As of the beginning of 2019, 41 states had at least one installed wind turbine. Of these 41 states, Texas had the largest number of turbines, with more than 13,000, and the most installed wind capacity, at 24.2 gigawatts (GW). As wind technology has advanced, turbines have grown larger in the United States, and the capacity of individual turbines has increased with size. States where wind adoption occurred early, such as California, have a high number of turbines relative to their wind generation capacity compared with states where wind was adopted later, such as Texas, Iowa, Oklahoma, Kansas, and Illinois.
Based on data in the U.S. Energy Information Administration’s Annual Electric Generator Inventory, the earliest U.S. wind turbines still operating were installed in California in July 1975. Despite having the second most installed wind turbines, California accounts for only 6.1 GW of total installed capacity, fourth among the states. In 2018, California reduced its number of turbines but still increased its wind capacity by repowering some turbines to improve their efficiency.
Although California has the oldest operable turbine (44 years), Tennessee has, on average, the oldest operating wind turbines, with an average project age of 17 years. California, Wyoming, Minnesota, and Arkansas round out the top five states in terms of oldest project ages, from an average 16 years old in California to an average 12 years old in Arkansas.
Wind turbine hub heights have increased over time because turbine blades have gotten longer. Turbines with longer blades and a greater rotor diameter typically have higher nameplate capacity. Older turbines, such as those in California or Tennessee, generally are shorter and have shorter blades than newer turbines, which have higher hub heights to accommodate longer blades.