Addressing the St. Petersburg International Economic Forum, German Gref said the agreement was of key importance for Russian electricity monopoly Unified Energy System, which controls HydroOGK.
Vyacheslav Sinyugin, CEO of HydroOGK, a hydropower wholesale generating company, said the two companies would set up a managing company on a parity basis before the end of the year.
Sun Group is currently involved in joint projects with Itera, Russia's largest independent natural gas producer. A joint venture of Itera and Sun Group is taking part in the construction of a terminal for liquefied natural gas in the state of Gujarat, western India.
Two other Russian companies are currently developing India's electric power sector. Technopromexport is building thermal power plants, and Atomstroyexport is developing nuclear power stations.