Cordless Hoover Suction Power Explained
Suction figures on cordless hoovers come in three units that measure different things: air watts (AW) measure useful airflow power, pascals (Pa) measure pressure with the airflow blocked, and motor watts measure electricity consumed. None of them tells you how clean your carpet will be, and you cannot convert one brand's Pa figure into another brand's air watts. Use them only to compare models within the same brand.
Quick answer: Air watts are the most meaningful of the three because they combine pressure and airflow. Pascal figures (often 20,000–30,000Pa on budget sticks) are peak sealed pressure and overstate real cleaning. Motor watts only tell you energy use. Floor-head design, sealing and filtration often matter more than any number on the box.
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The physics in one paragraph
A hoover motor spins a fan that lowers air pressure inside the machine. Outside air rushes in through the floor head to equalise it, carrying dirt. Two things govern how well this works: pressure difference (how hard the air is pulled, which lifts embedded grit) and airflow (how much air moves per second, which carries debris away). Useful air power is simply the product of the two:
Air power (W) = pressure (Pa) × airflow (m³/s)
The catch is that pressure and airflow trade against each other. Block the nozzle completely and pressure peaks but airflow falls to zero, so air power is zero. Leave the inlet wide open and airflow peaks but pressure collapses. A motor's real working point sits somewhere in the middle.
The three numbers compared
| Unit | What it measures | Who quotes it | How useful |
|---|---|---|---|
| Air watts (AW) | Power in the moving air at the cleaner head or inlet: pressure × airflow at the best working point | Dyson, Samsung, some others | Most useful single figure, but brands measure at different points |
| Pascals (Pa / kPa) | Maximum pressure difference with the inlet sealed (no airflow) | Many Amazon/budget brands, Dreame, Tineco and others | Limited: ignores airflow entirely |
| Motor watts (W) | Electrical power drawn by the motor | Older corded marketing, some budget sticks | Tells you energy use, not cleaning |
Air watts in more detail
The air watt comes from a US standard (ASTM F558), originally in imperial units: airflow in cubic feet per minute multiplied by "water lift" in inches, divided by 8.5. Measured across a range of orifice sizes, the highest result is the quoted figure. For cordless sticks, numbers usually span roughly 100AW on older or entry models to well over 200AW on current flagships in boost mode.
Two caveats. First, the figure is almost always for boost mode, which you might use for a few minutes per clean. Second, some brands measure at the motor inlet and others with the wand and head attached, where losses can be significant.
Pascals in more detail
Pa is the SI unit of pressure. Standard atmospheric pressure is about 101,325Pa, so a stick quoting 25,000Pa claims it can lower internal pressure by roughly a quarter of an atmosphere with the nozzle blocked. That sounds impressive, but no cleaning happens at zero airflow. Two motors with identical Pa ratings can move very different volumes of air.
Motor watts in more detail
Electrical input is not output. Small, high-speed motors lose energy as heat and in the fan, so the air power at the nozzle is a fraction of the electrical input. The EU banned vacuum cleaners with mains motors over 900W in 2017 under ecodesign rules partly because higher wattage did not reliably mean better cleaning. Cordless machines draw far less: often 100–600W from the battery depending on mode.
A worked example: why Pa misleads
Imagine two motors, figures simplified for illustration:
| Motor A | Motor B | |
|---|---|---|
| Sealed suction (marketing figure) | 25,000Pa | 18,000Pa |
| Pressure at working point | 8,000Pa | 10,000Pa |
| Airflow at working point | 0.012 m³/s (12 L/s) | 0.018 m³/s (18 L/s) |
| Air power = Pa × m³/s | 96W | 180W |
Motor A wins the box claim but delivers roughly half the air power when actually cleaning. This is why a budget stick advertising enormous Pa figures can be outperformed by a premium machine that never mentions Pa.
What actually determines cleaning performance
- Floor head design. Bristle stiffness, brush speed and head sealing against the floor decide how much grit is dislodged from carpet. A great motor with a poor head underperforms.
- Air path sealing. Leaks at the bin seal, wand joints or filter housing waste airflow and let dust escape. This also matters for filtration.
- Cyclone efficiency. Good cyclones separate fine dust before the filter, so the filter clogs more slowly and suction stays consistent.
- Filter condition. A clogged filter restricts airflow dramatically. Most "losing suction" complaints are blocked filters or hair-wrapped brush bars; see cordless hoover losing suction.
- Battery voltage under load. As cells discharge, voltage sags. Better machines regulate motor speed so suction stays constant until the battery cuts out, rather than fading.
Suction modes and their battery cost
Air power rises steeply with motor speed, and battery drain rises with it. Typical patterns on a stick:
| Mode | Typical use | Rough share of max suction | Runtime impact |
|---|---|---|---|
| Eco / low | Hard floors, light dust | 20–35% | Longest, the basis for headline claims |
| Medium / auto | Everyday mixed floors | 40–60% | Roughly half of the eco runtime |
| Boost / max | Thick rugs, embedded grit | 100% | Often 5–12 minutes |
Auto modes that use a pressure sensor in the floor head (Dyson, Shark, Samsung and others offer versions) raise power on carpet and lower it on hard floors, which usually gives the best balance. More detail in cordless hoover battery life.
How to use specs when you're shopping
- Compare air watts only between models from the same brand, ideally same generation.
- Treat Pa figures over about 20,000 as marketing unless backed by independent test results.
- Look at independent lab results on carpet dust pickup (often reported as a percentage of test dirt removed) and edge cleaning.
- Check what floor head ships with the bundle you're buying; UK bundle variants differ.
- For carpet-heavy homes, prioritise the brush head; see best cordless hoover for carpets.
For the full buying checklist, see how to choose a cordless hoover, and for definitions of other jargon, the cordless hoover glossary.
FAQs
How many air watts is good for a cordless hoover?
As a rough guide, 100–150AW in boost suits flats and hard floors, and 150AW-plus suits carpet-heavy homes. But floor head design matters as much, and figures are only reliably comparable within one brand.
Can I convert Pa to air watts?
Not reliably. Air watts need both pressure and airflow at the same working point, while a Pa rating is usually measured at zero airflow. Without the airflow figure, any conversion is guesswork.
Is 25,000Pa suction good?
It is a high sealed-pressure claim, but on its own it doesn't tell you how much air the hoover moves. Many budget sticks quote similar figures with very different real cleaning results, so look for independent tests.
Why does my hoover feel weaker as the battery runs down?
Battery voltage drops as cells discharge, and cheaper machines let motor speed fall with it. Better designs regulate the motor to hold suction constant, then cut out. A clogged filter has a similar effect, so check that first.