 The 12 south side main generators are also in operation . No. 22 began operation on June 11 , 2007 and No. 15 started up on October 30 , 2008 . The sixth ( No. 17 ) began operation on December 18 , 2007 , raising capacity to 14 @.@ 1 GW , finally surpassing Itaipu ( 14 @.@ 0 GW ) , to become the world 's largest hydro power plant by capacity . 
