FEI is a comprehensive energy metric that goes beyond brake horsepower to include the impact of all components in the fan system including the aerodynamics, motors, VFD, drives, and bearings. Brake horsepower only considers the bearing and aerodynamic losses and ignores the rest of the fan system.
FEI is simply the ratio of the Reference Electrical Input Power of a conceptual fan to the Actual Electrical Input Power of a fan system at the same duty point. The Reference Electrical Input Power is derived from actual historical fan sales data submitted by AMCA manufacturers and is intended to represent the typical power used at a specific duty point. The Actual Electrical Input Power is the power required to operate the actual fan system you are considering at the same duty point. An FEI >1.00 indicates your fan system uses less energy than the reference fan while a FEI<1.00 indicates it uses more energy than the reference fan.
If you want to dive deeper into the calculations behind FEI, read our application article.
Or let a manufacturer’s fan selection software, like Greenheck’s eCAPS®, do the work for you. Click HERE to access eCAPS and start selecting fans using FEI.
In addition to helping you compare and optimize the energy consumption of your fan system, FEI may also help you identify fan systems with better sound performance and more flexible operating ranges.
Fans with lower FEI values tend to be operating at higher speeds or may be using less efficient rotors, both of which can create more sound power. By optimizing FEI, you are selecting a fan system with a more efficient rotor or a larger fan that is operating at slower speeds, both of which improve sound performance.
Selecting a fan with higher FEI means that you are relatively more central in the fan curve, which allows you more adjustment in the field if the installed duct system is different from your design intent.
Minimum FEI requirements are now included in the current ASHRAE 90.1 standard and International Energy Conservation Code (IECC). It is now up to states or local municipalities to incorporate these into their building codes. Since 2021, several states have incorporated the current 90.1 standard into their code, thereby setting minimum FEI values. Some states lack a state-level code but are seeing adoption at the municipal level. Navigating the complex landscape makes understanding how to comply with FEI codes and regulations difficult.
To stay ahead of these ever-changing codes, design to the latest versions of ASHRAE 90.1 and IECC and include and hold duty point FEI on your fan schedule.
This timeline shows the journey FEI has taken from being published as a fan energy metric in AMCA 208 to being part of energy regulations in 15 states.
As of June 30, 2025, 18 states meet the energy efficiencies established by the ASHRAE 90.1 2019 standard and have adopted it into their codes.
Reach out to your local Greenheck representative to arrange training on optimizing fan energy performance using FEI at a convenient location for you.
