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Knowing your Watts from your Amps

4 Min Read

  • Buying Guide

What's a Watt? When it comes to choosing a new vacuum cleaner, understanding the difference between Watts, amps and volts leaves a lot of us in the dark. Yet, many of us will choose one model over another simply because it has a higher Watt rating.  But does that really mean it's more powerful? We’ve put together a guide to help you understand exactly what all the tech-talk means. So, the next time you're out looking for a new vacuum cleaner, read on and find out exactly what to compare so you can make your next purchase with confidence.


Watts (the amount of energy consumed per unit of time) measure the power of the motor inside the vacuum cleaner at maximum capacity, but not the overall efficiency or performance of the machine.

Less efficient motors  (motors that are capable of taking a greater load than the fan needs it to) will have a high wattage value, but this doesn't necessarily mean that the suction power is better. Vacuum cleaners with low Wattage don't always have it advertised as a feature. As such, it is not always the most accurate tool to use when comparing vacuum cleaners, but despite this is still the most common method.


Amps are more commonly given out by manufacturers in the US, it rates the electrical usage of all the components of the vacuum cleaner put together, but not the overall efficiency. The maximum number of amps that can be used by an electrical appliance in the UK is 13 Amps.


In the UK, the voltage that all domestic appliances run on is 240V. This is the standard voltage of electricity outlets.  The only exception to this in the UK is a specialist 110V electrical supply system for machines (including vacuum cleaners) that are built for use with 110V Centre to Earth (CTE) power transformers. These are a legal health & safety requirement on building sites.  They have a yellow three-pin plug as opposed to the British standard three-pin and won’t work in your home.

Water lift

In the US, vacuum cleaners are often put through a water lift test to see how powerful the suction is. The unit is sealed and attached to a tube of water. The test is to see how far the machine can lift the water level. In basic terms, the higher the water lift the better the suction power of the machine. The highest value is seen when the airflow is blocked, but it doesn't reflect normal conditions. It does however, show how well a blockage could be cleared by the suction power.


In Europe, the kPa (kilo Pascal) is the metric measurement used to show the maximum suction pressure. Very similar to water lift, this value is also highest when the airflow is blocked therefore it is only a peak value and not a cleaning value that is comparable to other vacuum cleaners. It does show how well a blockage could be cleared by the suction power.

Air watts

An Air Watt is a way to define the suction power of a vacuum cleaner. More specifically, it measures the energy of the suction airflow created by the vacuum cleaner. It gives a more accurate indication of performance than looking individually at other measurements, as it was specifically invented to give consumers the tools to make more informed decisions when comparing products, and is only used on vacuum cleaners.

When testing the air watts, the air inlet size is gradually reduced in order to simulate everyday blockages that can occur in vacuum cleaners. The best result is somewhere in the middle range, where suction power and airflow are maintained at a good level during the partial blockage.

Understanding Air Watts Graph



Depending on what you are using your vacuum cleaner for, how much dust it filters is very important to consider. The better the filter, the finer the dust particles it captures and prevents from passing back into the air you breathe. The highest rated filters on domestic machines will filter 99.97% of dust and allergens as small as 0.3 microns. Machines with a higher level of filtration must have a higher power to enable it to pull debris through the complex filter. The often means that vacuums with a HEPA filter are more expensive, because of the higher level of airflow they demand.

PTO (Power Take Off)

Power Take Off (PTO) is a term used to describe an additional power socket that is fitted onto a vacuum cleaner unit. Most commonly used for plugging in electric power tools for synchronised dust extraction, some PTO sockets also feature an integrated switch that enables this. Our best-selling VQ1220PFC Multi 20 is prime example of a vacuum cleaner with PTO.


Capacity is simply the size of the collection tank on your vacuum cleaner. Smaller capacity means you must empty your machine more often to avoid losing suction power. The bigger the capacity, the larger the airflow and cleaning ability. When considering the capacity, you’ll need, think about how often you use your vacuum cleaner and what you’re vacuuming, bigger is not necessarily better when it comes to being economical.


Depending on where you want to use your vacuum cleaner, noise can be a deal-breaker. The more power the machine has, naturally it will be louder, but some vacuums are louder than others. It is always worth checking the decibels (dB) of the device.

There are two dB measurements, Sound Power (cause) and Sound Pressure (effect). Sound Power is the noise emitted by the machine, this is the louder of the two, and is often quoted by manufacturers. Sound Pressure is the noise measured by the time it reaches your ear, and is always the quieter of the two.

To give you an idea of what decibels mean, a normal conversation at home is usually rated around 50dB, while a lawn mower is around 90dB, and a car horn is around 110dB. The average vacuum cleaner is around 80dB, but there are models out there that are designed to operate quietly. A quiet vacuum cleaner would operate at around 65-75dB, for example our Vacmaster Quiet operates at 72-74dB.

Don’t leave it there!

Of course, there are a range of other factors that will influence your decision when purchasing a vacuum cleaner, not just the Watts! The price, brand, look and specific features to suit your personal needs are all important.  We hope our technical guide helps you find the best  vacuum cleaner, with the right specification for what you need and helps you get the most for your money.

If you have any questions don’t hesitate to get in touch by leaving a comment in the section below or send us an email at