This standard defines the calculation method for the fan energy index (FEI), which is an energy efficiency metric for fans inclusive of motors and drives. This metric provides a standardized and consistent basis to compare fan energy performance across fan types and sizes at a given fan duty point. Fan specifiers can use FEI to understand and communicate the fan efficiency design intent. Legislative or regulatory bodies can use FEI to define the energy efficiency requirements of fans. The scope includes all fan and motor sizes and all applications, including fans with fan air performance based on tests in accordance with one of the following fan test standards: ANSI/AMCA Standard 210, ANSI/AMCA Standard 230, ANSI/AMCA Standard 250, ANSI/AMCA Standard 260, ISO 5801, or ISO 13350. All other fans are excluded (including air curtain units that are tested in accordance with ANSI/AMCA Standard 220).