Fan Energy Index

AMCA developed the fan energy index (FEI) in response to the 2013 U.S. Department of Energy (DOE) rulemaking, which preferred a metric based on electrical power consumption, different from the fan efficiency grade (FEG) metric.

FEI measures the efficiency of the entire fan system, including the fan, motor, and drive, instead of just the fan itself. It sets an efficiency and power baseline that changes with airflow and pressure and can be applied to most commercial and industrial fans and blowers.

This index is calculated using data from laboratory performance tests and can be found in manufacturer sizing software and product catalogs. Unlike other metrics, FEI does not set a peak-efficiency threshold but establishes a "range of compliant operations." This means that FEI optimizes fan, motor, and drive selections for the specific conditions under which they will operate.

Benefits

Clarity for Buyers and Specifiers

FEG ratings cover a range of sizes for a particular fan model, which hides the lower actual efficiencies of smaller fans. For example, a FEG 67 rating applies to a range of efficiencies, from approximately 45% to 65%, depending on the impeller diameter. Generally, larger fans are more efficient. To address this, designers need to use a sizing window to encourage fan selections to larger diameters. FEI ratings solve this problem by providing values that accurately reflect the actual efficiency of a fan.

Simpler Design and Code Enforcement

To make the FEG metric useful in energy codes and for selecting energy-efficient fans, a specified sizing window is required, the selection window is 15 percentage points in baseline codes, such as ANSI/ASHRAE/IES Standard 90.1-2013 and -2016, and 10 percentage points in stretch/green codes, such as ANSI/ASHRAE/IES/USGBC Standard 180.1-2014 and -2017. This means that fans must be rated for total efficiency, even though static-pressure ratings are commonly used, and fan selection must fall within the specified sizing window. Designers must document the selection of every fan, and code officials must ensure compliance with the sizing window. 

Ignoring the sizing window may lead to the selection of smaller fan sizes due to lower first costs, resulting in higher energy consumption and life-cycle costs. On the other hand, FEI works for both static and total efficiency and eliminates the need for the cumbersome window.

Application Flexibility

Manufacturer software offers compliant fans of various types, sizes, materials, and motor/drive combinations when a designer inputs a fan selection or duty point. This makes cost-benefit analyses for fans with higher FEI ratings easier. It also allows for comparisons across fan types, not just options within a single fan type.

Greater Energy Saving

FEI saves energy compared to FEG by making it easier to use and enforce, and by encouraging the use of more efficient fan types, sizes, and motor/drive combinations.