Figures from the American Wind Energy Association (AWEA) show installations dramatically down from 2012 when they hit record levels of 13.1GW.
The widely-expected fall was as a result of the expected expiration of the production tax credit (PTC) and Investment tax credit (ITC) subsidies.
While the government once again called time on the subsidy regime at the end of 2013, regulations were changed to allow projects under construction to qualify, as opposed to the previous stipulation that a wind farm must be completed.
This accounts for the spike in projects under construction at the end of the year, with work commenced on more than 12GW of developments, more than at any other time.
This compares with just 2GW under construction at the end of 2012.
There are now more than 90 projects under construction in 20 states. Texas leads the way with 7GW under way, well ahead of the next highest, Iowa, with 1.1GW.
The majority of installations were completed in the fourth quarter, with more than 1GW installed, compared with the first quarter when only 1.6GW was installed.
There is now 61.1GW of total installed wind capacity in the US.
