Overview
ISO 12759-6:2024 defines the method to calculate the Fan Energy Index (FEI) - a standardized energy-efficiency metric for fan duty points. The FEI provides a consistent basis to compare energy performance across fan types and sizes at a given operating point. This part of the ISO 12759 series applies to fans driven by electric motors and to fans without drives, but it is not applicable to circulating fans or air curtains. FEI calculation is limited to duty points above a minimum air power of 125 W (air power = volume flow rate × fan static pressure) or above 2.0 m³/s volume flow.
Key Topics
- Definition and scope of FEI - purpose, limits of applicability and minimum testable configurations.
- Reference electrical input power - how to derive a reference shaft power and account for transmission, motor and motor controller efficiencies to establish a reference baseline.
- Actual fan electrical input power - measurement requirements and methods for determining real input power at the duty point (including guidance on measurements and when to use tested motor data).
- Transmission and motor considerations - treatment of direct-drive, belt-driven and other transmission types and their impact on FEI.
- Measurement and calculation guidance - procedures referencing ISO 12759-2 for standard losses, ISO 5801 for performance testing, and annexed guidance for conversions (e.g., to other speeds and densities, Annex E).
- Annexes addressing practical issues - informative annexes cover fan types and test configurations, FEI pressure basis, usage guidance, fan arrays, embedded fans, and measurement conversions.
Applications
Who uses ISO 12759-6:2024 and why:
- Fan manufacturers - to report and compare energy performance consistently across product ranges.
- Specifiers and consultants - to set efficiency requirements and select fans based on FEI at required duty points.
- Test laboratories - to measure and calculate FEI following uniform methods.
- Energy auditors and facility engineers - to compare retrofit or replacement options, and to quantify fan energy savings.
- Regulators and standards bodies - to establish minimum performance bands or efficiency labeling programs based on FEI.
Practical value: FEI supports design and selection decisions that reduce operational energy use by evaluating fan performance across actual duty points rather than only at peak efficiency.
Related standards
Keywords: ISO 12759-6:2024, fan energy index, FEI, fan efficiency, fan duty point, fan performance, fan testing, energy efficiency metric.
Open preview (PDF)Fans — Efficiency classification for fans — Part 6: Calculation of the fan energy index
