When comparing vacuum cleaners, manufacturers often throw around technical terms like air watts, kilopascals, and even litres per second. But how do you really know how strong your vacuum is? And can you measure it yourself at home?
Here at Manchester Vacs and Dyson Medic, we test suction power using a proper analogue vacuum gauge — and we’ll explain why that matters.
What Are Air Watts?
Air watts are the vacuum industry’s preferred way of expressing cleaning performance. The number is based on both suction (pressure) and airflow — it’s calculated, not measured.
Here’s the formula:
Air Watts = (Airflow in litres/sec × Suction in kPa × 0.117)
To get an accurate air watt figure, you need to measure:
- Suction (usually in kilopascals)
- Airflow (in litres per second or CFM)
So, unless you’ve got lab-grade equipment, you can’t directly measure air watts, which is why nobody sells an “air watt” gauge. They don’t exist. It’s a calculated value, not a measurable one.
What We Measure: Inches of Water Lift (inH₂O)
We use a proper analogue vacuum gauge with two scales:
- Inner ring: 0–160 inches of water lift (inH₂O)
- Outer ring: 0–40 kilopascals (kPa)
We use the inner ring — inches of water lift — for more precise comparisons.
This tells us how strongly the vacuum can pull against a sealed surface — a good measure of raw suction. It doesn’t tell us airflow, but it gives a meaningful and repeatable number for side-by-side comparisons.
Real Suction Test Results
Here are some real figures from vacuums we’ve tested on our bench:
- Sebo X7 (890w motor):
Typically pulls 78–84 inH₂O on our gauge
(≈ 19.4–20.9 kPa) - Dyson DC14 (approx. 1600w motor):
Pulled 110 inH₂O on our gauge
(≈ 27.5 kPa)
These are real, practical measurements — not marketing numbers. The Sebo performs impressively well given its lower wattage, which speaks to efficient airflow design.
Why Can’t We Test Cordless Dysons?
Many modern Dyson cordless machines (like the V8, V10, V15, etc.) can’t be reliably tested with this type of gauge. That’s because they’re designed to detect a blocked airway, and when you attach a sealed gauge, the machine treats it as a blockage and immediately starts pulsing or shutting down.
So while some cordless vacuums may feel powerful in use, they’re simply not compatible with proper sealed suction testing like this. That’s a design choice, not a limitation of the gauge.
Can I Test My Vacuum?
Yes — with the same vacuum suction gauge we use, you can test your vacuum cleaner at home. It’s ideal for:
- Checking performance after repairs or servicing
- Comparing different machines side by side
- Spotting loss of suction over time
We supply the Marshall Town vacuum gauge — a specialist, USA-imported analogue unit that’s ideal for vacuum cleaner testing.
Final Thoughts
Air watts are fine in theory, but you can’t measure them without airflow data. What you can measure is sealed suction, and that’s what this gauge does. It won’t give you marketing numbers — it gives you real ones.
If you’re serious about knowing how your vacuum performs, or you want to check whether it’s working as it should, this gauge is a simple, reliable tool to have on hand.