The rise in installed capacity has been attributed to the uncertainty surrounding the future of the Production Tax Credit (PTC), which is set to expire at the end of the year.
Over 8.3GW of new capacity is under construction as developers attempt to bring projects online before the PTC expires.
AWEA, which released the figures, called on the government to extend the PTC before the end of the year.
AWEA CEO Denise Bode said: "It is urgent Congress extends the PTC now, before the end of the first quarter or risk losing a new manufacturing centre to foreign countries."
Vestas has already threatened to cut 1,600 jobs in the US if the PTC is not renewed.
Earlier this week, Iberdrola Renewables, America's second-largest wind developer, announced it was laying off 50 people in the US. While in October, EDP Renewables cut 10% of its US workforce.