The European Union Agency for the Cooperation of Energy Regulators (ACER) has approved the fourth amendment to the day-ahead capacity calculation methodology for the Core capacity calculation region, in a decision dated 16 July 2026 and published on 17 July 2026. The decision follows a referral by the Core regulatory authorities, who could not reach agreement on the proposal submitted by transmission system operators (TSOs) in November 2025.
The Core region's day-ahead capacity calculation methodology was originally approved by ACER Decision 02/2019 of 21 February 2019, after Core regulatory authorities failed to agree on the initial TSO proposal. Since then, the methodology has undergone several amendments developed by Core TSOs and approved by the Core regulatory authorities. The latest amendment proposal was submitted by Core TSOs in November 2025 to the Core regulatory authorities. As the authorities could not agree, they referred the matter to ACER on 30 March 2026, under Articles 9(5), 9(7)(a), (11) and (13) of the CACM Regulation (EU 2015/1222).
ACER's decision sets out the amended proposal in Annex I and provides a consolidated version of the methodology in Annex II. The amendment aims to improve the coordinated calculation of cross-zonal capacity in the day-ahead timeframe, which is essential for efficient cross-border electricity trading and congestion management in the Core region, covering central and western European countries.
The decision impacts transmission system operators, who must implement the amended methodology, and national regulatory authorities, who will oversee compliance. Electricity market participants, including generators and traders, may benefit from more accurate capacity allocation, potentially reducing congestion costs and improving market efficiency. Consumers could see indirect benefits through more stable wholesale prices, though the immediate effect on retail tariffs is likely negligible. The amendment does not introduce major shifts in regulatory powers but refines existing technical rules within the CACM framework.