# What efficiency should an industrial centrifugal fan or blower reach?

Canonical: https://senseible.earth/answers/centrifugal-fan-efficiency-by-type

BEE gives peak efficiency ranges by fan type: 79 to 83% for airfoil, backward curved or inclined blades, 72 to 79% for modified radial, 69 to 75% for radial, 58 to 68% for pressure blowers and 60 to 65% for forward curved. Measure your fan's flow, pressure and shaft power and compare.

## Peak efficiency by type

- Airfoil, backward curved or inclined: 79 to 83%
- Modified radial: 72 to 79%
- Radial: 69 to 75%
- Pressure blower: 58 to 68%
- Forward curved: 60 to 65%

## How to measure your fan

1. Measure average velocity pressure across the duct with a pitot tube and inclined manometer, in mm water column.
2. Velocity (m/s) = Cp x square root of (2 x 9.81 x velocity pressure / gas density). Use the pitot maker's Cp, or 0.85.
3. Flow (m3/s) = velocity x duct area.
4. Shaft power (kW) = electrical input (kW) x motor efficiency.
5. Static efficiency (%) = flow x static pressure (mm WC) / (102 x shaft kW) x 100. Use total pressure for mechanical efficiency.

## Usual fixes when a fan is low

- Fit a VFD where flow varies, instead of throttling with a damper.
- Replace an oversized fan with one sized for the real load.
- Keep the suction clean and clear, and plug duct leaks.
- Replace rewound motors with IE3 motors.

## Example: a backward curved process fan (illustrative)

- Flow 10 m3/s, static pressure 150 mm WC
- Electrical input 25 kW, motor efficiency 92%: shaft power 23.0 kW
- Static efficiency = 10 x 150 / (102 x 23.0) x 100 = 63.9%
- That is well below the 79 to 83% peak for this fan type, so look at dampers, sizing and leaks

Readings are illustrative.

## What Senseible does here

Senseible tracks your plant's monthly units from bills, which shows whether a fan fix moved the total. It does not take fan readings.

- [VFD savings on pumps and fans](https://senseible.earth/answers/vfd-pump-fan-energy-co2-savings)
- [IE2 to IE4 motor replacement](https://senseible.earth/answers/ie2-to-ie4-motor-replacement-savings)
- [Pump efficiency tests](https://senseible.earth/answers/pump-efficiency-test-and-replacement-savings)

Sources: [BEE, Energy Conservation Guidelines for MSME Sector (2019): section 5.3 and Table 5.6 (from BEE guide book for energy managers and auditors, chapter 3.5)](https://beeindia.gov.in/WriteReadData/L45218/1734411984.pdf)

Last reviewed 2026-10-24.