Wind Turbine Output Calculator
Estimate energy output from a wind turbine using rotor size and wind speed.
Please note: An estimate based on the figures you entered. Real-world results vary with conditions this calculation cannot see, so treat it as a starting point rather than a final answer.
What the Wind Turbine Output Calculator does
Wind power depends on air density, swept rotor area and the cube of wind speed. That cubic relationship is why site selection matters more than turbine choice — doubling wind speed produces eight times the power from the same machine.
Formula
Swept area = π × (Rotor diameter ÷ 2)²Power = ½ × Air density × Swept area × Wind speed³ × Power coefficientAnnual kWh = Average power ÷ 1,000 × 24 × 365Betz limit: no turbine can exceed a power coefficient of 0.593
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| Turbine specified by | one of 2 options | Yes | — |
| Rotor diameter | m | In some modes | Accepts more than 0. Shown Turbine specified by is Rotor diameter. |
| Rated power | kW | In some modes | Accepts more than 0. Shown Turbine specified by is Rated power. |
| Average wind speed | m/s | Yes | 5 m/s is modest; 7+ m/s is a strong site. Accepts more than 0. |
| Power coefficient | % | In some modes | Turbine efficiency. The Betz limit is 59.3%; real turbines reach 35–45%. Shown Turbine specified by is Rotor diameter. |
| Air density | kg/m³ | In some modes | Accepts 0.1 or more. Shown Turbine specified by is Rotor diameter. |
| Capacity factor | % | In some modes | Share of rated output achieved over a year. Shown Turbine specified by is Rated power. |
| Electricity rate per kWh | selected currency | Optional | Accepts 0 or more. |
| Currency | one of 10 options | Optional | — |
How to use it
- Choose Turbine specified by and Currency.
- Enter Average wind speed.
- Fill in the remaining inputs the form shows for your choice.
- Optionally add Electricity rate per kWh.
- Select Calculate.
Worked example
A 3 m rotor at 5.5 m/s average wind, 35% power coefficient, air density 1.225 kg/m³.
- Rotor
- 3 m
- Wind
- 5.5 m/s
- Cp
- 35
- Density
- 1.225
Swept area 7.07 m². Power = 0.5 × 1.225 × 7.07 × 166.4 × 0.35 = 252 W, giving about 2,209 kWh a year.
Frequently asked questions
What is the Betz limit?
The theoretical maximum share of wind energy a turbine can extract — 59.3%. Taking more would require stopping the air completely, which would prevent further air passing through.
Is small-scale wind worth it?
Only on genuinely windy, unobstructed sites. Below about 5 m/s average, solar almost always delivers more energy per unit of investment.