Air Tool Efficiency

• 16kW to produce 100CFM at 100PSI - [1]
• 0.4 kW takes 20 CFM - [2]
• The above 2 numbers point to 3kW for 20 CFM - to get 0.4 kW out - or 13% efficiency of air tools. Extremely low.

More:

• 0.3kW for 7 atm CFM - [3]
• Thus yes, if a tool needs 20 CFM at 7 atm - or 7 kW for its output. that is less than 10% efficient.

Links

• This post supports overall efficiency being about 5% - [4]
• Low Tech Magazine on Compressed Air Storage
• Rotary Screw Compressor