Why robot vacuum suction numbers do not compare
Updated
What a pascal measures
A pascal (Pa) is a unit of pressure: one newton per square meter (NIST Guide to the SI, table 3). On a robot page it states how far the fan lowers the air pressure inside the machine. Pressure alone does not tell you how much air moves through the brush, how well the brush lifts dirt from carpet, or how much of the dirt reaches the bin.
A robot cleans with the whole path: brush, inlet, seals, filter and fan together. The suction figure describes one part of that path.
What the spec line leaves out
- The mode. Many pages write "up to", which points to the strongest setting. A quieter setting moves less air and gives a lower figure.
- The place. A pressure measured at the fan is not the pressure at the floor once air has passed the brush and the inlet.
- The method. A figure with no named test method cannot be repeated by anyone else, so a second maker cannot be held to the same conditions.
- The quantity. Some makers state air watts or a multiple of an older model instead of pascals. Those are different quantities and do not convert into pascals.
Same robot, different numbers
The dataset shows how loose the figure is, even for a single machine:
- The Roborock Qrevo 2 Pro carries 20,000 Pa on its US page and 25,000 Pa on its UK, German and global pages. Botsize stores the US figure.
- The MOVA V70 Ultra Complete reads 42,000 Pa in the US and 40,000 Pa in Germany.
- iRobot gives pascals for the iRobot Roomba Max 875 Combo Robot + AutoWash Dock on its UK page, while the US page describes the same robot as having several times more suction, without a pascal figure.
- ECOVACS states air watts for the ECOVACS DEEBOT X12S OmniCyclone and no pascal figure, and the Roborock Saros 10R pages give no figure at all, only a description.
Across the dataset, 35 of 42 records publish a pascal figure, from 8,000 to 40,000 Pa. 4 state suction another way and 3 publish no suction claim at all.
Pascals, air watts and multiples
| Stated as | What it is | Compares with |
|---|---|---|
| Pascals (Pa) | Pressure: force per area | Another pascal figure, only when both were measured the same way |
| Air watts (AW) | Power: the watt is the unit of power | Another air watt figure from the same test |
| "3x more suction" | A ratio to a model the page may or may not name | Nothing outside that page |
| A name for the motor | A brand term | Nothing |
The pascal and the watt measure different things, pressure and power (NIST Guide to the SI, table 3), so no formula turns an air watt figure into pascals without knowing the airflow as well.
What a test standard measures instead
IEC and ASTM publish a joint test method for household cleaning robots, IEC/ASTM 62885-7. Its tests cover how much debris a robot removes from hard floors and carpets, how it removes fibers from carpet, and how much energy it uses. Those are the results a buyer cares about, and a product page that quotes only pascals does not report them.
The EU ecodesign rules for vacuum cleaners from 2013, Regulation (EU) No 666/2013, cover mains powered cleaners and list robot cleaners among the types they do not apply to. Their measurement requirements do not reach a robot's suction claim.
What the finder uses instead
The robot vacuum finder decides with numbers that compare across makers because they are plain lengths and features: the climb height against your threshold, the robot height against your furniture, what the dock does, and whether the robot mops and lifts its mop. Each model page shows the suction figure in its specifications with the note that it never ranks a model.
Inside one maker's lineup, on the same page and in the same market, a higher figure points to a stronger fan in that maker's own terms. That is the one comparison the number supports.