A wind energy system transforms the kinetic energy of moving air into mechanical or electrical energy.   These can be used to generate electricity for homes and businesses and for sale to utilities, as well as to perform tasks like propelling a sailboat or pumping water in rural or remote areas.

Wind is a proven, cost-effective, and domestic source of energy.  Once a wind project is operating, it produces virtually no greenhouse gas emissions, which contribute to global warming.

The United States displaces an estimated 23 million tons of carbon dioxide each year through wind power – an amount of carbon dioxide that otherwise would have been emitted if coal, natural gas, oil and other traditional energy sources were used to generate an equivalent amount of electricity.

In addition, wind energy is renewable. Wind is free and will blow as long as the Sun heats the Earth. Fossil fuels like oil, natural gas, and coal have a finite supply causing their costs to rise as supplies begin to decrease.

Wind energy could supply about 20% of the nation's electricity, according to Battelle Pacific Northwest Laboratory.  Wind resources in America are even greater, however.  If there was enough transmission capacity, North Dakota alone is theoretically capable of producing enough wind-generated power to meet more than one-quarter of the electricity demand of the entire country.

Wind power generating capacity increased by 27% in 2006 and is expected to increase an additional 26% in 2007, according to the American Wind Energy Association.  The U.S. wind energy industry installed 2,454 MW of new generating capacity in 2006, an investment of approximately $4 billion, making wind one of the largest sources of new power generation in the country — second only to natural gas.

This growth in new wind farms increased the country’s installed wind energy capacity to 11,603 MW.  Currently installed U.S. wind facilities will produce an estimated 31 billion kilowatt-hours annually, or enough electricity to serve 2.9 million American homes.

The generation of electricity is measured in watts and other larger increments, such as kilowatts (kW, 1,000 watts), megawatts (MW, 1 million watts), and gigawatt (GW, 1 billion watts).  Electricity production and consumption typically are measured in kilowatt-hours (kWh).  A kilowatt-hour means one kilowatt (1,000 watts) of electricity produced or consumed for one hour.  For example, a 100-watt light bulb left on for 10 hours consumes one kilowatt-hour of electricity.

The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor.  Wind turbines being manufactured now have power ratings ranging from 250 watts to 5 MW.

For example, a 10 kW wind turbine can generate about 10,000 kWh annually at a site with wind speeds averaging 12 miles per hour, or about enough to power a typical household. A 5 MW turbine can produce more than 15 million kWh in a year – enough to power more than 1,400 households.

An average U.S. household uses about 10,655 kilowatt-hours (kWh) of electricity each year.  One megawatt of wind energy can generate between 2.4 to 3 million kWh annually.  Therefore, a megawatt of wind generates about as much electricity as 225 to 300 households use.  But because the wind does not blow all of the time, it cannot be the only power source for those households, unless a storage system is present.  The term "number of homes served" simply helps explain a quantity of electricity in an understandable way.

Utility-scale wind turbines for land-based wind farms come in various sizes, with rotor diameters ranging from about 50 meters to about 90 meters, and with towers of roughly the same size. A 90-meter machine with a 90-meter tower would have a total height from the tower base to the tip of the rotor of approximately 135 meters (442 feet). Offshore turbine designs now under development will have even larger rotors – 110 meter rotors or larger.

Wind turbines intended for residential or small business use are much smaller. Most of these have rotor diameters of 8 meters or less and would be mounted on towers of 40 meters in height or less.