RES Americas adds 44 MW to Washington wind farm

* Adds 44 megawatts to wind project; total capacity 273 MW

* Used 22 wind turbines made by Vestas in expansion

LOS ANGELES Nov 12 (Reuters) - Renewable Energy Systems Americas Inc has finished the expansion of a wind farm in the U.S. Northwest, adding 44 megawatts for a total of 273 MW, the privately held wind power developer said on Thursday.

RES Americas said it used turbines from Vestas Wind Systems A/S (VWS.CO), the leading turbine maker, for the expansion of the Wild Horse Wind Facility in Kittitas County, Washington.

Wind has been a fast-growing source of power generation, although expansion slowed partly due to the credit crisis. The United States is on track to add about 6,000 MW in wind power this year, down nearly 30 percent from last year, according to the American Wind Energy Association.

Based in Broomfield, Colorado, RES Americas develops and builds renewable energy projects and has more than 12.5 gigawatts of projects under development.

The company, which says it has built about a seventh of all the installed U.S. wind power, said the extra turbines at Wild Horse will power an additional 11,800 homes, giving the farm overall capacity to power as many as 70,000 households. (Reporting by Laura Isensee; editing by Braden Reddall and Andre Grenon)