In 2005, five thermal power plants with installed capacity about 8,700 MW were merged into single company. The power output of these plants in 2007 was around 48 TWh.
In April 2010, Gazprom, the major shareholder of OGK-2 and OGK-6, announced a plan to merge these companies. OGK-2 issued 26.59 billion new shares (81.2% of existing share capital) which were used for conversion of OGK-6 shares at a ratio of 1.2141 OGK-6 to 1 OGK-2 share. The merger was completed by 1 November 2011.