Fan Energy Index

AMCA developed the fan energy index (FEI) in response to the 2013 U.S. Department of Energy (DOE) rulemaking, which stated that a preference for a regulatory metric to be wire-to-air (consider losses of fans, motors, and controllers); cover part-load efficiency as well as peak efficiency; and be appliable to fans rated using static or total efficiency. These properties eliminated the two fan-efficiency metrics in use at the time: Fan Efficiency Grade (FEG), which was used in ASHRAE Standard 90.1 for building-energy codes, and Fan Motor Efficiency Grade (FMEG), which was, and is still, being used in European fan regulations.

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. In other words, FEI sets an efficiency and power baseline that changes with airflow and pressure.

FEI is calculated in manufacturer sizing software during a selection process because of the many varieties of fan type, size, material and configuration options, and combinations of motor and controller options.

Standards and Codes

ANSI/AMCA Standard 208-18, Calculating Fan Energy Index, describes how to calculate FEI using data from laboratory performance tests using AMCA Standard 210 or ISO 5801, the two test procedures used worldwide for most types of commercial and industrial fans. Fans with FEG and FMEG ratings can calculate FEI from the same test data.

AMCA 208 was recently harmonized with ISO’s fan-efficiency-metric standard, ISO 12759 Fans — Efficiency classification for fans, as ISO 12759: 2024, Part 6: Calculation of the fan energy index.

FEI is the regulatory metric selected by the U.S. Department of Energy (DOE) for efficiency regulations for commercial and industrial fans and blowers. The test procedure took effect on October 30, 2023, and requires covered fans to have fans tested and rated to Code of Federal Regulations (CFR) 431.174 Test Procedure for fans or blowers.

Model energy codes, i.e.,ANSI/ASHRAE/IES Standard 90.1: Energy Standard for Buildings Except Low-Rise Residential Buildings,, has a fan-efficiency provision based on FEI starting in 2019, replacing the FEG-based provisions in the 203 and 2016 editions.

The 2021 International Energy Conservation Code (IECC) replaced FEG with FEI in its 2021 edition.

Certified Ratings Program

The AMCA Certified Ratings Program (CRP) assures buyers, specifiers, and users that a product line has been thoroughly tested and rated in compliance with rigorous test standards and rating requirements, enabling the selection of the appropriate air system components that fulfill required performance specifications.

Specify AMCA-certified FEI ratings whenever possible, even if not required by code, as manufacturers should exercise great care when updating their sizing/selection software to accommodate the motor and drive combinations available across fan types and sizes.

AMCA Publication 211-22 Certified Ratings Program Product Rating Manual for Fan Air Performance

View fan energy index licensed products by company.

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.

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.

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.

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.