E-CO is the second largest power producer in Norway. E-CO is owned by the municipality of Oslo. The core business of E-CO is ownership, management and development of hydropower plants and business development.

E-CO owns and manages wholly or partially more than 60 power plants in southern Norway. E-CO has an average annual power production of 9.7 TWh. Production capacity is approximately 2,800 MW.
E-CO has owner's shares in Oppland Energi AS, Opplandskraft DA, Vinstra Kraftselskap DA, Embretsfosskraftverkene DA og Norsk Grønnkraft AS.