A fan efficiency grade (FEG) is a measurement for determining an HVAC fan’s energy efficiency.
The FEG measures the fan ability to convert its shaft or impeller power into air power. It takes the shaft/impeller power and then controls for aerodynamic, mechanical, and acoustic losses, with the result being air power. The equation is as follows: Air Power, Ho ≡ PT Q
The HVAC industry uses FEGs to define any given project’s energy efficiency needs. FEGs let project engineers understand what kinds of fans and shaft power systems they need to look into to meet their clients’ energy efficiency requirements (e.g., to meet LEED Gold).