Wind Turbine Output Calculator

Most home wind turbines are a mathematical illusion. Use the exact physics equation to calculate how much power your turbine will actually generate based on size and wind speed.

Standard baseline: 5 m/s (11 mph). Strong breeze: 8 m/s (18 mph).

2.5m

The physical width of the spinning blades. (1m = ~3.2ft)

35%

Includes aerodynamic limit (Betz) + generator loss. Keep around 30-40%.

For engineering estimation only. Wind does not blow consistently 24/7. Real-world daily output usually adheres to a Weibull probability distribution curve.

Output Telemetry

Target Output
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The Roof-Mount Myth: Why Small Wind Turbines Usually Fail

One of the most common mistakes in the DIY renewable energy community is buying a small 1-meter "400W" wind turbine from Amazon, mounting it to the roof of a suburban house, and expecting it to power a refrigerator. It will not work. In fact, it often won't generate enough electricity to charge a cell phone. Our Wind Turbine Output Calculator uses pure physics to reveal exactly why.

The Mathematical Formula

To calculate raw wind power, mechanical engineers use this strict equation:

Power (Watts) = 0.5 × Air Density × Swept Area × (Wind Speed)³ × Efficiency
  • •The Cubic Law of Wind: Notice that wind speed is cubed. This is the most important rule in wind energy. If wind speed drops from 8 m/s to 4 m/s (a 50% drop), the power output doesn't drop by half—it drops by a factor of 8. Small breezes generate mathematically zero power.
  • •Swept Area is King: The size of the circle your blades make determines how much wind you can physically "catch." A 1-meter turbine has an area of 0.78 m². A 3-meter turbine has an area of 7.06 m² (nearly 10x the energy capture potential). Tiny blades are physically incapable of capturing high wattage.

The Betz Limit (Why 100% Efficiency is Impossible)

You might wonder why you can't just set the efficiency slider to 100%. In 1919, physicist Albert Betz proved that a wind turbine can only possibly capture 59.3% of the kinetic energy in the wind. If it captured 100%, the air would completely stop behind the turbine, creating a vacuum that blocks new wind from entering. When you factor in the friction of the generator and wiring, a highly efficient real-world turbine peaks around 35% to 40%.

When Should You Use Wind?

Wind energy is fantastic, but it requires two things: Height and Open Space. Trees and houses create "turbulent air" that ruins efficiency. You must mount turbines on a 30ft+ tower in a wide-open area. If you live in the suburbs or are building a camper van, skip the wind turbine entirely. Plug your numbers into our Solar System Sizing Calculator instead. If you are building a true off-grid cabin with lots of land, check out our Off-Grid Power Estimator to calculate exactly how many batteries you need to store that sweet wind energy!

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Frequently Asked Questions

Why did the output drop so much when I lowered wind speed?

Because of the Cubic Law of Wind. Wind power does not scale linearly. If the wind speed doubles, the power output increases by 8 times. Conversely, if it halves, you lose almost all of your power generation.

Is a roof-mounted wind turbine a good idea?

For 99% of suburban homes, no. Houses, trees, and fences create 'turbulent air' which drastically reduces turbine efficiency. To get clean, 'laminar' wind flow, the turbine must be mounted on a tall tower well above any surrounding obstacles.

What is a good average wind speed for a turbine?

Most residential wind turbines require a minimum starting wind speed (cut-in speed) of 3 to 4 m/s (7-9 mph) just to start spinning. To actually generate meaningful, cost-effective power, you want an average sustained wind speed of at least 5.5 to 6.5 m/s (12-14 mph).

Does the number of blades matter?

More blades do not mean more power. In fact, large commercial turbines use 3 blades because it represents the optimal aerodynamic balance between capturing wind and minimizing drag. The 'swept area' (diameter) is far more important than the blade count.