Wind Turbine: Power | Nominal Power | Yield | Annual Yield | Rotation | Magnitude | Distance | Repowering | Wind Site Factor
Wind Turbine Site Factor
Wind turbine site calculator for balcony wind turbines and small wind turbines based on installation location and surroundings.
The site factor describes how favorable the wind conditions are at a particular location. A value of 100 percent represents a very good reference site, while lower values are often to be expected for small wind turbines. The calculator considers only the micro-location, i.e. the local wind exposure and turbulence at the installation site, but not the general wind frequency and wind speed of the region. These can differ considerably between low-wind inland areas and windy coastal or mountainous regions.
This calculator is particularly suitable for small wind turbines installed on rooftops, balconies, or in built-up urban areas. It helps estimate local wind conditions, wind shadowing and turbulence, as well as the expected wind yield. Large wind turbines are usually planned using extensive wind measurements and flow simulations, whereas local conditions for small wind turbines often have to be estimated. Therefore, the calculator does not provide exact values, but rather a practical estimate of the expected wind conditions. The factors used are based on practical experience in wind engineering and have not been scientifically validated. The result can serve as an indication of site quality, but should not be interpreted as an exact value that will be achieved in practice. The site factor is only one of several indicators for whether installing a particular wind turbine is worthwhile. Other important considerations include public acceptance and, of course, cost.
Value tables
These are the factors used internally by the wind turbine site calculator. All values are estimates and should not be regarded as exact. The calculation is simply the multiplication of the individual factors and 100 percent.
| Installation site | Factor |
|---|---|
| Free-standing mast | 1.00 |
| Ground-level installation | 0.95 |
| Rooftop | 0.90 |
| Roof edge | 1.00 |
| Balcony | 0.65 |
| Courtyard | 0.35 |
| Height relative to roof edge | Factor |
| 1 to 2 m above | 1.05 |
| At roof edge level | 1.00 |
| More than 2 m below | 0.85 |
| Wind exposure | Factor |
| 360° | 1.00 |
| 270° | 0.93 |
| 180° | 0.85 |
| 90° | 0.70 |
| 45° | 0.50 |
| Prevailing wind direction | Factor |
| Facing prevailing winds | 1.00 |
| Side to prevailing winds | 0.80 |
| Opposite prevailing winds | 0.60 |
| Distance to wall | Factor |
| Free exposure (> 2 m distance) | 1.00 |
| Near a wall (0.5 - 2 m) | 0.85 |
| Directly at a wall or railing (< 0.5 m) | 0.75 |
| Surroundings | Factor |
| Open terrain | 1.00 |
| Suburban area | 0.90 |
| Urban area | 0.80 |
| Dense high-rise buildings | 0.60 |
| Building corner | Factor |
| Exposed building corner | 1.10 |
| Near a building corner | 1.05 |
| No special position | 1.00 |
The installation site describes the general location of the wind turbine. Free-standing masts usually offer the best wind conditions. Balconies and courtyards are often shielded by buildings and experience stronger turbulence. Wind turbines on rooftops or roof edges often benefit from higher wind speeds.
The height relative to the roof edge plays an important role, as wind above obstacles is usually stronger and more uniform. Wind turbines below the roof edge are often located in the wind shadow of the building.
Wind exposure describes the angular range from which the wind can reach the turbine without major obstacles.
The prevailing wind direction describes the orientation of the wind turbine relative to the dominant winds. In much of Europe, the prevailing winds often come from the west.
The distance to the wall affects the airflow in the immediate vicinity of the wind turbine. Walls, railings and facades often create vortices and turbulence that can reduce the usable wind power.
The surroundings also have a major influence on wind conditions. In open terrain, wind is usually stronger and more uniform than in cities or between high-rise buildings. Buildings, trees and other obstacles slow down the wind.
Building corners play a special role. Wind can be locally accelerated there as the airflow is deflected around the building. At the same time, turbulence often increases. Therefore, elevated site factors near building corners should only be regarded as approximate values.
Example of a small wind turbine on a high-rise building in Munich. For the location shown at the southwest corner of a high-rise building at about half the building height, this calculator estimates factors of balcony (0.65), more than 2 m below the roof edge (0.85), wind exposure of about 270° (0.93), facing prevailing winds (1.00), near a wall (0.85), urban surroundings (0.80), and an exposed building corner (1.10). This results in an estimated site factor of 38.4 %.
Last updated on 06/14/2026. Author: Jürgen Kummer
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