW | — | 280W or above | Yes |
| Dreame | AW | 150AW | 121W | No (about 80%) |
| Six Pa-labelled products | Pa | 18,000–48,000Pa | 58–160W | Not comparable |
Converted to watts, the six Pa-labelled machines land in a band of 58 to 160W. Against the 280W of the three that met their claims, the bottom of that band is roughly one fifth. In marketing copy the contest was 48,000 versus 280, an apparent rout. Restate both in the same unit and the ranking inverts. The gap between printed specifications and real performance is the same pattern that has recurred in how air purifiers state their coverage area.
What the KS Standard Changes
According to ZDNet Korea, the Korean Agency for Technology and Standards published the draft standard for a 60-day comment period beginning 18 September 2025 and set out to finalise an IEC-aligned KS for cordless vacuums by early 2026. Once in place, suction ratings are to be stated uniformly in watts.
A KS is a voluntary standard, however, not a mandatory certification. It creates a basis for uniform labelling; it does not instantly rewrite every product listing. Overseas direct-purchase channels and open-market product pages in particular are likely to lag. For now, assume you are comparing a mix of Pa and W labels.
What to Check Before You Buy
- Identify the unit first — if the listing quotes maximum suction in Pa, that number cannot be compared with another product's watts. Hunt down a W or AW figure in the manufacturer's spec document.
- Treat W and AW as approximate — both express suction power, but IEC and ASTM measure under different conditions. Identical numbers do not prove identical performance.
- Look for the airflow figure — if L/s or CFM appears alongside pressure, you can multiply them yourself for a rough ceiling.
- Check runtime in max mode — suction ratings are quoted at maximum. If that mode lasts only a few minutes, real-world performance sits well below the headline.
- Confirm whether the KS was finalised — the status after the comment period is posted by the standards agency. For units released after adoption, buy on the watt figure.
If a Pa number already steered a purchase, the same brand's robot vacuum suction ratings most likely carry the identical labelling problem. Changing categories rarely changes a manufacturer's habits.
Sources
- Cordless vacuum suction labels vary wildly — standardisation from next year (ZDNet Korea)
- Comparing cordless vacuum suction: pascal figures bear no direct relation (Consumuch)
- Products labelling suction in pascals risk misleading consumers (Domin Union News)
- Cordless vacuum suction labels to be unified in watts (Electimes)