What Are Air Watts in Vacuum Cleaners?

Written by James Hall |

A guide to air watts for vacuum cleaners

Confused about air watts for vacuums? You’re not alone! Here’s a simple guide to air watts and why they can be a useful rating when buying a vacuum cleaner.

Comparing vacuum cleaners can be difficult.

There’s no single rating to compare the performance of two (or more) vacuums. Most brands are also more interested in promoting features rather than cleaning performance.

In an attempt to make things easier, some vacuum cleaner manufacturers list “Air Watts” as part of their vacuum specifications.

Unlike regular watts, this metric is meant to measure the vacuum’s suction power. But how is it calculated? And is it a useful rating…or just another marketing gimmick? Let’s find out!

What Exactly Are Air Watts in Vacuums?

Air watts (AW) is a way to measure the suction power (or output) of a vacuum cleaner.

We’ll get into the formula for Air Watts later, but the calculation involves both airflow (the amount of air flowing through the vacuum) and water lift (how much water the motor is capable of picking up.)

Air watts are also typically measured after resistance from filters, bags, and leaky tubes, so it (theoretically) provides an accurate measure of a vacuum’s real suction power.

How Does Air Watts Differ From Watts?

Despite the similar name, there’s a big difference between air watts and watts. Air watts measure the output of a vacuum, while watts is just the amount of input provided to the motor.

To break this down further:

  • Watts – This is just how much power is being drawn by the motor. Much of this power is lost as heat, noise, and due to the vacuum’s efficiency, so watts are not a good indicator of a vacuum’s performance.
  • Air Watts – This is related to the actual air flow of the vacuum cleaner, taking into account air leakages and filters.

In other words, air watts are a much more useful measure than motor wattage when buying a vacuum cleaner.

While a higher wattage can boost air watts, the amount of increase depends on the motor’s efficiency, whether the vacuum is fully sealed, and which filter is being used.

That means a higher wattage doesn’t mean that a vacuum provides better suction power.

This is why the EU brought in new rules that limit a vacuum cleaner’s motor power to 900W. Until this change, vacuum cleaners were being built with more and more powerful motors (2500W+ in some cases), yet were inefficient and loud.

Note: The efficiency of a vacuum is usually defined as the ratio of air watts to input watts.

Are Air Watts a Useful Metric?

Air watts can be an interesting number to look at when choosing vacuum cleaners – and the measure is certainly more useful than watts – but there are some limitations.

  1. Air watts only measures the suction power of a vacuum cleaner, not dust pickup. The amount of dirt, dust, and hair a vacuum can remove isn’t just dependent on suction, but also on the floorhead and brush bar.
  2. Many manufacturers don’t publish air watts for their vacuums, as there is no obligation to do so. This makes comparing vacuums difficult.
  3. It’s important to check where airflow is being measured, as this affects the air watts calculation. For a true estimate of suction power, the airflow must be measured at the cleaner head.

In reality, the biggest issue is #2: most manufacturers don’t provide air watt figures for their vacuums. Without being able to compare vacuums using the same rating, air watts becomes much less useful.

Note: Air watts are measured with a clean filter and unobstructed airflow. A clogged filter greatly reduces suction power, which is why it’s important to properly maintain your filters. We’ve written a guide for maintaining suction power which may be useful if your vac is losing suction.

How Are Air Watts Calculated?

There are several ways to calculate air watts, but the most common is:

Power in Air Watts = 0.117354 x Airflow (CFM) x Water lift (inches of water)

Where “inches of water” is the amount of pressure during a water lift test, and the airflow is measured in cubic feet per minute (CFM.)

Note: Water lift is a common sealed suction power test for vacuum cleaners. During this test, the vacuum is sealed and connected to water via a tube. The amount of water lifted by the vacuum determines the water lift.

Are The Air Watts of Dyson, Shark, and Other Vacuum Brands the Same?

There’s more than one way to calculate air watts, but the difference is minimal. That means you can theoretically use this value to compare vacuum cleaners from different brands.

Unfortunately, most brands don’t publish information about the air watts of their vacuums. It’s also important to remember that air watts won’t tell you about the cleaning performance of the vacuum, just the suction power.

Does an Air Watts to Watts Calculator Exist?

No, because two vacuums with the same input watts can generate very different air watts. The amount of suction depends on a variety of factors, such as the vacuum’s efficiency, filter type, and whether the body is fully sealed.

How Many Air Watts Does a Good Vacuum Cleaner Generate?

As a general rule, an upright vacuum cleaner needs at least 100AW, while a cylinder vacuum cleaner needs around 220AW (these figures were provided by Hoover.)

This isn’t an easy to question to answer, however, as air watts are just one way to measure a vacuum cleaner’s suction power.

As we mentioned earlier, air watts don’t measure how effective a vacuum is at picking up dirt and other debris. Along with suction power, cleaning performance depends on the vacuum’s floorhead design, brush bar strength, and various other factors

The type of vacuum also affects the required air watts. A cylinder vacuum, for example, needs more suction to pull dirt along the long hose. Vacuum’s with HEPA filters (or other types of advanced filtration to prevent allergens escaping) also need greater suction to force air through the dense filter material. Bagged or bagless vacuums may also require different minimum air watts.

Summary

Air watts are a measurement of a vacuum cleaner’s suction power. This rating is much more useful than the watts of a vacuum cleaner, as it measures the output suction, rather than how much power is used by the vac.

There are limitations to air watts though. The measurement doesn’t indicate the cleaning performance of a vacuum, as suction power is only one element of a vac’s ultimate performance. Many vacuum brands also don’t provide air watts for their models.

Even so, air watts are still one of the most useful measurements for comparing the suction power of vacuum cleaners.

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