The 16 Gamesa 850kW turbines will be commissioned in October, KenGen said.
KenGen will also commission a 6.8MW plant built nearby by Belgium's TPF Econoler and equipped with Vestas 850kW turbines.
Although it was finished in March, the facility has been on hold, waiting for the transmission company to complete the substation and grid connection.
The two plant will boost Kenya's installed wind capacity from 5.1MW, operating at Ngong Hills since 2009, to 25.5MW.
In the meantime, a 61MW project to be built at Kinangop, north of Nairobi, has been delayed because of protests by local villagers over compensation agreements.