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.  

On 9 May 2025, the Swedish and Lithuanian national regulatory authorities (Energy Markets Inspectorate and National Energy Regulatory Council, respectively) requested from ACER a six-month extension to reach a joint decision on electricity cross-zonal risk hedging opportunities at the Swedish-Lithuanian border.

On 11 August 2025, ACER has granted the requested extension. The regulators now have until 12 November 2025 to decide on the matter.

What is this ACER Decision about? 

Cross-zonal risk hedging opportunities are strategies used by electricity market participants to mitigate price volatility risks across different bidding zones. They are important for ensuring the proper functioning of EU's wholesale electricity markets and protecting market participants from price uncertainty.

Under the Forward Capacity Allocation Network Code, national regulatory authorities must assess whether forward electricity markets in their respective bidding zones offer sufficient hedging opportunities. If these are deemed insufficient, the regulators must coordinate to either:

• introduce long-term transmission rights (LTTRs); or
• task transmission system operators (TSOs) with implementing alternative measures that enhance cross-zonal hedging.

To meet this requirement, the Swedish and Lithuanian regulators asked their TSOs to propose alternative measures to improve hedging opportunities in the Lithuanian bidding zone. The TSOs submitted a joint proposal to the regulators, but since some aspects were unclear, the regulators requested more time for a thorough review.

On 2 July 2025, ACER received a proposal from all electricity transmission system operators (TSOs) to amend the methodology for intraday cross-zonal gate opening and closure time. 

What is the methodology about?

Established under the Capacity Allocation and Congestion Management (CACM) Regulation, the methodology sets harmonised rules across EU Member States for when electricity trading can begin (gate opening time) and end (gate closure time) in the intraday market.

The intraday market is a short-term market where electricity is bought and sold on the same day as delivery (e.g. a few hours before), after the day-ahead market has closed. It allows participants to adjust their positions based on updated forecasts and balance supply and demand closer to real time. 

By coordinating these timings across different bidding zones, the methodology supports market integration and the efficient use of cross-zonal capacity within the European electricity market.

Why amend the methodology?

TSOs propose harmonising the gate closure time at 30 minutes before real-time delivery, replacing the current standard of 60 minutes. The gate opening time would remain unchanged. This amendment aims to align the methodology with the requirements of the Electricity Market Design Reform (2024), which seeks to improve the efficiency of short-term markets.

Shortening the gate closure time is expected to:

• allow market participants to trade electricity closer to real time, giving them more time to respond to last-minute changes in demand and supply;
• support the integration of renewable energy sources and flexibility solutions; and
• help TSOs maintain system balance and security of supply.

What are the next steps?

ACER expects to decide on the amended methodology by 2 January 2026.

Interested parties are encouraged to submit comments or questions to ACER-ELE-2025-007@acer.europa.eu by 26 September 2025.

Europe’s clean energy shift is accelerating, and electricity distribution networks must keep pace. From integrating solar panels and electric vehicles to connecting heat pumps and storage, grids need to become more modern, flexible and resilient. To support this, the European Commission’s Action Plan for Grids tasked ACER and the Council of European Energy Regulators (CEER) with providing guidance on electricity distribution planning. 

This guidance provides practical recommendations to help national distribution grid operators align with Europe’s decarbonisation goals and turn grid development into a driver, not a barrier, of the clean energy transition. By promoting more coordinated and inclusive planning, the guidance supports the EU Affordable Energy Action Plan, helping ensure the shift to clean electricity is not only sustainable and secure, but also fair and affordable for all Europeans.

Why grid planning needs a rethink

Distribution networks link homes, businesses and renewables to the wider power grid. Yet most were built for one-way power flows, not today’s decentralised, more flexible generation and fast-growing demand for electricity.

As electrification and renewable growth accelerates, so do the risks of grid bottlenecks and infrastructure development delays. That’s why EU law requires distribution system operators to publish distribution network development plans to outline medium and long-term flexibility needs and investments planned for the next 5-10 years so that the full potential of renewables can be integrated. 

What are the key recommendations? 

• Look ahead: Plan at least 10 years ahead and adopt a proactive approach to avoid grid bottlenecks and enable timely investments.
• Holistic approach: For strategic and efficient results, base electricity grid planning on three pillars: scenario development, network needs assessment and project identification.
• Balance infrastructure and flexibility: Address flexibility needs cost-effectively and ensure national distribution plans provide the necessary input for EU-wide flexibility needs assessment methodology (adopted by ACER today).
• Enhance transparency and public trust: Improve stakeholder engagement through structured publication, open consultations and inclusive communication practices.
• Coordinate: Strengthen cooperation among other system operators and align with broader spatial and sectoral planning to ensure system-wide consistency and efficiency.
• Regulatory oversight: National regulators should scrutinise distribution network development, including monitoring the implementation of plans. 

In a further step towards Europe’s clean energy transition, ACER approves the methodology to be used nationally for identifying non-fossil flexibility needs. This is an important step in developing a common European basis for integrating more renewable energy into the electricity grid and meeting the EU’s decarbonisation targets. This ACER decision directly supports the EU’s Clean Industrial Deal by laying the groundwork for a more resilient electricity system that can power a competitive, low-carbon economy.

The flexibility needs assessment methodology (FNAM), developed by the European Network for Transmission System Operators for Electricity (ENTSO-E) and the EU Distribution System Operators Entity (EU DSO Entity), and approved by ACER, will guide Member States' electricity network operators in identifying how much clean and flexible energy their country needs to handle the variability of demand and supply in their power system. 

What is power system flexibility and why does it matter?

Clean flexibility is the energy system’s ability to adapt quickly to changes in electricity supply and demand, without relying on fossil fuels. It enables:

• Demand response, storage or flexible generation to balance the grid in real time.
• Shifting renewable energy from periods of excess (e.g. windy nights) to times of high demand. 
• Reducing renewables curtailment (wasting renewable energy when the grid can’t absorb it).

Unlocking clean flexibility will cut reliance on gas, enable energy transition in a cost -effective manner and help Member States deliver on the EU’s binding 2030 renewable targets (42.5%) and climate neutrality by 2050. 

What is the purpose of the national flexibility needs methodology?

The methodology distinguishes between two main types of flexibility needs: network flexibility needs and system flexibility needs. Network flexibility reflects the flexibility needed to adjust for grid availability, whereas system flexibility refers to the ability of the electricity system to adjust both power generation and consumption in response to signals from the market.

The flexibility needs assessment methodology provides a harmonised approach for transmission and distribution system operators (TSOs and DSOs) in analysing the national flexibility needs in terms of:

• the data they must collect; and
• how they should assess their national electricity flexibility needs.

This harmonised and unified approach serves both national and EU-wide estimations of flexibility needs, with results feeding into reports that will identify how much flexibility is needed, where and at what cost. 

Each EU Member State shall now:

• Conduct a national flexibility needs assessment (FNA) using the new methodology.
• Submit it to ACER and the European Commission (by July 2026).
• Use the findings to define indicative national targets for non-fossil flexibility (by January 2027).

ACER will then publish an EU-wide report to estimate the flexibility needs including a set of recommendations on issues of cross-border relevance at EU level (July 2027). 

What’s novel about this national electricity flexibility needs methodology? 

This new methodology brings several important advancements to how Europe plans for flexibility, as it:

• Builds on existing studies, such as the European resource adequacy assessment (ERAA) and national resource adequacy assessments (NRAAs), to ensure consistency and prevent overlap. 
• Covers distribution and transmission networks, enabling a full-system view of flexibility needs.
• Relies on distribution network development plans (DNDPs) to bring transparency to local flexibility gaps.
• Quantifies the amount of non-fossil flexibility needed per country to meet EU decarbonisation targets by identifying how much renewable energy can be cost-effectively shifted from periods of surplus to times of high demand – maximising clean energy use and reducing curtailment.
• Accounts for cross-border potential and the role of interconnections in meeting flexibility needs.
• Mandates the EU DSO Entity to issue a guidance, taking into account the ACER-CEER guidance on distribution network planning (issued today), to harmonise flexibility assessments across the EU and align with the EU Action Plan for Grids. 
• Identifies regulatory and market barriers, echoing ACER’s No-regret actions to remove barriers to demand response.

This coordinated approach is essential to delivering a climate-neutral power system, ensuring renewables are fully used.

What’s next?

Member States now have 12 months to prepare their national flexibility assessments. These reports will become vital tools in shaping clean energy investment decisions, grid expansion and modernisation and designing EU policy to accelerate flexibility deployment across borders. 

Learn more about flexibility and ACER's work in this area.

On 2 July 2025, electricity transmission system operators (TSOs) submitted to ACER their proposal to amend how capacity calculation regions (CCRs) are defined across Europe. ACER is now gathering stakeholder views to inform its assessment.

What are capacity calculation regions and why are they important? 

CCRs are cross-border zones where neighbouring TSOs coordinate how much electricity can safely flow between them. This cooperation helps boost cross-border trade, prevent grid congestion and price spikes, and support a more secure, integrated European energy market. 

There are currently nine CCRs in Europe: Nordic, Hansa, Core, Italy North, Central Europe (CE), Greece-Italy (GRIT), South-West Europe (SWE), Baltic and South-East Europe (SEE). They are key to ensuring efficient electricity use, especially as more countries and renewables come into play.

What is the amendment about?

The TSOs are proposing:

• adding three new CCRs to the South-East Europe region to cover borders with Energy Community countries (East-Central Europe (ECE), Italy-Montenegro (IT-ME) and Eastern Europe (EE)); and
• merging two existing regions (Core and Italy North) for several regional processes like intraday coordination and congestion management. 

Your view matters!

ACER is assessing whether the TSOs’ proposal supports market integration, ensures efficient use of the grid and supports the well-functioning of the EU electricity market.

To make an informed decision, ACER is organising a public consultation from 24 July 2025 to 3 September 2025. Submit your views here.

ACER aims to reach a decision by December 2025.