The liberalization of the natural gas market began in 2007, and, as of January 2010, all consumers (domestic and non-domestic) have the right to choose their natural gas supplier.

In 2007, the process of termination of regulated end user tariffs for natural gas began and transitional end user tariffs started to apply. This termination process had the following schedule:

• July 2010: consumers with an annual consumption of natural gas greater than10 000 m³
• July 2013: consumers with an annual consumption of natural gas greater than 500 m³ and lower than 10 000 m³
• January 2013: consumers with an annual consumption of natural gas below, or equal to 500 m³

Suppliers of last resort (SLR) started applying the transitional end user tariffs to natural gas consumers who are still being supplied on a regulated market basis and have not chosen a new supplier. These tariffs are expected to apply until 31 December 2025, when the transitional period ends (Administrative Rule No 83/2020, of 1 April).

Economically vulnerable customers maintain access to the regulated end customer tariff and to applicable social discounts.

Retail market

As part of the activity of following up and monitoring the retail natural gas market, ERSE collects information on natural gas prices (Order No 3677/2011, of 24 February), namely:

• Prices of commercial offers (reference prices), made available by the various suppliers
• Invoiced prices, which are sent to ERSE every quarter by all suppliers in the natural gas market (free suppliers and regulated suppliers)

The prices of commercial offers are disclosed by ERSE through the Commercial Offers Newsletters and the energy price simulator, which help consumers choose their supplier.

ERSE publishes the Liberalised Market Newsletter on the liberalised market, which includes various matters, namely those relating to the evolution of the liberalised market, market shares, the intensity of supplier switching, the structure of switching or market concentration.

ERSE publishes an annual report  with an analysis of the electricity and natural gas retail markets in Portugal, including detailed information from an annual perspective and considering the medium and long-term evolution.