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U.S. Department of Energy Energy Efficiency and Renewable Energy

Wind Turbines

Wind turbines capture the kinetic energy in the wind using propeller-like blades mounted on a shaft. When the wind makes the blades turn, the shaft spins a generator to produce electricity. Small wind turbines can be used to pump water or provide power to a home, for example, while larger turbines can be used to a power an entire community or to provide power to the electricity grid.

Today's wind turbines are much more efficient than the windmills of the past. They have fewer blades, usually two or three, that are aerodynamically designed to capture the most energy from the wind. As wind speeds increase, the amount of electricity generated increases proportional to the cube of the wind speed, so small increases in wind speed yield large increases in available power. Because faster, less turbulent winds are found higher off the ground, new utility-scale wind turbines are normally placed on towers at least a hundred feet tall.

Photo of a midwest farm with wind turbines.

Wind turbines easily coexist with farming activities.

Wind-generated electricity is the least expensive form of renewable power, and is becoming one of the cheapest forms of electricity — from any source. In some locations, the cost of electricity from wind is comparable to that from conventional fossil-fueled power plants. Wind turbines generate electricity wherever the wind blows, and they add value to land without interfering with other uses such as cattle grazing or farming. Installing a small, stand-alone wind turbine is often far less expensive than extending a power line to a remote area, which can easily cost $10,000 per mile.

Unlike traditional power sources, however, the wind is intermittent. Stand-alone wind turbines (i.e., those not connected to the electricity grid) must use an on-site, backup power system for when the wind stops blowing. This could be as simple as a bank of batteries that are charged by the turbine, or a more complicated (and expensive) hybrid power system incorporating solar panels and a backup generator to provide additional battery-charging capacity and auxiliary power.

See the following links for more information:

General Wind Information

Wind Resource Maps

Estimates of the wind resource are expressed in wind power classes ranging from Class 1 (the lowest) to Class 7 (the highest). Each class represents a range of mean wind power density or equivalent mean wind speed at specified heights above the ground. Modern utility-scale wind turbines typically require Class 4 or stronger winds, while some smaller turbines (below about 100 kW in capacity) can operate economically in areas with Class 2-3 wind resources, allowing them to provide power to more remote sites where the cost of electricity is higher. Areas designated as Class 1 are generally unsuitable for wind energy development.

The wind resource maps will give you a general idea about mean wind speeds and power in your area. If you want to obtain a more precise picture of your wind resource, you can measure wind speeds at your location using a recording anemometer. The most accurate readings are taken at "hub height" (the elevation at the top of the wind turbine tower). This requires placing the anemometer high enough to avoid turbulence created by trees, buildings, and other obstructions.

Map of the United States showing wind strength patterns. The highest wind speeds are typically in mountain ranges, along ridge lines in low-lying areas, and some coastal areas.

Note: If you cannot access the content of this map due to a disability, please contact the webmaster.

Project Development

Wind energy is one of the most cost-competitive renewable energy technologies. New, utility-scale wind projects are being built in the United States today with energy costs as low as 4 cents/kWh at better wind sites, such as Class 6. Wind energy at Class 4 sites is currently marketed at prices in the 5 cents/kWh to 7 cents/kWh range. Electricity generated by small-scale wind turbines is significantly more expensive; with Class 5 winds, the cost of electricity from these systems is generally in the range of 10 cents/kWh to 15 cents/kWh.

The following resources can help you determine the likely cost of electricity from your proposed wind project and to evaluate the other financial and environmental aspects of wind power installations.

Photo of a large scale GE-3.6MW Wind Turbine

This 3.6-megawatt wind turbine is one of the largest prototypes erected to date. Units larger than 4 megawatts in capacity are now under development.

Large-Scale Wind Turbines

Navajo utility workers installing a 400-watt wind turbine next to an 880-watt solar array.

Navajo utility workers installing a 400-watt wind turbine next to an 880-watt solar array. (Photo: Larry Ahasteen)

Small-Scale Wind Turbines

  • Small wind electric systems — This DOE Web site provides some excellent information.

  • Small wind systems — Includes a list of small wind manufacturers, information on permitting, an introduction to issues affecting residential installations, and state-specific guides to buying and installing a small wind turbine. Provided by AWEA.

  • Small wind for homeowners, ranchers, and small businesses — Part of the Wind Powering America site, this Web page provides a variety of information about small-scale wind power installations, including Small Wind Electric Systems: A U.S. Consumer's Guide (PDF 1.2 MB). Download Adobe Reader.

  • Evaluating State Markets for Residential Wind Systems (PDF 812 KB) — This 102-page report examines the break-even costs and simple payback times for small wind turbines in each state, for different wind resource classes and accounting for a variety of incentives. It can be a useful resource for evaluating the economics of small wind turbine installations. Download Adobe Reader.