Enter your wind speed, rotor diameter, air density, and turbine efficiency to calculate the theoretical wind power and actual available power output. Results include power in watts, kilowatts, and a visual breakdown of theoretical vs. usable energy.
Actual Power Output
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Theoretical Wind Power
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Actual Power Output
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Rotor Swept Area
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Wind Energy (Duration)
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Betz Limit Power (59.3%)
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Wind power is calculated using the formula P = ½ × ρ × A × v³, where ρ is air density (kg/m³), A is the rotor swept area (m²), and v is wind speed (m/s). The actual usable power is further multiplied by the turbine's efficiency factor (ξ), giving Pa = ξ × ½ × ρ × A × v³.
Wind power is proportional to the cube of wind speed (v³). This means a 20% increase in wind velocity results in roughly a 73% increase in power generation. Doubling wind speed increases power output by a factor of 8, making wind speed by far the most influential variable.
The Betz limit, approximately 59.3%, is the theoretical maximum fraction of wind energy that any turbine can extract. No real turbine can exceed this value due to the physical requirement that the air behind the rotor must still be moving. Practical turbines typically achieve 30–45% efficiency.
Horizontal-axis wind turbines (HAWT) rotate around a horizontal axis and are the most common type — both onshore and offshore. Vertical-axis wind turbines (VAWT) rotate around a vertical axis and can capture wind from any direction without yawing, making them useful in turbulent urban environments. HAWTs are generally more efficient at larger scales.
Air density directly multiplies into the power formula, so denser air produces more power at the same wind speed. Air density decreases at higher altitudes and higher temperatures. Standard sea-level density is 1.225 kg/m³ at 15°C; at high elevations or in hot climates, you should use a lower value for accurate results.
A typical household in the US uses around 10,500 kWh per year, or roughly 1.2 kW average power. A small wind turbine with a rotor diameter of 3–5 metres at moderate wind speeds (6–9 m/s) can produce 1–5 kW, which may be sufficient. Actual sizing depends heavily on your local average wind speed and turbine efficiency.
Energy production depends on turbine size, local wind speed, and efficiency. A 1 kW turbine running at rated power for 24 hours produces 24 kWh/day, but turbines rarely run at full capacity continuously. Using average wind speeds and a capacity factor of 25–40% gives a more realistic estimate for planning purposes.
The swept area is the circular area traced by the rotating blades, calculated as A = π × (D/2)², where D is the rotor diameter. A larger swept area intercepts more wind and therefore produces more power. Doubling the rotor diameter quadruples the swept area and thus the potential power output.