Artikel 19

1.   From 5 August 2025, the relevant regulatory authority shall ensure the transparency of the methodologies, parameters and values used to determine allowed or target revenue of transmission system operators. The regulatory authority shall publish the information referred to in Annex I, or shall require the publication by the relevant transmission system operator subject to the protection of data considered by the relevant regulatory authority to be commercially sensitive. That information shall be made available in a freely accessible, downloadable and read-only format and, to the extent possible, in one or more commonly understood languages.

2.   The costs of the transmission system operator shall be subject to an efficiency comparison between transmission system operators. ACER shall carry out that efficiency comparison. By 5 August 2027 and every four years thereafter, ACER shall publish a study comparing the efficiency of transmission system operators’ costs, subject to the protection of data considered by ACER to be commercially sensitive. The relevant regulatory authorities and the transmission system operators shall provide ACER with all the data necessary for that comparison. When periodically setting the allowed or target revenue of transmission system operators, the relevant regulatory authorities shall take into account such comparison and national circumstances.

3.   The relevant regulatory authorities shall assess the long-term evolution of transmission tariffs on the basis of the expected changes to their allowed or target revenue and in natural gas demand within the relevant regulatory period, and, where available until 2050. To conduct that assessment, the regulatory authority shall include the information about the strategy described in the integrated national energy and climate plan of the Member State concerned and the scenarios underpinning the ten-year network development plan as developed in accordance with Article 55 of Directive (EU) 2024/1788.