 It is one of the first private Greek companies ever to be involved in Renewable Energy Sources and has been licensed for more than 600 MW.Terna is involved in power generation from thermal units through its subsidiary Heron S.A., which is licensed for the construction and operation of thermoelectric power stations fuelled with natural gas.Heron owns and operates a 147 MW gas fired power plant in Viotia which is designed to cover the system's reserve needs, as well as the needs in periods of high demand, over the following years.