When comparing power consumption with other similar devices, air-compressors and corresponding tools are not the most efficient devices out there. As a general rule, it will use approximately 7 horsepowers of electricity to produce one horsepower worth of compressed air. However, its capacity is something users need to know, which is where cubic feet-per-minute (CFM) values come into play. This tells us about the amount of air under certain pressure a compressor can produce at any given moment. How much of it is enough depends on the applications, as some tools require higher airflow than others. While impact guns and angle grinders require 2 to 5 CFM, paint-spray guns may need up to 10 CFM.