Compressor Efficiency Calculation?

First what is the compressor used for, Control air, Start air, Power tools, if of those you can use a low capacity piston compressor as air will be pressed up in air bottle. for usng air at high capacity ie, shotblasting then a vane/screw type compressor will be required. The manufactures are usualy very helpful for calculating capacity as for efficiency we all strife for 100 % but seldom achieve it.

It's generally assumed that, in compressors over 10 HP, that each HP of power will generate about 4 CFM of compressed air at 90 PSI. Much more information can be obtained about compressors and compressed air at www.about-air-compressors.com