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Calculation Machine

Fan Power Calculator

Brake horsepower and running cost of a fan.

Reviewed by James Whitfield · How we check our maths

Your values

ⓘ Live results

Results
Brake horsepower
0.484 hp
Input power
0.401 kW
Annual energy
1,203 kWh
Annual cost
$192.53
Watts per CFM
0.201

Quick answer

Fan brake horsepower equals CFM times static pressure divided by 6356 times the fan efficiency.

The formula

BHP = CFM x SP / (6356 x efficiency)

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Airflow2000 CFM
  • Static pressure1.0 in w.c.
  • Fan efficiency65 %
  • Run hours per year3000 h
  • Electricity rate0.16 $/kWh

Result

  • Brake horsepower0.484 hp
  • Input power0.401 kW
  • Annual energy1,203 kWh
  • Annual cost$192.53
  • Watts per CFM0.201

How to use the Fan Power Calculator

  1. 1Enter airflow and the static pressure the fan works against.
  2. 2Use the fan's efficiency from its curve, typically 55–70%.
  3. 3Add run hours and your electricity rate to see the annual cost.

Frequently asked questions

What is a good watts per CFM?

Efficient residential ventilation runs under 0.4 W/CFM; poor systems exceed 1.0.

Why include motor efficiency?

Brake horsepower is shaft power; the motor draws more from the wall, typically 10–15% extra.

About this calculator