The US managed to install 13,131MW in 2012 and the decrease is being blamed on the threat of the production tax credit (PTC) expiring.
The PTC was renewed at the last minute in January 2013, but the supply chain had already slowed, causing the slump on new installations last year.
At the end of 2013, 12GW and 100 projects were under construction, which should boost installations this year, but AWEA warns that the boom-bust pattern is set to continue if the uncertainty surrounding the PTC and policy continues.
AWEA chief executive Tom Kiernan said: "The time is now for Congress to give the industry a green light to keep contributing jobs and clean electrons to America, by providing a stable business environment for further investment."
At the start of April, the US Senate finance committee approved a package of tax breaks, including a two-year extension on the PTC for wind energy, but the bill is still waiting for Senate approval.
The AWEA report stated: "The US industry ended 2013 with 61,110MW operating in the US across 46,100 wind turbines in 39 states and Puerto Rico.
"The 905 utility-scale wind projects operating here exceed 4% of the US electricity generation during 2013, and are now able to power the equivalent of 15.5 million homes."
