Calculate Fan Energy Index from reference and actual fan electrical input power at the same duty point, or solve for either power.

From the applicable AMCA 208 method at the same airflow, pressure basis and air density as the actual power.

Electrical input including drive and controller losses, not motor shaft or nameplate hp.

Optional settings

Fan Energy Index Formula

The following formula is used to calculate the Fan Energy Index (FEI).

FEI = Pref / Pactual

Variables:

  • FEI is the Fan Energy Index
  • Pref is the AMCA reference fan electrical input power at the selected duty point (watts)
  • Reference and actual power must use identical airflow, pressure basis and air density
  • Pactual is the actual power input to the fan (watts)
  • Use consistent electrical input power units; shaft power and motor nameplate hp are not electrical input power

Divide the correctly determined reference fan electrical input power by the actual fan electrical input power at the same duty point. This calculator evaluates that ratio from supplied powers; it does not derive the AMCA reference from airflow and pressure.

What is a Fan Energy Index?

Fan Energy Index compares AMCA reference electrical input power with actual fan electrical input power at a specific duty point. An FEI above 1 means less electrical input than that reference; below 1 means more. Actual electrical input includes controller losses where applicable. Reference power must follow the applicable AMCA method. A ratio from arbitrary powers does not establish certified FEI or regulatory compliance.

How to Calculate Fan Energy Index?

The following steps outline how to calculate the Fan Energy Index (FEI).

  1. First, obtain the reference electrical input power (Pref) determined by the applicable AMCA method for the selected duty point.
  2. Next, determine the actual fan electrical input power (Pactual), including applicable controller losses.
  3. Check that both powers use the same airflow, pressure basis and air density.
  4. Convert both powers to the same unit. The hp option is a mechanical-horsepower equivalent of electrical input (745.6998715822702 W/hp), not motor shaft or nameplate hp.
  5. Use FEI = Pref / Pactual. Inverse solves rearrange this ratio; they do not independently validate the reference power.

Example Problem:

Use the following variables as an example problem to test your knowledge:

Reference and actual powers describe identical airflow at the same duty point.

Use the same pressure basis and air density for both powers.

Pactual = 1000 W

Pref = 800 W. FEI = 800 / 1000 = 0.80; actual input power is 25% above the reference.