The Truth about Horsepower Ratings in Vacuum Cleaners

Most manufacturers of garage vacuums and shop vacuums are marketing their vacuums as 4-5 Peak Horsepower (PHP). Desert Equine would like to address and clarify this highly misleading practice. No matter what you call it, PHP, HP or horsepower -  it's all just horse hockey when it comes to the performance of a vacuum cleaner.

To put it into the simplest terms:

When it comes to vacuum cleaners, horsepower is a bogus, fictitious number having no relationship to the performance or cleaning ability of the product.

It is not based upon the nominal operating current of the vacuum cleaner, but rather on the in-rush current to the motor upon initial power-up.

The peak in-rush current lasts no more than 0.008 to 0.012 seconds. It is often exaggerated by chilling the motor to temperatures as low as -20°F.

For example, 4-horsepower equates to 2,983 Watts, or 24.9 Amps at 120Volts under ideal conditions. This would greatly exceed the voltage supply circuits and blow the circuit breaker in a home.

It is nothing more than a 100% marketing gimmick. In other words, it's just horse hockey.

For the technical person:

Horsepower is not based upon the normal operating current of the motor. It is calculated using the maximum in-rush current. In-rush current is the current a motor sees when first started up; before the effects of winding inductance come into play. A motor with a nominal operating current of 12A can easily have an in-rush current of 30A to greater than 50A, depending upon the windings. It typically lasts for only 8 to 12 milliseconds (0.008 to 0.012 seconds). Some manufacturers attempt to maximize the in-rush current by conditioning the motor to very low temperatures (as low as -20°F). This lowers the motor's resistance, thus increasing the in-rush current.

Power is equal to Volts times Amps. Even when ignoring the efficiency and power factor of the motor, a motor with a nominal 12A current @ 120V will only produce 1,440 Watts. There are 745.7 Watts per Horsepower. Thus, under the best of conditions, the motor will only produce 1.9 hp. A motor touting 4-HP would have to produce 2,983 Watts. With that power, the motor would be drawing 24.9 Amps. Horsepower is strictly a unit of measurement for the motor (without any fan blades), not the vacuum cleaner system; and does not take into account any normal system losses (air leaks, restrictions, piping, etc).

This became such an issue in the late 1980s and early 1990s that Underwriters' Laboratories and the Canadian Standards Association put wording into the vacuum cleaner standard prohibiting horsepower from appearing on the product's electrical rating label.