Under the EU’s Regulation on forward capacity allocation (FCA), the Baltic national regulatory authorities were required to decide on the capacity calculation methodology for long-term timeframes by 22 March 2025. This followed a proposal from electricity transmission system operators, submitted on 22 January 2025.

On 20 March 2025, the Baltic regulators (Estonia, Finland, Latvia, Lithuania, Poland and Sweden) requested from ACER a three-month extension to decide on the matter.

In their request, the regulators explained more time is needed to: 

• assess the methodology’s compatibility with existing day-ahead and intraday capacity calculation methods;
• evaluate the technical constraints of the proposed allocation; and
• consider potential updates from Poland's electricity balancing market reform.

What is long-term capacity calculation?

Capacity calculation determines how much electricity can be safely and efficiently exchanged across borders in a given capacity calculation region. It ensures that available transmission capacity is calculated in a consistent and transparent way, supporting reliable cross-border electricity trading in both short- and long-term markets.

Long-term capacity calculation focuses on ensuring that there is enough capacity in the power grid to meet future demand over extended periods (months or even years). This supports the EU’s internal energy market by enabling forward electricity trading and allowing market participants to plan ahead and manage price risks.

What are the next steps? 

ACER plans to act promptly on this request, aiming to reach a decision in May 2025.

On 28 April 2025, a large-scale blackout occurred in Spain and Portugal shortly after 12.30 CEST. There was widespread interruption in power supply in the Iberian Peninsula. Some areas in France close to the border were also affected, albeit for a very short period.

Electricity supply in the affected area has been restored, with the help of power generation resources (such as hydro-power plants) and power interconnections with France and Morocco.

Expert Panel to investigate

An expert panel is being set up by ENTSO-E to investigate the incident. This panel includes transmission system operators, regional coordination centres, ENTSO-E. The relevant national regulatory authorities and ACER are also invited to participate. 

The panel will collect the data and first prepare a factual report, followed by the final report that will analyse the causes of the incident and include recommendations to make the system more resilient.  

ACER stands ready to participate in ENTSO-E’s expert panel and to assist in identifying the root causes of this incident, including possible implications to draw going forward.

Background

Large-scale blackouts are rare in Europe, although they have occurred before:

• 8 January 2021: A disturbance split the European grid into two parts, causing frequency deviations and temporary outages across several countries. The re-synchronization of the two regions incident was resolved within an hour.
• 4 November 2006: Imperfect cross-border coordination on a planned transmission line outage led to a cascading grid failure resulting in a system split and outages across continental Europe.

• 28 September 2003: A power line touching a tree led to other lines overheating, leading to a series of grid failures and a blackout affecting more than 50 million consumers in Italy and Switzerland.

The lessons learned from these incidents led to improvements in cross-border coordination, system operation, and market integration.

In April 2025, the European Network of Transmission System Operators for Electricity (ENTSO-E) submitted its proposal for the European Resource Adequacy Assessment (ERAA) 2024 to ACER.

What is ERAA?

Mandated by the 2019 Clean Energy Package, ERAA is ENTSO-E’s annual evaluation of the risks to the EU’s security of electricity supply for up to 10 years ahead. In line with the methodology approved by ACER in 2020, ENTSO-E must carry out an annual assessment to determine whether the EU has sufficient electricity resources to meet future demand.

At the national level, Member States set their own electricity reliability standards, which indicate the level of security of supply they require. At the European level, ERAA assesses whether the results align with the standards set by the Member States.

How does ERAA benefit the EU?

ERAA provides an objective basis for identifying potential risks to the security of electricity supply in Europe, and whether additional national measures, such as capacity mechanisms, are needed.

What is ACER’s role?

Each year, ACER reviews ENTSO-E’s proposal for ERAA, taking into account the relevant scenarios, assumptions, and results. If approved by ACER, the assessment informs national decisions on the security of electricity supply.

Following ENTSO-E's submission, ACER is conducting its review of the draft ERAA 2024 and will issue its decision in July 2025.

Amendment of future ERAA methodology 

In March 2025, ACER was mandated by the European Commission to amend and streamline the methodology for ERAA. This stems from the Electricity Market Design Reform (July 2024) and the European Commission’s report (March 2025), both calling for streamlined and simplified application of capacity mechanisms.

To initiate the process, ACER requested ENTSO-E to propose amendments to the ERAA methodology by mid-October 2025. ACER will then approve or amend the proposal within 3 months of receipt. 

Read more on ERAA.

ACER issues today its guidelines to better protect cybersecurity information exchanged under the EU-wide network code on sector-specific rules for cybersecurity aspects of cross-border electricity flows (NCCS).

These guidelines are issued for the electricity sector, including transmission and distribution system operators, generators, organised markets, nominated electricity market operators (NEMOs) and the balancing responsible parties, as well as for providers of critical information and communication technology (ICT) services and managed security services.

ACER consulted the EU cybersecurity agency (ENISA), the European Network of Transmission System Operators for Electricity (ENTSO-E), EU DSO Entity and the competent authorities under the electricity cybersecurity network code in preparing these guidelines.

Why are these guidelines important?

Entities from the electricity sector (e.g. network companies and others) are required under the binding electricity-specific cybersecurity network code to share information, including on cyberattacks, threats, risk assessments and cybersecurity expenditures. Preserving the confidentiality of such sensitive information when sharing it among themselves and with relevant authorities is important. 

What are ACER's recommendations?

The guidelines suggest:

• Usage of the Traffic Light Protocol (TLP) to exchange information. The guidelines also provide basic instructions for the electricity sector on how to apply it. In case there are no legally binding national classification schemes applicable to the shared information, the TLP can also be used to share information within a Member State.
• Several methods for anonymising and aggregating information. The guidelines also provide examples of how specific information exchanged under the NCCS could be anonymised or aggregated.

Find out more on the NCCS.

ACER has published its opinion on the amended balancing monitoring plan of the European Network of Transmission System Operators for Electricity (ENTSO-E), suggesting more flexible reporting timelines, while stressing the need for improved data quality. 

How balancing works and why it needs oversight

In balancing markets, balancing energy is used to always keep the power system stable by correcting differences between electricity production and consumption. If there is not enough electricity in the system, transmission system operators (TSOs) procure upward balancing energy. If there is too much electricity, TSOs procure downward balancing energy. In most EU countries, this is done via EU platforms for the activation of balancing energy.  

Under the Electricity Balancing Regulation, ENTSO-E is tasked with overseeing the implementation and integration of balancing mechanisms across the EU. This includes coordinating the use of key platforms for the exchange of balancing energy and providing detailed reports to ACER on progress, efficiency and market integration.

However, delays in some TSOs joining key balancing platforms could hinder the timely publication of monitoring reports, as insufficient operational data may be available for analysis. As a result, ACER has suggested more flexible reporting timelines, while stressing the importance of high-quality balancing data. 

What are ACER’s key messages? 

ACER recommends that ENTSO-E:

• Adopts alternative reporting timelines suggested by ACER.
• Prioritises the quality of balancing data published on the ENTSO-E Transparency Platform to ensure that national regulators and ACER can effectively conduct their respective monitoring and analyses. 
• Streamlines reporting and promptly notifies ACER of any overlaps between reporting obligations, without the need to resubmit the amended Monitoring Plan. 

What are the next steps?

ENTSO-E is encouraged to begin improving data quality without delay.

Looking ahead, ACER commits to working closely with ENTSO-E to progressively reduce the number of reports required, aiming for more efficient and focused monitoring processes. 

On 16 April 2025, the European Network of Transmission System Operators for Electricity (ENTSO-E) and the European Distribution System Operators Entity (EU DSO Entity) submitted to ACER a joint proposal on the national flexibility needs assessment methodology. The proposal defines: 

• the methodology for analysing national flexibility needs in electricity systems; and 
• the type of data to be gathered by system operators and in what format.

Why national flexibility assessments matter

The national flexibility needs assessments aim to support Member States in identifying their indicative national targets for non-fossil flexibility (e.g. storage, demand response), ensuring their electricity systems remain secure and efficient during the energy transition. 

How does it link to the EU-wide flexibility assessment and what are the next steps? 

ACER has three months, until 16 July 2025, to approve or amend the system operators’ proposal. Once approved, the methodology becomes binding for national assessments. Based on the national assessments (to be delivered by the national designated entities by July 2026), the Member States must set their national non-fossil flexibility targets within 6 months (by January 2027).

ACER will then review the national reports (by July 2027) and may provide recommendations on issues of cross-border relevance (including on removing barriers) to ensure sufficient non-fossil based flexible capacity is in place. 

In parallel, to complement the national assessments, ACER is working on an EU-wide flexibility needs assessment, which will be published by July 2027. 

The ACER report Unlocking flexibility: No-regret actions to remove barriers to demand response identifies persistent barriers to demand response and proposes 12 no-regret actions to remove them. 

The report is a roadmap and a call to action for policymakers, system operators, regulators, and market participants to act now. These actions will enhance flexibility, improve system efficiency, reduce consumer costs, and support the energy transition.

What are flexibility and demand-response?

Demand is the consumer side of the electricity market. Demand response is when consumers (or aggregators on their behalf) adjust their electricity consumption and generation in response to a change in the electricity market price (or a financial incentive) to increase/decrease/shift the timing of their electricity consumption. 

Power system flexibility is the electricity system’s ability to adjust to changing generation, consumption and grid conditions. Distributed energy resources, including demand response, energy storage, and distributed generation, play a key role in providing this flexibility.

Demand response supports more variable renewable generation and demand-side resources being added to the power grid. When consumers respond to price signals and actively participate in electricity markets, the benefits extend beyond them, helping to reduce price volatility for all consumers.

How is unlocking demand response linked to energy bills and the clean energy transition? 

Consumers have an important role to play in energy markets and the shift to cleaner energy. Enabling demand response supports this transition.

Recognising this, the first action of the European Commission’s Action Plan for Affordable Energy (February 2025) is to make electricity prices more affordable. 

One way to achieve this is by increasing flexibility in the power system. Greater demand response helps reduce price volatility and price spikes, makes it easier to integrate renewables, and increases overall system resilience.

What are ACER’s recommendations?

The ACER report sets out 12 concrete actions to remove the barriers to demand response, calling, for example, for:

• Stronger price signals through dynamic pricing and time-of-use tariffs to encourage consumer participation.
• Simplified market entry allowing aggregators and small players to provide flexibility services.
• Wider adoption of smart meters to enable real-time demand response.

ACER and the national regulatory authorities (NRAs) agree to follow the actions set out in the report and call on policymakers, Member States, system operators, and market players to similarly focus on these 12 actions.

Read more.

Interested in the topic? Read ACER’s recommendation on the Network Code on Demand Response, which provides further insights into the regulatory framework supporting flexibility in electricity markets. 

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.

To inform its decision-making process, ACER will open a public consultation on 24 April 2025.

Why change the rules?

The harmonised allocation rules apply to all long-term transmission rights allocations conducted within the European Union. They provide specifications for the auctioning of long-term transmission rights (including use and curtailment of long-term transmission rights, eligibility criteria, etc.) and go through a review process every two years. 

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

What are the next steps? 

The public consultation will run until 22 May 2025. 

ACER will decide on this amendment by 29 September 2025. 

With its Decision 03-2025, ACER has approved a proposal from Nominated Electricity Market Operators (NEMOs) to amend the single intraday coupling (SIDC) products methodology. 

Why is single intraday market coupling important? 

Before ‘market coupling’ was introduced in the EU, cross-border power grid capacity and electricity had to be bought separately. Now, market coupling (day-ahead and intraday) allocates scarce cross-border grid capacity efficiently by coupling wholesale electricity markets in different regions, while taking into account cross-border power grid constraints. 

With the growth in intermittent renewables (e.g. wind and solar), there is a growing interest in intraday trading for market participants to be in balance after the closure of the day-ahead market and as close to real time as possible. This flexibility benefits both market participants and power systems. 

What is the methodology about?

The SIDC products methodology is defined by the Capacity Allocation and Congestion Management (CACM) Regulation. The methodology specifies the types of products that can be traded within the EU’s continuous single intraday market and in intraday auctions. Here, trading begins the day before delivery and continues through the day of delivery, supporting real-time adjustments to supply and demand across borders.

Why did ACER amend the methodology and what’s new?

The update aligns the SIDC products methodology with the single day-ahead coupling (SDAC) products methodology (amended in September 2024 to allow 15-minute trading). With this change, market participants will be able to trade electricity in 15-minute intervals in both day-ahead and intraday markets, resulting in enhanced market flexibility.

Harmonising trading rules across both markets is necessary to comply with the EU Electricity Regulation and reduce entry barriers for market participants trading short-term products. 

What are the next steps? 

NEMOs are required to implement the amendments promptly after adoption.

Today, ACER publishes its report on electricity network tariff methodologies. This report analyses how network tariffs are set across the EU and how network costs are allocated across different network users (e.g. generators, consumers, battery facilities or other storage operators). 

The report enhances transparency and comparability in electricity network tariff setting by sharing national practices. It also examines and offers insights into various tariff challenges faced by energy regulators. 

How is it relevant to the European Commission’s Action Plan for Affordable Energy?

Network charges finance the operation and upgrade of the power grid. ACER has repeatedly flagged that, for EU competitiveness, network costs need to be contained as they are one of the main drivers of electricity costs.

Action 1 of the European Commission’s Action Plan for Affordable Energy (February 2025) is to make electricity prices more affordable. The ACER tariff practices report, which emphasises fair and cost-reflective electricity network tariffs, is timely as the European Commission puts forward (Q2 2025) a design of tariff methodologies for network charges to incentivise the use of flexibility and investments in electrification.

What are ACER’s key messages? 

• Getting the price signals right is key. As the energy transition advances, network costs are expected to rise (possibly to double by 2050) and account for a bigger share of the electricity bill (see ACER report on electricity infrastructure, December 2024). This calls for a regular ‘fitness check’ by regulators of network tariff methodologies. Ensuring the network tariffs send the right price signals optimises grid use and keeps network costs down.
• Containing the rise in network costs is important for EU competitiveness and affordable electricity. Future-proof measures should ensure all network users receive signals for flexibility and system efficiency, rather than unduly shifting costs among them.
• Network tariffs should be cost-reflective to encourage users to adapt their behaviour. Together with market prices, they provide a combined price signal, influencing users’ electricity generation and consumption patterns. 
• Two-thirds of EU countries have recently made (or plan to make) major revisions to their network tariff methodologies. Many of these changes align with ACER’s past recommendations (including increasing the use of power-based tariffs in alignment with the cost-causality principle, introducing time-of-use signals and removing unjustified discounts).
• Local power system context matters. No ‘one-size-fits-all’ solution can be easily found: this ACER report presents select national practices from which regulators can draw inspiration to increase system efficiencies and keep electricity network costs down, tailoring them to local needs.

ACER offers 10 principles for national regulatory authorities (NRAs) to consider when setting or approving their next electricity transmission or distribution tariff methodologies. These aim to:

• enhance transparency and comparability of network tariff methodologies;
• ensure non-discrimination among network users;
• promote cost-reflectivity and efficient price signals; and
• foster stakeholder engagement before major methodology revisions.

What are the next steps?

ACER will continue to facilitate the exchange of best practices among NRAs, engaging closely with stakeholders to gain valuable insights.  

ACER stands ready to support the European Commission as it develops its guidance on the design of electricity network methodologies (2025) and its Electrification and Grids Package (2026).