Air Supply UK: Specialist Compressed Air Engineers

Published: 05/06/2024

What Is Duty Cycle On An Air Compressor?

If you’re looking to purchase or hire an air compressor – especially a reciprocating or piston air compressor – you might have come across the term “duty cycle”. If you’re unsure of what this means, or you just want to brush up on your knowledge, you’ve come to the right place! We’ve put together everything you need to know. Keep reading to find out.

What does duty cycle mean on an air compressor?

An air compressor’s duty cycle is defined by the amount of time it produces air (AKA run time) compared to its rest time. For example, if the air compressor is running at a 60% duty cycle for a one-minute cycle, it spends 36 seconds compressing the air and 24 seconds resting or idling. The total cycle time is the time it takes the compressor to complete a full loading and unloading cycle.

Mostly, you’ll see a duty cycle when referring to piston or reciprocating compressors; however, any compressor that cycles, like a rotary compressor, has a duty cycle. As every compressor is controlled by set pressure settings, when the pressure drops below a certain set level, the compressor will start, or come on load(if in idle mode). The compressor will then keep compressing air until it reaches its set maximum set pressure. Once it reaches this, it will go into stop or idle until it once again drops below the set minimum level, and then the whole cycle starts again. Some compressors stop immediately at pressure (normally piston type or smaller rotary, larger rotary compressors hit pressure, and go into a ‘run on time’, only stopping if minimum pressure not reached within the time.

How to calculate duty cycle

To calculate the duty cycle, you need to know the time the compressor is on/running and the time the compressor is off/resting. The formula is as follows:

Compressor time on \ (time on + time off) = duty cycle percentage.

For example, if your compressor is running (making air) for four minutes and then resting for six minutes in a 10-minute cycle, the duty cycle percentage rate would be 40% as the calculation would be:


4 minutes \ (4 minutes + 6 minutes) = 40%


4 minutes \ 10 minutes = 40%


The time on + time off is the total cycle time of the compressor, which is how long it runs from loading in one cycle to loading in the next. The compressor on time is the total time the compressor is actually making air.

How long can an air compressor run continuously?

Very few reciprocating air compressors are built to run continuously. So if you need your compressors to work 24/7 or produce compressed air for long periods of time, a rotary screw compressor might be better for you. This is because a piston air compressor needs time to cool down and rest between heavy periods of use, unless manufacturer states as a 100% duty machine.

If you want a compressor that works continuously without needing breaks to cool down, as mentioned above, a rotary screw compressor would be better. These air compressors are designed for applications that require a consistent supply of air over a long period of time, such as production machines and factories with constant air demand.

How Air Supply can help

Knowing an air compressor’s duty cycle, and your constant or average air demand is important, as this will help you decide what applications the compressor is good for and what size and type you should get. However, if you’re still not certain about the duty cycle and would like some help choosing the right air compressor, that’s where we can assist. Piston compressors still have their place in the market, as rotary compressors can ail through lack of use.

Here at Air Supply, we have over 25 years of experience in selling, servicing and repairing all compressed air equipment. We are specialist compressed air engineers and know all there is to know about air compressors and equipment. We sell and hire out, design and install, and repair and service new and used air equipment! Plus, if you have any questions, our expert team will be on hand to help.

Take a look at our selection of used stock or browse our new equipment. Or, if you have any questions or queries, please contact us today!

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