Fan Power Calculator
This fan power calculator finds the power a fan needs from the airflow, the static pressure, and the fan efficiency. Enter them and the fan power calculator returns the power in watts and kilowatts. As a fan power consumption calculator it shows what a fan draws to move air against resistance, so you can size a motor and estimate running cost.
Results
The Fan Power Calculator is part of our Ventilation collection. Browse more ventilation to size, convert, and check your work alongside this tool.
What the fan power calculator shows
A fan uses power to move air against the resistance of ducts and filters, and the fan power calculator finds how much. It multiplies the airflow by the static pressure the fan must overcome, then divides by the fan efficiency, since no fan converts all its input power into airflow. As a fan power consumption calculator it returns watts and kilowatts, the figures you need to size a motor and cost the running.
The fan power formula
The fan power formula multiplies airflow by pressure, divided by efficiency:
Q is the airflow in cubic meters per second, ΔP is the static pressure in pascals, and η is the fan efficiency. The airflow in cubic meters per hour is divided by 3600 first to reach cubic meters per second. The product of flow and pressure is the useful air power, and dividing by efficiency gives the shaft or electrical power. This fan power consumption formula is the core of the fan power calculator.
Fan power consumption calculator example
A fan moving 3600 m³/h against 200 Pa at 70 percent efficiency. The fan power consumption calculator gives:
So the fan needs about 286 watts, or 0.29 kW. Raise the pressure and the fan power calculator returns more power at once, since the fan works harder against resistance.
How to use the fan power calculator
Enter the airflow in cubic meters per hour, the static pressure in pascals, and the fan efficiency as a decimal, then the fan power calculator returns the power in watts and kilowatts. Read the airflow and pressure from the fan curve at your operating point. A fan efficiency near 0.7 suits many fans; a fan efficiency calculator can refine it if you know the exact model.
Reading the fan power calculator result
The power in watts is what the fan needs at that airflow and pressure; it sets the motor size and, over time, the electricity bill. Static pressure is the big driver, so a clogged filter or an undersized duct raises the pressure and the power sharply. To estimate running cost, multiply the kilowatts by the hours run and the electricity rate, which is what a fan electricity consumption calculator does. Size the motor above this figure, since startup and margin need headroom above the running power.
When to use the fan power consumption calculator
- Sizing a fan motor with the fan power consumption calculator
- Estimating running cost with a fan electricity consumption calculator
- Comparing fans with a fan efficiency calculator
- Rating a blower with a blower power calculator
Common fan power calculator mistakes
- Ignoring efficiency. Air power alone understates the draw; divide by the fan efficiency for the real power.
- Wrong flow units. The formula uses cubic meters per second, so the tool divides your m³/h by 3600.
- Underrating pressure. A dirty filter or tight duct raises static pressure and power well above the clean figure.
Tips for fan efficiency
- Run the fan near its best efficiency point on the curve.
- Keep filters and ducts clean to hold static pressure down.
- Multiply kilowatts by run hours and rate for the running cost.
The fan power formula and fan efficiency calculator
The fan power formula splits neatly into two parts: the useful air power, which is airflow times static pressure, and the efficiency that turns input power into that air power. The air power is fixed by the job, moving a certain flow against a certain resistance, but the efficiency depends on the fan. A well matched centrifugal fan running near its best point can reach 70 to 80 percent, while a small axial fan or a fan forced off its curve runs far lower, which is where a fan efficiency calculator earns its place. Because power divides by efficiency, a fan at 50 percent draws far more than one at 75 percent for the same air, so choosing the right fan and running it near its best point is the strongest way to cut fan power consumption.
Fan electricity consumption calculator over time
Sizing the motor is one question; the running cost is another, and a fan electricity consumption calculator answers it over time. A fan that draws 286 watts and runs continuously uses about 6.9 kilowatt hours a day, so at a typical rate the yearly cost adds up quickly, which is why ventilation fans are worth sizing and controlling carefully. Static pressure is the lever to watch, since a blocked filter or a crushed flexible duct can double the pressure and the power, so keeping the system clean pays back directly. A blower power calculator uses the same formula for higher pressure applications, and a fan power calculation kw result feeds straight into the cost sum. For the resistance side, the CFM calculator sets the airflow target that this fan power calculator then costs.
Fan power consumption calculation chart
Fan power at 1 m³/s airflow and 70 percent efficiency by static pressure, from the fan power consumption calculation:
| Static pressure | Airflow | Fan power |
|---|---|---|
| 100 Pa | 1 m³/s | 143 W |
| 200 Pa | 1 m³/s | 286 W |
| 400 Pa | 1 m³/s | 571 W |
| 600 Pa | 1 m³/s | 857 W |
Fan Power Calculator FAQ
What is the fan power formula?
The fan power formula is P = (Q x ΔP) / η, airflow times static pressure divided by efficiency. The fan power calculator applies it to give watts and kilowatts.
Why divide by efficiency?
No fan turns all its input power into moving air; some is lost to friction and turbulence. Dividing the air power by the fan efficiency gives the real fan power consumption.
How do I estimate the electricity cost?
Multiply the kilowatts by the hours run and the electricity rate. A fan electricity consumption calculator does this to turn power into a running cost.
What efficiency should I use?
Around 0.7 for many fans, though good centrifugal fans reach higher and small axial fans lower. A fan efficiency calculator refines it for a specific model.