Distribution grids ensure the transit of electricity between the national transmission grid and consumers: electricity conveyed over long distances by the transmission grid at extra-high voltage (EHV) is then delivered to substations from the distribution grid,  in order to convey it over shorter distances at high, medium and low voltage (HV, MV and LV) to consumers’ premises.

Distribution system operators (DSOs) are responsible for managing, operating and maintaining the grid, extending it to new supply locations and maintaining the lines, transformer stations and ancillary facilities and ensuring the quality of service provided. As electricity consumption at different voltage levels varies over time, grids must be prepared for its fluctuations at each branch. The distribution networks should likewise be prepared to the connection of a large variety of distributed generation.

DSO can contract flexibility services, particularly for managing congestion in their areas, in order to increase the operating efficiency and development of the distribution network. In particular, DSO may contract these services to distributed generation providers, consumers or energy storage.

The existence of smart metering systems allows DSO the observability of their networks and the reduction of their operational and maintenance costs

DSOs only interact with consumers on issues such as grid connections, meter readings and technical quality of service.

Distribution system operators

On HV, MV and LV grids:

Exclusively on LV grids:

Every two years, each DSO, together with the transmission system operator (TSO), draws up a 5-year investment plan: the Five-Year Development and Investment Plan for Distribution Grids (PDIRD-E). This Plan is subject to public consultation and to an opinion from ERSE and the Directorate-General for Energy and Geology, and is approved by the Government, after being discussed in Parliament.

ERSE is responsible for the economic regulation of the electricity distribution activity, setting the tariffs for the use of the distribution grid and operators’ revenues.

To find out more about this, have a look at the pedagogical guide Electricity: how does it work?

Compliance Programme

The Distribution System Operator (DSO) serving 100 000 or more customers is required to implement legal, functional and accounting unbundling. In this context, it must establish a Compliance Committee which, under the applicable European and national rules, must submit to ERSE a Compliance Programme that sets out the measures adopted to ensure that discriminatory behaviours are excluded and that their fulfilment is adequately monitored, setting out the obligations of employees to achieve that goal.

The E-REDES Compliance Committee proposes to ERSE, on an annual basis, the approval of the Compliance Programme, which is analysed by ERSE. The Programme and its assessment are published on the DSO and ERSE website.

In addition, a report accompanying the implementation of the Compliance Programme is submitted every year and is also published on the same websites.


ERSE’s final decision on the  Compliance Programme for 2023

Response from the Compliance Committee, amending the draft Compliance Programme for 2023

ERSE’s analysis of E-Redes’ draft Compliance Programme for 2023

E-Redes Draft Compliance Programme for 2023 

2021 Compliance Report (submitted in March 2022

2022 Compliance Report (submitted in March 2023)

Low-voltage distribution

Low-voltage (LV) electricity distribution in mainland Portugal is assigned to municipalities, which are entitled to grant concessions for the activity or directly operate the distribution grid (involving transformer stations, power lines and cables that feed the electrical installations of households and small businesses).

At present, all 278 municipalities have granted concessions for this activity, and there are 11 LV grid concessionary operators, of which EDP Distribuição-Energia is the largest, with around 99.5% of customers. The current municipal concession contracts have uneven terms, ending in 2026, with the majority ending between 2021 and 2022.

Concessions for the distribution of low-voltage electricity are awarded by each municipality or association of municipalities, following a public tender [Decree-Law Nº 15/2022, of 14 January], on the basis of a standard contract approved by the Government, having heard the National Association of Portuguese Municipalities (ANMP) and ERSE.

The rules for the organisation of calls for tenders for the award of LV concessions were approved by Law No 31/2017, of 31 May,. That law and the subsequent Resolution of the Council of Ministers No 5/2018, of 11 January, defined the programme of studies and actions to be developed by ERSE, in collaboration with the Directorate-General of Energy and Geology and ANMP, originating the creation of a working group under the terms of Despacho nº. 11814/2020, of 30 November.

Portaria No. 397/2023, of November 28, the result of that working group, regulates the standard parts for the public tender procedure for the award of low voltage electricity distribution concessions in the Portuguese mainland..

As part of this work, ERSE provides general and more specialised information on the distribution activity of LV and current concessions, as well as information on the procedure for awarding new concessions and on studies and proposals provided for in the law and sent to the Government.


  • Guide - Low voltage electricity distribution (e-book)
  • Booklet - Quality of Service and Electricity Grid Operators (e-book)
  • Guide - Characteristics of LV electricity distribution grids in mainland Portugal (e-book)
  • Characterisation data of the LV grid according to municipality (excel)
  • Seminars on tenders for the concession of low voltage electricity distribution (Coimbra, Lisboa, Évora, Guimarães, Portimão – 2018) – ERSE Presentation
  • Definition of territorial areas of tenders - ERSE Proposal (in the scope of article 5 of Law No 31/2017, of 31 May)
  • Standard documents for procedures - ERSE Study (within the scope of paragraph 2 of RCM No 5/2018, of 11 January)