Judgment of the General Court in Cases T-600/23 and T-612/23

December 18, 2025

Energy: the General Court annuls ACER’s decision concerning the management of electricity markets

Index

The case

With its judgement in the joined cases T-600/23 and T-612/23, published on the 1st of October 2025, the General Court annulled a decision of the Board of Appeal of the European Union Agency for the Cooperation of Energy Regulators (“ACER”) – which confirmed ACER’s decision on capacity calculation methodologies for electricity transmission in the ‘Core[GL1] ’ region and namely in Belgium, the Czech Republic, Germany, France, Croatia, Luxembourg, Hungary, the Netherlands, Austria, Poland, Romania, Slovenia, and Slovakia ( “Core region”).

Pursuant to the now repealed Regulation No 714/200[GA2] 9[1], the European Commission adopted Regulation (EU) 2015/1222[2], establishing guidelines on capacity allocation and congestion management in the electricity sector. This regulation sets out requirements for cross-zonal capacity allocation[3] [GL3] and congestion management[4] [GL4] in the day-ahead[5] [GL5] and intraday markets[GL6] [6], [GA7] including the definition of common methodologies for calculating the day-ahead and intraday cross-zonal capacity within different regions. Article 20, in particular, lays down the rules for the introduction of capacity calculation methodologies using a “flow-based approach”, which is defined as a “capacity calculation method in which energy exchanges between zones are limited by power transfer distribution factors (“PTDFs”) and available margins on critical network elements[7]. The capacity calculation for the Core region applies this flow-based approach.

In accordance with Article 9(1) and Article 20(2) of Regulation 2015/1222, the Transmission System Operators (“TSOs”) of each capacity calculation region are required to develop proposals for capacity calculation methodologies and submit them to the relevant National Regulatory Authorities (“NRAs”) for approval. Pursuant to Article 9(10), (11) and (12), the NRAs concerned must try to reach an agreement and adopt a decision on the TSOs’ proposals. If no agreement can be reached, ACER is required to adopt a decision on the TSOs’ proposals or on a revised version thereof.

In the present case, after the NRAs failed to reach an agreement on the proposals submitted to them by the TSOs of the Core region, the matter was referred to ACER, which adopted modified versions of the regional design of the common capacity calculation methodologies through Decision No 02/2019 (“ACER First Decision”).

ACER First Decision was immediately appealed, on 23 April 2019, by Germany’s regulatory authority, Bundesnetzagentur für Elektrizität, Gas, Telekommunikation, Post und Eisenbahnen (“BNetzA”), before ACER’s Board of Appeal, as well as by the Federal Republic of Germany before the General Court on 2 May 2019.

On 11 July 2019, however, by Decision A-003-2019 (“ACER Appeal Decision”), [GL8] ACER’s Board of Appeal dismissed the appeal brought by BNetzA against the initial decision.  

Despite this, BNetzA did not surrender and, on 21 September 2019, brought an action before the General Court seeking the partial annulment of ACER First Decision, as well as the annulment of ACER Appeal Decision. In 2022, the General Court annulled ACER Appeal Decision, stating that the Board of Appeal had failed to properly assess whether the approved methodologies complied with the requirements under the new Regulation (EU) 2019/943 on the internal electricity market, which had in the meantime been approved and repealed the previous Regulation No 714/2009[GA9] [8]. Following the Court’s ruling, the Board of Appeal confirmed ACER’s initial decision, claiming that the methodologies were indeed in line with the applicable provisions of the new regulation.

In response, both BNetzA and the Federal Republic of Germany brought a new action[GL10]  before the General Court, alleging an infringement of Articles 14 to 16 of Regulation 2019/943 and Article 29(3)(b) of Regulation 2015/1222, and seeking the partial annulment of the Board’s decision, specifically in relation to Articles 5(8)(b), 5(8)(c), and 5(9) of the methodologies. Indeed, these provisions imposed specific requirements on the TSOs of the Core region when proposing internal network elements and the relevant contingencies for capacity calculation, making it impossible – or at least more difficult – to apply capacity calculation to internal network elements. BNetzA and the Federal Republic of Germany essentially argued that nothing in the wording of the provisions of Regulations 2019/943 and 2015/1222 allows the inclusion of an internal network element – significantly influenced by cross-zonal exchanges – in the capacity calculation to be made conditional upon the performance of an economic efficiency analysis and of an impact assessment of increasing the threshold for inclusion.

According to the applicants, the Board’s interpretation was inconsistent with the literal and teleological interpretation of Articles 14 to 16 of Regulation 2019/943 and of Article 29(3)(b) of Regulation 2015/1222, from which it is clear that the capacity calculation must include all internal network elements (and the relevant contingencies) that are influenced by cross-zonal exchanges irrespective of whether or not those elements are structurally congested.

The General Court agreed, finding that ACER had overstepped its authority by introducing requirements not grounded in the applicable legal framework. Specifically, the Court found that the contested interpretation, indeed, infringed Articles 14 to 16 of Regulation 2019/943 and Article 29(3)(b) of Regulation 2015/1222, as they do not permit the introduction, into the methodologies at issue, of the requirements at issue, which impose obligations going beyond the mere communication of the list of internal critical network elements (CNEs) (and the relevant contingencies) meeting the PTDF criterion, as referred to in Article 5(8)(a) of those methodologies[9].

Accordingly, the Court, after joining cases T-600/23 and T-612/23, brought respectively by BNetzA and the Federal Republic of Germany, annulled Decision A-003-2019 of ACER’s Board of Appeal, in so far as it adopted Article 5(8)(b) and (c) and Article 5(9) of the regional design of the day-ahead and intraday common capacity calculation methodologies for the capacity calculation region comprising Belgium, the Czech Republic, Germany, France, Croatia, Luxembourg, Hungary, the Netherlands, Austria, Poland, Romania, Slovenia and Slovakia, as set out in ACER’s Decision No 02/2019.

Relevance of the case

The General Court’s annulment of Decision A-003-2019 of ACER’s Board of Appeal marks a significant clarification of the EU’s institutional framework and the limits of ACER’s powers.

This ruling is important for several reasons[GA11] :

  1. Clarification of Regulatory Limits. The Court firmly established that ACER cannot impose additional obligations – such as economic efficiency analyses or impact assessments – that are not explicitly provided for in EU legislation. Specifically, it held that Articles 14 to 16 of Regulation (EU) 2019/943 and Article 29(3)(b) of Regulation (EU) 2015/1222 do not authorize the introduction of requirements that go beyond the mere submission of the list of internal critical network elements (CNEs) that are significantly influenced by cross-zonal exchanges.
  2. Institutional Legitimacy and Legal Certainty. The ruling reinforces the principle of institutional balance by limiting ACER’s regulatory discretion. It confirms that EU agencies must operate strictly within the legal framework established by the legislature and cannot reinterpret or expand it in ways that affect the rights and responsibilities of Member States or national regulatory authorities.
  3. Protection of National Competence in Market Design. The judgment safeguards the role of Member States and national regulators in shaping electricity market structures – particularly regarding structural congestion and bidding zone configurations – ensuring that EU agencies respect national prerogatives and do not overstep their mandate.
  4. Strengthening the Rule of Law in Energy Regulation. By annulling the contested provisions of ACER’s methodologies, the Court emphasized the importance of strict adherence to the legal framework governing the internal electricity market. It also highlighted the need for a literal, contextual and purposive interpretation of EU regulations, ensuring that regulatory bodies act only within the scope of powers delegated to them.

Ultimately, the judgment reinforces the foundational principle that EU institutions must respect the limits of their delegated authority, thereby upholding legal certainty and the rule of law across the Union as enshrined in Article 2 of the Treaty on European Union[GA12] .

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[1] Regulation (EC) No 714/2009 of the European Parliament and of the Council of 13 July 2009 on conditions for access to the network for cross-border exchanges in electricity and repealing Regulation (EC) No 1228/2003, Article 18(5). The full text of the Regulation is available at the following link. The referenced Regulation has been repealed by Regulation (EU) 2019/943 of the European Parliament and of the Council of 5 June 2019 on the internal market for electricity. The full text of the latter Regulation is available at the following link.

[2] Commission Regulation (EU) 2015/1222 of 24 July 2015 establishing a guideline on capacity allocation and congestion management. The full text of the latter Regulation is available at the following link.

[3] Cross-zonal capacity allocation refers to the process of determining and assigning the available transmission capacity between different bidding zones (countries or market areas) in the electricity market. It ensures that electricity can flow efficiently and securely across borders – for example, from a zone with surplus generation to a zone with higher demand – while preventing network congestion and maintaining system reliability.

[4] Congestion management refers to the set of rules, procedures, and actions used to prevent or relieve network congestion in electricity transmission systems. Congestion occurs when the physical limits of the transmission network prevent all desired electricity exchanges between market participants from being realized simultaneously. The goal of congestion management is to ensure efficient use of the transmission network, maintain system security, and facilitate fair and non-discriminatory access to cross-border capacity.

[5] Day-ahead market time-frame’ means the time-frame of the electricity market until the day-ahead market gate closure time, where, for each market time unit, products are traded the day prior to delivery. See for reference Article 2(34) of Regulation (EU) 2015/1222.

[6] Intraday market time-frame’ means the time-frame of the electricity market after intraday cross-zonal gate opening time and before intraday cross-zonal gate closure time, where for each market time unit, products are traded prior to the delivery of the traded products. See for reference Article 2(37) of Regulation (EU) 2015/1222.

[7] See for reference Article 2(9) of Regulation (EU) 2015/1222.

[8] Judgement T-600/23 and T-612/23, par. 13.

[9] Judgement T-600/23 and T-612/23, par. 85.


 [GL1]Speghiamo in nota chi sono le Core region in nota

 [GA2]Please provide the footnote with the link to the Regulation (as added now in track changes) along with the status of it (repealed( and cite the exact provision providing for the possibility of adopting guidelines.

 [GL3]Spieghiamo anche questo

 [GL4]Anche questo

 [GL5]Mettiamo in nota questi concetti

 [GL6]Anche questo

 [GA7]In the relevant footnotes explaining the terms, please also add the specific provision where they are mentioned.

 [GL8]Qui quello che rileva sono le tempistiche, quindi dobbiamo metterle

 [GA9]Please add reference to the General Court’s ruling and specific paragraph reflecting the content of the sentence.

 [GL10]Davanti a chi?

 [GA11]In the core points of the ruling that are exposed below, it is suggested that reference to the specific paragraphs of the ruling are referenced in footnotes or in brackets in the main text.

 [GA12]Suggestion: here you could add a reference to the EU Treaties providing for the rule of law to highlight also the importance of the ruling.

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