Small Wind Guidebook/How Do I Choose the Best Site for My Wind Turbine

From Open Energy Information


How Do I Choose the Best Site for My Wind Turbine?

The farther you place your wind turbine from obstacles such as buildings or trees, the less turbulence you will encounter.

A proper site assessment is a detailed process that includes wind resource assessment and the evaluation of site characteristics. With this in mind, you may wish to consider hiring an experienced small wind site assessor who can determine your property’s optimal turbine location. The following information highlights key steps in the site selection/assessment process.

If the surrounding area of a potential site is not relatively flat for several miles, then an evaluation of the main topographic features is necessary, both nearby (macro siting) and at the proposed turbine site (micro siting). The topographical evaluation should include shape, height, length, width, and distance and direction away from the proposed turbine site of any landforms. “Nearby” could include influences from large objects such as hills, groves of trees, or high wind breaks up to a mile away, and smaller objects could include single trees and buildings, especially within 500 feet of the proposed turbine location.

Owners of projects located near complex terrain should take care in selecting the installation site. Landforms (or orography) can influence wind speed, which affects the amount of electricity that a wind turbine can generate. Elevated areas not only experience increased wind speeds because of their increased height in the wind profile but also may cause local acceleration of the wind speed, depending on the size and shape of the landform. If you site your wind turbine on the top of or on the windy side of a hill, for example, you will have more access to prevailing winds than in a gully or on the leeward (sheltered) side of a hill on the same property. Other elevated landforms (bluffs, cliffs) can create turbulence, including back eddies, as the wind passes up and over them. Siting the tower to avoid the zones of turbulence created by the landform is critical.

Turbulence intensity is a major issue for small turbines because of their tower height and location around “ground clutter.” Turbulence can reduce the annual energy output estimate from 15% to 25% because wind turbine power curves are typically developed based on measurements taken at sites with relatively low turbulence intensity compared to typical small wind project sites.

Varied wind resources can exist within the same property. In addition to measuring or finding the annual wind speeds, you need to know about the prevailing directions of the wind at your site. Knowing the prevailing wind direction(s) is essential to determining the impact of obstacles and landforms when seeking the best available site location and estimating the wind resource at that location. To help with this process, small wind site assessors typically develop a wind rose, which shows the wind direction distributions of a given area. The wind rose divides a compass into sectors (usually 8 or 16) and indicates the average wind speed, average percentage of time that the wind blows from each direction, and/or the percentage of energy in the wind by sector. Wind roses can be generated based on annual average wind speeds, or by season, month, or even time of day as needed.[1]

In addition to geologic formations, you need to consider existing obstacles such as trees, houses, and sheds, and you need to plan for future obstructions such as new buildings or trees that have not reached their full height.[2] Your turbine needs to be sited upwind of buildings and trees[3], and it needs to be 30 feet above anything within a 500-foot horizontal radius.[4] You also need enough room to raise and lower the tower for maintenance, and if your tower is guyed, you must allow room for the guy wires.

Whether the system is stand-alone or grid-connected, you also need to consider the length of the wire run between the turbine and the load (house, batteries, water pumps, etc.). A substantial amount of electricity can be lost as a result of the wire resistance—the longer the wire run, the more electricity is lost. Using more or larger wire will also increase your installation cost. Your wire run losses are greater when you have direct current (DC) instead of alternating current (AC). So, if you have a long wire run, it is advisable to invert DC to AC.[5]

You may wish to consider hiring an experienced small wind site assessor who can determine where the turbine should be located on your property.

Wind Turbines Mounted on Buildings

The number of small wind turbines mounted on rooftops has increased in recent years. It should be noted that all wind turbines vibrate and transmit the vibration to the structure on which they are mounted. This can lead to noise problems within the building, and the wind resource on the rooftop is in an area of increased turbulence, which can shorten the life of the turbine and reduce energy production. Additional costs related to mitigating these concerns can lead to increased payback periods and total cost of the installation. For more information on the state of the rooftop wind turbine industry, see The Built-Environment Wind Turbine Roadmap.


  1.  "National Renewable Energy Laboratory. (2015). Small Wind Site Assessment Guidelines"
  2.  "U.S. Department of Energy. Installing and Maintaining a Small Wind Electric System"
  3.  "American Planning Association. (2011) Planning for Wind Energy"
  4.  "National Renewable Energy Laboratory. (2015). Small Wind Site Assessment Guidelines"
  5.  "U.S. Department of Energy. Installing and Maintaining a Small Wind Electric System"