The ability to produce electricity is measured in watts. The output of a wind turbine is directly dependent on the turbine's size and the wind's speed via the rotor. Ranging from 250 watts to 5 megawatts (MW), wind turbines are now being manufactured with various power ratings.

Wind speed is the most important element in analyzing the turbine’s output. Primarily, a site's wind speed is measured together with other factors as part of a wind resource assessment before the construction of a wind farm. Usually, an annual average wind speed greater than four meters per second (4m/s), is essential for diminutive wind electric turbines (less wind is necessary for water-pumping operations, etc). Utility-scale wind power plants need minimum average wind speeds of 6 m/s (13 mph). Simply put, the amount of wind energy generated is directly reliable on the presence of the wind and its respective speed. In fact, wind speed is such a critical factor that doubling the wind speed increases the available power by a factor of eight. This is because the power available in the wind is proportional to the cube of its speed. Thus, a turbine operating at a site with an average wind speed of 12 mph could in theory generate about 33% more electricity than one at an 11 mph site, because the cube of 12 (1,768) is 33% larger than the cube of 11 (1,331).

The average U.S. family consumes about 10,655 kilowatt-hours (kWh) of electricity annually. To better provide an understanding of scale, one must know that electricity production and consumption are most commonly measured in kilowatt-hours (kWh). A kilowatt-hour means one kilowatt (1,000 watts) of electricity produced or consumed for one hour. As an example, one 40-watt light bulb left on for 25 hours consumes one kilowatt-hour of electricity (40 watts x 25 hours = 1,000 watt-hours = 1 kilowatt-hour). One megawatt of wind energy can produce anywhere from 2.4 to more than 3 million kWh every year. In coming up with this calculation it is important to realize that wind turbines are not constantly in use. Wind blows steadily at times, and not at all at other times. The measure of a turbine or a wind farm’s actual energy production versus the amount of power that would have been produced if the turbine operated at full capacity for the same amount of time is known as capacity factor. A wind farm will typically operate anywhere between a 25% to 35% capacity factor. Therefore, a wind turbine rated at one megawatt, operating at a 30% capacity factor would produce 1MW * 1000 = 1,000kW * 365 days/ year * 24 hours/ day * 0.30 = 2,628,000 kWh of electricity. Dividing, 2,628,000 kWh by 10,655 kWh (average annual US home power consumption), one comes up with approximately 246 homes powered annually. So, a megawatt of wind generates almost as much electricity for 225 to 300 households’ use. However, it is essential to consider that because wind does not blow at all times; it cannot be the only source of power for that many households. Some other form of energy generation or a storage system is required for a continuous supply of energy (typically, wind power storage is not required, as wind generators only make up a very minor part of the overall power generation facilities. Other fuel sources are utilized to put power onto the grid when the wind is not blowing)

The U.S. Department of Energy claims that no other backup is essential to maintain system dependability when wind is added to a utility system.