Today, ACER releases its Opinion on Spain’s National Resource Adequacy Assessment (NRAA). This national assessment complements the European Resource Adequacy Assessment (ERAA) 2024, reflecting recent developments in the country’s electricity system, including the integration of the Balearic Islands and Ceuta.

What is a resource adequacy assessment?

The European Resource Adequacy Assessment (ERAA) evaluates electricity resource adequacy across the EU and provides a consistent framework to assess whether additional national measures are needed to ensure security of supply. ERAA is carried out annually by the European Network of Transmission System Operators for Electricity (ENTSO-E) and reviewed by ACER.

Member States can complement the European analysis through national assessments (NRAAs). While based on the ERAA methodology, NRAAs may capture new developments or national specificities not yet reflected in the latest ERAA.

When a national assessment identifies new adequacy concerns, and the Member State informs ACER, ACER must issue an opinion on the differences between the national and European assessments.

What did ACER find?

Overall, ACER finds the Spanish assessment clear, robust and well executed and notes that most differences with the ERAA 2024 are justified by national specificities and local factors.

Spain’s assessment shows higher electricity adequacy risks for 2030. While results for 2028 are in line with the European assessment, the NRAA estimates that by 2030 the country could experience periods when electricity demand exceeds available supply for more than two hours per year, above the national reliability standard that sets the target level of supply adequacy.

These higher projected risks are linked to two differences identified by ACER between the Spanish NRAA and the ERAA 2024:

• Lower storage capacity: The NRAA assumes that only storage projects already planned or under development will materialise. As a result, Spain would have around half the storage capacity estimated in the ERAA for 2030, limiting the system’s ability to balance variable renewable generation and meet peak demand.
• Stricter gas generation assumptions: Spain’s assessment applies lower generation availability for gas turbine fleet based on historical data, including fixed maintenance schedules. This reduces the generation capacity expected to be available during periods of high demand.

ACER finds the assumptions of lower storage capacity and fixed gas turbine maintenance insufficiently motivated for 2030, as they could better reflect the expected evolution of the electricity system. However, their impact on the overall results of the NRAA is limited, as the modelling approach used (based on a resource expansion calculation) tends to compensate for the missing storage capacity. 

What are the next steps?

ACER encourages the Spanish authorities to take its findings into account as the assessment process progresses.

See other ACER’s opinions on national assessments.

ACER’s 2025 electricity Monitoring Report reviews progress in integrating EU electricity markets. It examines forward, day-ahead, intraday and balancing markets, and identifies where rules and projects are delayed.

This year’s edition also highlights weather-driven price volatility, which occurs when unusually low renewable generation coincides with higher-than-normal demand due to exceptional weather conditions.

What trends did ACER find in 2024? 

• EU market integration brings value and helps mitigate high electricity prices.
• Price volatility shows that more flexibility is needed.
• Long-term markets remain illiquid, limiting investment signals.
• Cross-border integration reduces costs, but project delays persist.
• Balancing integration generated €1.6 billion in welfare gains.
• Forward markets lack depth; Power Purchase Agreements (PPAs) are growing but vary widely in design.
• Day-ahead integration is consolidating and intraday markets are evolving.

What are ACER’s recommendations? 

ACER points to several priorities that are key to resilience:

• Reinforcing flexibility by investing in demand response, storage and backup generation.
• Accelerating delivery of delayed cross-border projects through timely completion of interconnectors and adoption of flow-based capacity allocation in intraday markets.
• Broadening transmission system operators' (TSOs') participation in balancing platforms to reduce costs and volatility and ensure more efficient system balancing.
• Strengthening forward markets with more active long-term trading and well-designed PPAs and Contracts for Difference (CfDs).
• Moving to flow-based allocation in the intraday timeframe to ensure efficient capacity use and reduce congestion-related costs.
• Enhancing monitoring and enforcement to ensure rules are applied consistently and consumers benefit.

Check out ACER’s interactive electricity dashboards, with latest data up to Q3 2025. Next update in January 2026.

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. Update: ACER published its Decision on from 15 December 2025.

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.

Update

Update of 5 February 2026: With its Decisions 02/2026 and 03/2026, ACER approved the proposal.

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.