Buying an air compressor is complex. I’d like to simplify the process for you by providing some information that I hope is useful as you hunt down the perfect air compressor for your needs. This page addresses 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 following list will guide you to gather information from the various compressor manufacturers, 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 typically 1 HP of compressor motor size generates 3-4 CFM of compressed air at about 90 PSI from the compressor pump.
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?
Your compressed air supply and pressure requirements will drive you to select compressor manufacturers that actually make the air compressors with 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 can 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.
To figure out the running cost of prospective compressors there is another page of information about how to figure that out on this site. Costs to operate an air compressor. Don’t skip this page as the cost to operate may be the one metric that helps you decide one brand over another.
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.
What Comes With The Air Compressor?
One manufacturer has a list of included features that another shows as extra cost accessories.
What comes included with each compressor? This is a useful way to compare “apples to apples” from various compressors and manufacturers.
Maintenance Required For This Make & Model of Compressor?
What is required regarding maintenance for each compressor you are looking at? What are the mean times between maintenance functions; what are the cost of the various consumables each compressor may require, for regular and long term maintenance?
For example, if the air compressor is oil lubed, how often between oil changes, and what is the type of oil recommended? Some manufacturers recommend synthetic oils which come at higher cost. If so, what are the benefits you can expect for that greater expense?
Compressor Life Expectancy
How long will this particular model last when used for normal operating periods.
If you’ve considered under sizing your air compressor to save some capital expense up front, and end up pushing it past its acceptable duty cycle, how will that affect its life expectancy? Will you be buying another compressor much sooner than expected?
Not all warranties or guarantees are made equal. To get your business, some manufacturers may improve on their warranty. If that is the case, make sure you get any such promises in writing.
You might save a lot of money on a compressor that offers a poor warranty, yet you might find yourself replacing it completely, long before a more expensive unit, backed by a secure warranty, would have been used up.
Who Fixes This Brand of Compressor?
Do you have someone in your shop that’s capable of fixing your air compressor when the warranty expires?
If not, who will fix the air compressor then? Where are their offices, what’s the response time, are there travel expenses, and how much will it cost for a service call?
You want a company that has a good warranty, and backs it up with in-plant service, but what about the parts cost?
Once you know who will fix your compressor, ask for a parts breakdown, determine from the vendor which parts are likely to fail, and ask what the purchase price is for those parts.
There will be significant pricing disparities for similar parts from different vendors. Take the time to check as parts cost could be a large part of your compressor operating budget as time goes on.
How much does it cost to purchase each type of compressor you’ve narrowed your list down to?
Some might quote delivered your plant, others not, so add delivery / installation costs to the capital cost of each if the price quoted doesn’t include that, so that all vendor’s prices are quoted the same.
Are there any creative financing options available from the various compressor firms to help entice you to purchase from them?
Some may “carry the paper” of the loan, and if they will, and you decide not to take that benefit, perhaps refusing it might lower the cost of the unit somewhat?
Did you know that….
“Air tools … deliver more torque and higher revolutions-per-minute than electric tools, helping you complete your jobs more quickly and effectively.”