An air compressor is a device used to compress gas. Air compressors are similar in construction to water pumps. Most air compressors are reciprocating piston, rotary vane or rotary screw. Centrifugal compressors are used in very large applications.

Air compressor energy consumption is affected by isothermal efficiency, ambient temperature, mechanical efficiency, inlet/discharge pressure, and air volume. Optimizing operations, regular maintenance, and adjusting parameters can reduce energy use