Wind Turbine Power Output Calculator

Calculator Inputs

Air Density (kg/m³)

Sea-level standard is about 1.225 kg/m³.

Rotor Diameter (m)

Used to calculate swept area.

Wind Speed (m/s)

Power changes strongly with wind speed cubed.

Power Coefficient (Cp)

Betz limit caps Cp at 0.593.

Drivetrain Efficiency (%)

Mechanical transmission efficiency.

Generator Efficiency (%)

Electrical conversion efficiency.

Availability Factor (%)

Accounts for downtime and maintenance losses.

Number of Turbines

Use 1 for a single turbine estimate.

Cut-in Speed (m/s)

Below this speed, output is zero.

Rated Speed (m/s)

At or above this speed, rated power may apply.

Cut-out Speed (m/s)

At or above this speed, output is zero.

Rated Power per Turbine (kW)

Optional cap for realistic turbine output.

Example Data Table

Air Density	Diameter	Wind Speed	Cp	Drive %	Generator %	Availability %	Turbines	Farm Output	Daily Energy
1.225 kg/m³	80 m	9.5 m/s	0.41	93	96	97	3	2,811.76 kW	67,482.17 kWh

This example uses cut-in 3 m/s, rated speed 12 m/s, cut-out 25 m/s, and rated power 2000 kW per turbine.

Formula Used

1. Swept area: A = π × (D / 2)²

2. Wind power in airflow: P_wind = 0.5 × ρ × A × v³

3. Mechanical capture: P_mech = P_wind × C_p

4. Net electrical output: P_net = P_mech × η_drive × η_generator × Availability

5. Farm output: P_farm = P_net × Number of Turbines

The calculator also applies practical operating limits. Output becomes zero below cut-in speed and at or above cut-out speed.

If rated power is entered, the result is capped at the rated value. If rated speed is entered, the calculator uses rated output at and above that speed until cut-out.

Because wind speed is cubed in the equation, a small speed change can produce a large power change.

How to Use This Calculator

Enter the local air density or keep the default standard value.
Enter rotor diameter and current wind speed.
Set the power coefficient based on turbine performance data.
Enter drivetrain, generator, and availability percentages.
Add turbine count for farm-level estimates.
Set cut-in, rated, and cut-out speeds for realistic operation.
Optionally add rated power per turbine to cap the output.
Press Calculate Output to view results, graph, and downloadable reports.

FAQs

1. What formula does this calculator use?

It starts with 0.5 × air density × swept area × wind speed cubed. Then it applies power coefficient, drivetrain efficiency, generator efficiency, and availability. Rated power and speed limits can also be used for more realistic output behavior.

2. Why does wind speed affect output so much?

Wind power is proportional to the cube of wind speed. Doubling wind speed can increase available wind power by about eight times, before turbine limits and losses are applied.

3. What is air density in this calculation?

Air density measures how much mass exists in a volume of air. Denser air carries more energy through the rotor, which increases potential power output at the same wind speed.

4. What does the power coefficient mean?

The power coefficient, or Cp, represents how much of the wind’s available power the turbine can capture mechanically. It cannot exceed the Betz limit of 0.593.

5. Why does the output become zero at high wind speeds?

Turbines shut down at or above cut-out speed to protect the machine from excessive mechanical stress and unsafe operating conditions. That is why output drops to zero.

6. What happens when rated power is lower than the calculated value?

The calculator caps the electrical output at the rated power. This reflects how real turbines stop increasing output after reaching their design limit.

7. Can this calculator estimate energy production too?

Yes. It converts power into hourly, daily, monthly, and yearly energy estimates. These values assume the same wind and operating conditions stay constant over that period.

8. Is this useful for small farms and large wind farms?

Yes. Use one turbine for a single machine estimate, or increase the turbine count for a farm-level result. It is a practical planning tool, not a full site simulation.