Today, ACER initiates the review of its Decision 30/2020 on the electricity redispatching and countertrading cost sharing methodology for the Core capacity calculation region.  

What is a capacity calculation region?

A capacity calculation region is a set of electrically interdependent bidding zone borders, where capacity calculation, regional operational security, redispatching and countertrading costs sharing tasks are coordinated by that region’s transmission system operators (TSOs).

The Core capacity calculation region involves the TSOs and bidding zone borders of Austria, Belgium, Croatia, Czech Republic, France, Germany, Hungary, Luxembourg, the Netherlands, Poland, Romania, Slovakia and Slovenia. It is the biggest European region, involving 13 Member States, 16 TSOs and 19 bidding zone borders.

What is the methodology about? 

The cost sharing methodology allocates the costs from redispatching and countertrading remedial actions within a capacity calculation region. These actions are triggered to solve network congestions occurring within the region. 

Specifically, this methodology tracks how each action affects congested network elements and assigns the related costs to the responsible TSOs, based on the order of flow types (loop, internal, allocated and power-shifting transformer flows). Loop flows are charged first, however according to the Electricity Regulation, its portion below a given threshold is exempted.

Why amend the methodology?

On foot of the ACER Board of Appeal Decision of 31 July 2025, ACER is now revising its Decision 30/2020 and the methodology accordingly.

What are the next steps?

ACER aims to adopt its Decision by the end of January 2026.

On 26 September 2025, ACER received a proposal from the European Network of Transmission System Operators for Electricity (ENTSO-E) to amend the methodology for the regional procurement of balancing capacity.

What is the methodology about?

Transmission system operators (TSOs) must always keep the power system in balance. TSOs usually procure the balancing capacity needed at national level, but to lower procurement costs, they may opt for utilising available voluntary balancing bids from other countries (e.g. made available when local capacity exceeds national needs).  If transmission capacity is expected to be available across bidding zones during balancing, these bids can also be used to reduce balancing capacity needs. 

The methodology for the regional procurement of balancing capacity enables regional coordination centres (RCCs) to evaluate how voluntary balancing bids can be utilised effectively across borders. Following this evaluation, regional coordination centres provide TSOs with recommendations to reduce the volume of procured balancing capacity, hence utilising the flexibility of the EU electricity system. 

Why amend the methodology?

As requested by ACER, European TSOs propose to update the reliability parameters used by regional coordination centres to assess the availability of cross-zonal capacity and voluntary balancing bids. This is important as reliability parameters need to reflect the most relevant data, enabling TSOs to procure balancing capacity efficiently, and at the same time managing their operational risks. This change should foster a more transparent and coordinated process and improve the balancing of EU power system.

What are the next steps? 

ACER will decide by 5 January 2026.

Interested parties may submit comments or questions to ACER-ELE-2025-009@acer.europa.eu by 31 October 2025.

Today, ACER publishes its biennial Opinion on the draft lists of proposed projects of common interest (PCIs) and projects of mutual interest (PMIs) for 2025. 

The PCIs/PMIs lists include energy infrastructure projects prioritised at EU level given their impact to significantly enhance the cross-border links among the energy systems of EU countries (and third-party countries in the case of PMIs). These projects can benefit from accelerated permitting procedures, regulatory treatment and funding, as they are identified as key contributors for integrating renewables, boosting cross-border capacity and advancing Europe’s climate and energy goals.

What is the role of ACER?

ACER’s role in the PCIs/PMIs selection process, as defined by the TEN-E Regulation, is to verify that the relevant methodologies and criteria are applied consistently and transparently across regions in the projects’ selection process. A fair and credible process ensures that the most beneficial projects are prioritised in developing trans-European energy infrastructure. ACER’s role is not to give a ‘second opinion’ on the merits of the different projects nor to help decision makers rank such projects for ultimate selection.

What are the key conclusions?

In its Opinion, ACER found:

• Delays in the availability of Ten-Year Network Development Plans (TYNDPs) data and their cost-benefit results, which hindered the projects’ assessment.
• Infrastructure needs have been identified only per Member State, without sufficient identification of capacity needs per border.
• Unclear distinction of monetised and non-monetised benefits in the ranking of projects, reducing clarity on how these are prioritised.
• Lack of justifications of the projects added on top of the formal proposals from the Regional Groups. The Regional Groups are chaired by the European Commission and include representatives from Member States, transmission system operators, project promoters, energy regulators and ACER. Their role is to assess the projects' potential contribution to EU energy priorities.
• Difficulty for regulators, due to insufficient data, to properly assess several hydrogen project candidates, including their underlying benefits, in the lists. 
• The draft PCIs/PMIs lists do not clearly distinguish between mature and less mature electricity projects.

As these obstacles may affect the credibility and robustness of the selection process, ACER recommends to:

• Deliver the TYNDP data on time and in good quality for the PCIs/PMIs selection process.
• Introduce an assessment of capacity needs per border per each energy vector, thus improving the needs assessment methodology.
• Clearly distinguish between projects’ monetised and non-monetised benefits.
• Ensure greater transparency in complementary project evaluations, if these can’t be avoided.
• Ensure that the complete set of project data is made available for the national regulatory authorities’ assessment in due time, to allow them to conduct thorough and consistent analyses.
• Introduce maturity criteria for electricity projects to clearly distinguish between mature and less mature projects on the electricity PCIs/PMIs lists. This would ensure transparent prioritisation and allow support for less mature projects when they are ready for construction.
• Consider multiple scenarios, in line with ACER’s Scenario Guidelines, to test the robustness of results.

What are the next steps?

By addressing these issues, the PCIs/PMIs selection process will become more transparent, consistent and credible, ensuring Europe invests in the right infrastructure to meet its energy and climate goals.

On 27 March 2025, ACER received the transmission system operators’ (TSOs’) proposal to amend the harmonised allocation rules (HAR) for long-term electricity transmission rights.

The harmonised allocation rules apply to all long-term transmission rights allocations conducted within the European Union, specifying criteria for their auctioning (including use and curtailment of long-term transmission rights, eligibility criteria, etc.). 

The TSOs’ proposal included various updates related to arrangements with market participants, reflecting upcoming market changes (e.g. introduction of 15-minute market time unit in the day-ahead electricity market) and recent incidents (e.g. single day-ahead market decoupling in June 2024). 

To take an informed decision, ACER consulted stakeholders during Spring 2025.

What did ACER decide?

ACER approves the TSOs' proposal, while adding some clarifications and proposing further reviews on the:

• Usage of the day-ahead price for remunerating long-term transmission rights in case of decoupling: ACER recommends TSOs and national regulatory authorities to review the arrangements among nominated electricity market operators (NEMOs), which should set transparent rules for defining the single day-ahead reference price in case of decoupling. 
• Relevant rules for the nomination of physical transmission rights: ACER recommends TSOs and national regulatory authorities to review the applicable nomination rules, considering the introduction of 15-minute market time unit in the day-ahead market.

ACER agreed with TSOs to tackle improvements to the collateral requirements in long-term flow-based auctions separately. 

What are the next steps? 

TSOs and regulatory authorities should now review nomination rules and multiple NEMOs' arrangements to reflect the latest updates introduced by ACER. 

Ahead of the European Commission’s Grids Package proposals (expected in Q4 2025), ACER sets out its recommendations for revising the current legal framework for grids.

Europe’s power grids need to be upgraded, expanded and optimised to connect more planned renewables and thus speed up a cost-efficient clean energy transition.

The European Commission estimated that investment needs for electricity grids will amount to €730 billion for distribution and €477 billion for transmission by 2040.

The European Commission is developing a Grids Package to improve and simplify the current legal framework. This includes the revision and simplification of the 2022 Trans-European Energy Networks Regulation (TEN-E Regulation), a key framework for European energy infrastructure development.

ACER's recommendations address network development aspects (rather than permitting or financing) to improve the efficiency of the EU network planning process and support a cost-effective energy transition. ACER’s focus is on key key areas of network planning and assessment, including:

• Scenario development and the need for improved coordination within and between ENTSO-E and ENTSOG.
• Identification of infrastructure needs.
• Selection and monitoring of Projects of Common Interest (PCIs).
• Cross-border cost allocation (CBCA).

ACER’s proposals aim to streamline procedures and accelerate the development of key energy infrastructure while reinforcing transparency, regulatory oversight and network planning governance across the EU.

What does ACER recommend?

ACER’s recommendations are grouped into two categories: measures aimed at strengthening the TEN-E process to address existing challenges, and those aimed at simplifying the process. 

ACER proposes practical measures to simplify the Ten-Year Network Development Plans (TYNDPs), streamline the selection and monitoring of Projects of Common Interest (PCIs) and recognise the value of alternative solutions, such as non-wire options, to increase electricity grid capacity. ACER recommends to:

• Strengthen regulatory oversight: enhance ACER’s role in overseeing key methodologies for scenario development and infrastructure planning at the European level.
• Improve identification and prioritisation of infrastructure needs: establish effective mechanisms where possible within the current framework to ensure that critical infrastructure gaps are identified and addressed with the most suitable solutions.
• Streamline and simplify TEN-E processes: build on lessons learned from network development, PCI selection and PCI monitoring for more efficient and transparent processes.

While some of ACER’s recommendations require amendments to the current legal framework, others could be achieved through better implementation of the existing regulatory framework.

What’s next?

1. The European Commission proposals to revise the TEN-E Regulation as part of the upcoming European Grids Package are expected in Q4 2025. 
2. ACER stands ready to engage in discussions with the EU co-legislators and stakeholders.

ACER releases today an Opinion assessing whether the European transmission system operators (TSOs) followed the EU legal and regulatory framework when performing their bidding zone review study published on 28 April 2025.

Currently, most bidding zones in the EU are defined by national borders. But, under EU law, bidding zones must be formed in a way that maximises economic efficiency and cross-zonal trading opportunities, while ensuring security of supply. To achieve this, a review of the existing bidding zones was needed to identify structural grid congestions and evaluate the potential benefits of alternative configurations.

In the review process, ACER role was to set the methodology and identify alternative bidding zone configurations for TSOs to consider in their review.

The TSOs’ report, which assesses 14 bidding zones configurations across Central and Northern Europe, is intended to help EU Member States decide whether to amend or keep the current bidding zones.

This ACER’s Opinion, addressed to the Council of the EU, assesses whether the TSOs’ study followed the agreed bidding zone review methodology and evaluates the impact of any deviations. It is not intended as a recommendation for Member States’ decisions.

What are the key findings? 

ACER finds the study broadly aligns with the EU framework but significantly underestimates the benefits of re-shaping Europe’s electricity bidding zones. ACER identifies two main shortcomings: 

• Central European TSOs’ coordination level in solving network congestions has been overestimated. Hence, the TSOs’ study undervalues the efficiency gains of alternative reconfigurations that split the bidding zone of Germany-Luxembourg and that link them up with a bidding zone reconfiguration in the Netherlands. ACER estimates the benefits of those configurations in the order of 450-540 million EUR per year, 70% higher than TSOs’ assessment.
• TSOs’ estimated costs for reconfiguring the bidding zones are based on limited stakeholders’ input and do not sufficiently reflect past experiences.

ACER acknowledges the significant work by TSOs and other stakeholders in the study and the overall positive collaboration. The ACER Opinion also draws some recommendations to ensure a more effective and efficient process going forward.

What are the next steps? 

Following the publication of the TSOs’ report (28 April 2025) Member States have six months to decide whether to amend the current bidding zones. If individual Member States wish to amend their bidding zone configuration, but no unanimous agreement is reached among the relevant parties, the European Commission (after consulting ACER) will have six months to decide.

On 4 August 2025, ACER received two proposals from all nominated electricity market operators (NEMOs) to amend the harmonised maximum and minimum clearing price (HMMCP) methodologies for the European day-ahead and intraday markets, respectively.

What are the methodologies about?

Established under the Capacity Allocation and Congestion Management (CACM) Regulation, the HMMCP methodologies describe the automatic price adjustment mechanisms and how they may be triggered in cases of exceptionally high or low prices in Europe’s electricity day-ahead and intraday markets. They also define the maximum and minimum price limits (the so called ‘maximum and minimum clearing prices’) for the European day-ahead and intraday markets.

Why amend the methodologies?

NEMOs propose to include an additional metric (based on market liquidity) among the conditions for triggering the automatic price adjustment mechanism. The purpose of such inclusion is to avoid the potential triggering of the automatic price adjustment mechanisms in cases of low liquidity in the European day-ahead and intraday markets.

What are the next steps? 

ACER expects to decide on the methodologies by February 2026. 

Contact information

Interested parties are encouraged to submit comments or questions to ACER-ELE-2025-008@acer.europa.eu by 31 October 2025.

Relevant documents

All NEMOs proposal to amend the HMMCP methodology for SDAC.

All NEMOs proposal to amend the HMMCP methodology for SDAC (in track changes).

All NEMOs proposal to amend the HMMCP methodology for SIDC.

All NEMOs proposal to amend the HMMCP methodology for SIDC (in track changes). 

Explanatory note - SDAC.

Explanatory note - SIDC.

Today, ACER publishes its Opinion on the updated manual of procedures for the European Network of Transmission System Operators for Electricity (ENTSO-E) Transparency Platform, submitted on 8 July 2025. 

What is the ENTSO-E Transparency Platform?

The ENTSO-E Transparency Platform is a key tool for collecting and centralising electricity data at the European level. It provides open access to information on electricity generation, transmission and consumption, supporting all market participants, including generators, retailers and traders.

Why an ACER opinion?

In line with the Transparency Regulation, ENTSO-E must maintain and update a manual of procedures for the Transparency Platform, defining the data formats, communication standards, technical and operational requirements for data providers, as well as production type classifications. The manual must be developed through stakeholder consultation and submitted to ACER for an opinion before any updates are published. To date, ACER has issued four Opinions on ENTSO-E’s manual.

What are ACER’s main takeaways? 

ACER finds that the updated manual aligns with the objectives of the Transparency Regulation and related EU legislation. In its Opinion, ACER:

• Notes the addition of new data items and definitions, which improve the scope and accessibility of published data. 
• Welcomes ENTSO-E’s efforts on addressing data quality issues. 

ACER recommends further improvements to the manual, including:

• harmonising definitions of data items across legal frameworks;
• improving clarity of publications related to balancing and cross-zonal capacities; 
• strengthening data quality on the platform; and
• considering feedback from previous ACER Opinions.

What’s next?

ENTSO-E should take ACER’s recommendations into account and proceed with publishing the final updated manual of procedures.

Today, ACER publishes its 2025 Monitoring Report on electricity cross-zonal capacities and congestion management. 

ACER Director, Christian Zinglersen, is in Copenhagen today to present key insights from the ACER report at the Council’s informal meeting of energy ministers under the Danish presidency.

The 2019 Clean Energy Package introduced a legal requirement on EU electricity transmission system operators (TSOs) to make at least 70% of their physical transmission capacity available for cross-zonal trade (by the end of 2025 at the latest) on all lines of cross-zonal relevance. This ensures that enough transmission capacity is allocated for cross-zonal trade with neighbours and mitigates discrimination against cross-zonal trade in favour of internal trade.

This ACER report highlights the importance of implementing the ‘70% rule’ to facilitate more cross-zonal electricity trade. Increasing the level of electricity trade between EU Member States enhances the resilience of the power system, optimises available resources and facilitates the efficient integration of renewable energy.

What are ACER’s findings?

• Untapped value of additional cross-zonal trade: Persistent price differences between bidding zones highlight the need for more cross-zonal trade to unlock further market benefits.
• Meeting the 70% requirement would: 
  • Ensure that domestic electricity flows are not prioritised over cross-border trade.
  • Reduce price volatility and price spikes (such as those seen in summer 2024 across South-East Europe).
  • Bring additional welfare to EU electricity markets. In 2024 alone, meeting 70% in the Core region would have provided at least EUR 580 million in economic welfare through more electricity trading, had Core region TSOs implemented the 70% rule. 
• Progress, but work to be done as the ‘end-2025 deadline’ is at risk: While TSOs are progressing (Core region TSOs made available on average 54% of the capacity on the most congested lines in 2024), implementation delays could prevent some of them from meeting the legal deadline (of 70% on all relevant lines) at the end of 2025.
• Growing grid congestion: Delays in grid reinforcement continue to widen the gap between grid development and system needs, ensuring continued reliance on costly remedial actions to relieve grid congestion. In 2024, EU TSOs spent €4.3 billion on 60 TWh (comparable to Austria’s annual electricity consumption) of remedial actions to manage EU power grid congestion.

What are ACER’s recommendations? 

This ACER report underlines the importance of cross-zonal trade as a key source of power system flexibility, helping to shield consumers from price volatility and support the growth of renewables. ACER recommends:

• Member States and TSOs to prioritise the 70% requirement using the different options available e.g. investing in grid-enhancing technologies (non-wire alternatives) to increase network capacity. 
• TSOs and nominated electricity market operators (NEMOs) to continue improving how available cross-zonal capacity is calculated and allocated. 
• TSOs to promptly implement the EU framework for congestion management to ensure grid congestion is addressed efficiently and in a coordinated manner.

Explore ACER’s interactive dashboard for data on cross-zonal electricity trade, congestion management costs and progress in meeting the 70% capacity rule by region.

For the second consecutive year, ACER has approved the European Resource Adequacy Assessment (ERAA 2024) proposed by the European Network of Transmission System Operators for Electricity (ENTSO-E). This approval confirms the ERAA as a reliable tool in assessing EU’s security of electricity supply. As its relevance grows, so does the need for continuous improvements in future editions.

What is the ERAA?

The ERAA is ENTSO-E’s annual assessment on the risks to the EU’s security of supply. It provides a 10-year outlook to help policymakers take informed and timely decisions on security of electricity supply. The next edition, ERAA 2025, will be released in November 2025.

What does ACER say about ERAA 2024? 

ACER’s second approval confirms ERAA is a trusted tool for monitoring the adequacy of electricity resources (see ACER’s communication on the ERAA 2023). It highlights how shortages in one Member State can impact others and emphasises the importance of regional solidarity, showing the value of cross-border cooperation in managing scarcity.

The approved ERAA 2024 reflects ongoing efforts to ensure better alignment with the established ERAA methodology. ACER finds that this year’s edition largely meets expectations due to several improvements:

• More robust estimation of cross-zonal capacities using a flow-based calculation method, in line with current industry practice.
• A more representative selection of weather scenarios.
• Closer alignment with the National Energy and Climate Plans (NECPs) for renewable assumptions.

ACER’s suggestions for improving future editions

To ensure the ERAA evolves in line with the methodology and remains a reliable tool for policymakers, further enhancements are needed in three priority areas:

• Reduce the consistency gap between ERAA’s investment and adequacy modules.
• Improve national assumptions’ transparency by explaining the main drivers behind the estimates (especially for demand).
• In future ERAA editions, explain what has changed compared to the previous one, allowing stakeholders to follow the developments. 

Without these improvements, the ERAA gradually risks falling behind. A lack of alignment between its two modules could disconnect market revenues from investment, weakening the tool’s usefulness. Increased consistency and transparency, both long advocated by ACER, are key to meeting the expectations of policymakers and the wider public. For future editions, a full assessment of the existing capacity markets is necessary to contribute to the European Commission’s ‘fast track’ initiative for streamlining the capacity mechanism approval process. 

What are the next steps? 

As ENTSO-E prepares its proposal for ERAA 2025 (expected by November 2025), ACER remains actively engaged with ENTSO-E, Member States, the European Commission and the Joint Research Centre to foster improvements. ACER’s ongoing efforts include:

• Providing insights on ENTSO-E’s preliminary input data, calling for increased transparency (especially regarding demand assumptions, demand response and investment parameters). 
• Commissioning a consultancy study to explore key adequacy and infrastructure challenges in scenario development for the ERAA and the ten-year network development plan (TYNDP). ACER will hold a webinar on 11 September 2025 to present the study (expected in late August).
• Working with ENTSO-E and other stakeholders on streamlining the ERAA methodology, triggered by the related European Commission’s report. ENTSO-E shall propose revisions to the European methodology by mid-October 2025. ACER will then decide on the amendments by the end of January 2026.

Would you like to dive into the topic?

Use ACER’s updated dynamic dashboard to:

• Explore the data categories used in all ERAA’s editions, including those proposed for ERAA 2025. 
• Compare how the estimated electricity demand varies across past editions. 
• Check the estimates for power resources, such as batteries and gas-fired plants in 2030 (and beyond) for each EU Member State.