The Small Wind Turbine study found the sales of small turbines, used primarily to power homes, farms, and small businesses, rose by 15% in 2009. Overall this equates to an extra 20.3MW.
It is also estimated that 100,000 small wind turbines have been installed in the country, raising the capacity above the 100MW milestone.
AWEA manager of small systems and author of the report, Ron Stimmel, said federal and state incentives had made small turbines more affordable.
He added: "The US small wind turbine market is by far the world's largest, both in terms of installations and manufacturing."