The National Electricity System (SEN) includes the following activities: generation; transmission; distribution; supply; market operations and logistics operation for switching of electricity suppliers, as stated in Decree-Law no. 29/2006 of the 15th of February.
The main activities of SEN can be described as follows:
- Generation: electricity is produced using various technologies and different primary sources of energy (coal, gas, fuel oil, diesel, water, wind and biomass, among others). In Portugal Mainland, electricity is produced by several distinct companies.
- Transmission: after generation, electricity must be transported at Very High Voltage level from the power plants to the supply points. In Portugal mainland, transmission is handled by a single company – Rede Eléctrica Nacional (REN).
- Distribution: in addition, electricity is distributed through High, Medium and Low Voltage levels through distribution networks where most of the end consumers are connected. In Portugal mainland most of the distribution networks are handled by one single company, EDP Distribuição, and also by some Low Voltage electricity distribution operators.
- Supply: electricity suppliers are responsible for managing the relations with the end customers, including billing and energy-related, advice and support. In Portugal, mainland electricity can be sold on the liberalized market, through free suppliers and on the regulated market, through the last resort supplier. Tariffs per activity.