Buying An Air Compressor


Buying an air compressor is complex. Here is much of what you need to know to help you when selecting and then buying your air compressor, whether it be for a shop or home workshop use.

The process of buying an air compressors can be quite complex for someone not in the industry already. I'd like to simplify the process for you, by providing useful information to help you in your search.

I have prepared the following information list for you to use, to gather information from the various compressor manufacturers you talk to, to help you decide which company, which type of air compressor, or which feature(s) provides you the best value for your compressor needs.

Compressed Air Requirements

If you haven't yet determined your total CFM requirements are, and at what pressure you need that compressed air delivered, you can't be expected to select a compressor that suits. You really must do this first.

Please see these links for further information about sizing an air compressor, and if you are looking for an air compressor to run air cylinders, information on how to select a compressor that is suitable.

Remember, when you're sizing your compressor, that 1 HP of compressor output generates about 4 CFM of compressed air at about 90 PSI.

This is the accepted wisdom for air compressors over 10 HP in size. For smaller compressors, those under 10 HP, you must rely on the figures provided by the manufacturer or "guestimate" that you're getting around 2-3CFM of compressed air per HP @ 90 PSI.

Compressed Air Losses

Remember too that, over time in a typical plant environment, you can expect to lose about 10% of your overall air production through compressed air misuse or leaks, and through pressure drop in the system. You do want to allow for this.

Where are planning to be in 5 years regarding compressed air-related demand. Allow for expected growth.

Continuous Run or Start & Stop Compressor?

Whether your compressor should be a continuous run style, or one that starts and stops based on the pressure cycle, may be answered by your demand requirements. If it isn't clear cut, talk to the manufacturers about their benefits for a compressor that fills a reservoir and stops until low pressure signals a start, or one that runs continuously, but only compresses air as the demand is there.

Field portable units, which often run on gasoline or diesel, are usually continuous run, as the need to start and stop a fossil fuel motor every few minutes is negative to the motor.

Portable or Fixed Installation?

Are you planning to take it with you to various locations or job sites, or is this air compressor heading for a fixed installation?

While most plants rely on fixed installations, there will be many applications for portable air compressors too. If that's your choice, you need to discuss with the vendors the methods of portability; is the air compressor carried, come already installed on a wheelbarrow or cart, is the compressor itself wheeled, trailer type, etc.? You discuss this with the compressor sales outlet based on your expected needs.

Available Power Supply?

Regardless of the type of compressor you purchase, it will have to have a power supply. If it's to be installed in a plant, what voltages or amperage's do you have available? To get the volume of air you need, will you have to upgrade your electrical system?

Since the amount of power available in a typical home 120 VAC circuit limits the size and therefore the volume of air from the compressor, if you are planning on running high demand air tools or multiple tool locations, you will want to look at 220 VAC systems.

If it's a portable style of compressor, do you want it powered by gasoline, diesel or perhaps propane? Are there any other power options available or necessary for you, depending on where you are in the world?

Operating Costs?

Your compressed air supply and pressure requirements will drive you to select compressor manufacturers that actually make compressors of the capacity and flow that you require.

Then, the available power supply may further narrow the list of vendors to those that can provide a unit that runs on the power you have available or that you choose to use.

Regarding electrically driven compressors, higher voltage units sometimes generate compressed air at lower cost. Ask about the voltages available from that vendor, and your benefit as it pertains to lower operating costs depending on that voltage.

Perhaps you might find that a propane unit offers lower operating costs than gasoline if you need a portable unit.

If you are looking at a plant or production environment, I suggest you determine from each compressor vendor their equipment efficiency, and then, plugging in the energy costs where you are, compare energy consumption costs for each. There may be significant differences, and choosing wisely up front, can save you or your company a great deal of money over the life of the air compressor.

Over the life of the air compressor, the operational energy and maintenance costs will outweigh the initial capital cost of the air compressor by a wide margin.