Introduction

On 28 April 2025, at 12:33 CEST, the power systems of Spain and Portugal experienced a total blackout. A small area in South West France close to the Spanish border experienced disruptions for a very short duration and several industrial consumers and generators were affected.

The rest of the European power system did not experience any significant disturbance as a result of the incident.

This was the most severe blackout incident on the European power system in over 20 years, and the first ever of its kind.

Figure 1 – Geographic area affected by the incident of 28 April 2025.

Expert Panel

Following the blackout, on 12 May 2025, ENTSO-E set up an Expert Panel in line with Article 15(5) of the Commission Regulation (EU) 2017/1485 of 2 August 2017 establishing a guideline on electricity transmission system operation (SO GL) and the Incident Classification Scale (ICS) Methodology. The ICS Methodology is the framework for classifying and reporting incidents in the power system and for organising the investigation of such incidents and is especially relevant to the work of the Expert Panel.

In line with the legal requirements of both SO GL and the ICS Methodology, when the incident is classified according to the ICS Methodology criteria as scale 3 incident – blackout – the Expert Panel is tasked to investigate the root causes of the incident, produce a comprehensive analysis, and make recommendations in a final report which will be published.

The Expert Panel consists of representatives from TSOs, the Agency for the Cooperation of Energy Regulators (ACER), National Regulatory Authorities (NRAs), and Regional Coordination Centres (RCCs).

The Panel is led by experts from TSOs not directly affected by the incident and includes experts from both affected and non-affected TSOs. The Expert Panel is led by Klaus Kaschnitz (APG, Austria) and Richard Balog (MAVIR, Hungary).

ENTSO-E Bodies Convenors participating in the Expert Panel

• Olivier Arrivé – as chair of the System Operation Committees
• Robert Koch – as convenor of the Steering Group Resilient Operation
• Albino Marques – as convenor of the Regional Group Continental Europe

Experts from TSOs and RCCs participating in the Expert Panel

Experts from ACER and NRAs participating in the Expert Panel

Expert Panel Meetings

• 12 May 2025
• 3 June 2025
• 23 June 2025
• 15 July 2025
• 18 August 2025
• 2 September 2025
• 19 September 2025

Next meetings scheduled:

• 14 October 2025
• 30 October 2025
• 18 November 2025
• 10 December 2025

Investigation Steps

On 12 May 2025, the Expert Panel initiated its investigation into the causes of the blackout. In accordance with the ICS methodology, the investigation is conducted in two phases:

1. Data collection and factual report

In the first phase of the investigation, the Expert Panel collected and analysed all available data on the incident to reconstruct the events of 28 April. At the end of this first phase, the Expert Panel delivered its factual report, released on 3 October 2025. It describes the system conditions that prevailed on 28 April 2025, provides a detailed sequence of events during the incident and describes how the system was restored after the incident.

The factual report is structured as follows:

• Management Summary
• System and Market Conditions before the Incident
• System Conditions during the Incident
• Systems Restoration
• Regional Coordination Centres’ analysis before the Incident
• Communication of Synchronous Area Monitors and between TSOs
• Classification of the Incident based on the ICS Methodology
• Next Steps

The report highlights the exceptional and unprecedented nature of this incident - the first time a cascading series of disconnections of generation components along with voltage increases has been part of the sequence of events leading to a blackout in the Continental Europe Synchronous Area.

Download the factual report

2. Recommendations and final report

In the second phase, which starts immediately after finalisation of the factual report, the Panel will perform a detailed analysis of the events of 28 April: it will notably analyse the root causes of the incident, evaluate the actions undertaken to control the voltage and to mitigate the oscillations, assess the performance of generators in regard to protection settings and contribution to voltage control, assess the performance of the system defence plan and analyse the various steps of the restoration phase. The final report will also consider the incident in a broader context, such as by examining the behaviour of the Iberian power system on the days preceding the blackout.

Furthermore, in the final report, the Expert Panel will make recommendations aimed at preventing similar incidents from occurring in the future, not only in the Iberian peninsula but across the whole European power system.

The final report is expected to be delivered in Q1 2026. It will be published and presented to the European Commission and Member States.

The exceptional character of this incident highlights the need to improve the resilience the power system in such situations. ENTSO-E sees at least the following technical areas to be further investigated and analysed:

• Voltage management instruments available
• Assessment of grid users’ behaviour in voltage control and disconnections
• Performance of the system defence plan and possible improvement
• Analysis of the various steps of the restoration phase
• Data exchange with stakeholders to enhance relevance and accuracy of system operation

Information to Stakeholders

A dedicated joint workshop of the System Operations European Stakeholder Committee (SO ESC) and of the Grid Connection European Stakeholder Committee (GC ESC), chaired by ACER, was organised on 18 July to inform the stakeholders on the progress of the investigation of the Expert Panel. A second joint workshop of SO ESC and GC ESC will take place on 13 October to discuss the factual report. Detailed information about the role, composition and work of these two Committees is available on the ENTSO-E website (here).

FAQ

1. What happened on 28 April 2025?

   On 28 April 2025 at 12:33 CEST, the power systems of Spain and Portugal experienced a blackout. A small area in France, close to the border with Spain, was also affected for a limited duration.

2. Were other countries affected?

   No. The rest of the power system of Continental Europe did not experience any significant disturbance.

3. Have the causes of the blackout been identified yet?

   The factual report released on 3 October 2025 provides a detailed description of the sequence of events that occurred in the lead-up to and following the blackout. The investigation to determine the root causes of the incident is still ongoing, and their analysis will be presented in a final report, which will be published. Understanding events of this scale and complexity requires time and a rigorous technical and scientific approach.

4. What is ENTSO-E’s role in identifying the causes of the blackout?

   Following the blackout incident, on 12 May 2025 ENTSO-E set up a joint Expert Panel in line with Article 15(5) of Commission Regulation (EU) 2017/1485 of 2 August 2017 establishing a guideline on electricity transmission system operation (SO GL) and the Incident Classification Scale (ICS) Methodology. ENTSO-E facilitates the work of the Panel, which comprises experts from Transmission System Operators (TSOs) and Regional Coordination Centres (RCCs), as well as representatives from the Agency for the Cooperation of Energy Regulators (ACER) and National Regulatory Authorities (NRAs). In accordance with the legal requirements of both the SO GL and the ICS Methodology, when an incident is classified as a Scale 3 incident (blackout) under the ICS Methodology criteria, the Expert Panel is mandated to investigate its root causes, conduct a comprehensive analysis and make recommendations in a final report, which will be published.

5. What do we know so far?

   The blackout resulted from a complex sequence of events. The factual report published on 3 October 2025 provides a detailed sequence of events before and during the incident and describes how the system was restored after the incident.

6. How did the affected Transmission System Operators (TSOs) respond to the blackout?

   Immediately after the blackout, the affected TSOs initiated a coordinated response to restore power across the affected region of France, as well as in Spain and Portugal. In the Iberian Peninsula, where the system experienced a complete blackout, power was restored swiftly and in full. This successful restoration was made possible thanks to the high level of preparedness and operational effectiveness of the involved TSOs – Red Eléctrica (Spain), REN (Portugal), and RTE (France). The Moroccan utility ONEE also provided support to the restoration process.

7. How did the restoration process unfold?

   The established procedures and protocols for restoring the voltage of the power system were activated immediately following the incident. Power system restoration was made possible thanks to existing interconnections with France and Morocco as well as the support of the power system resources, including black-start processes in certain power plants. For a detailed timeline of the restoration process and performed actions, download the factual report.

8. Did other countries help Spain and Portugal? If so, how?

   The restoration of the supply of electricity in Spain was made possible in part through support from neighbouring systems, specifically via the interconnections of Spain with France and Morocco. Interconnections are high voltage transmission lines that link the electricity systems of different countries, allowing cross-border power exchange across the mentioned borders. These interconnections played an important role in the restoration process in Spain. In Portugal, the system restoration initially relied solely on black start processes carried out by two power plants. At 18:36 CEST, support from Spain began through the connection of the first 220 kV interconnection between Portugal and Spain.

9. What are the next steps?

   The Expert Panel has initiated the second phase of its investigation to determine the root causes of the incident and establish recommendations to help prevent similar incidents in the future, This in-depth analysis and ensuing recommendations will be published in a final report.

10. Why does it take time to provide technical answers following such an incident?

    Conducting a rigorous, fact-based analysis of incidents of this magnitude and technical complexity requires time. In particular, it involves a detailed reconstruction of the precise operation of the Iberian, French and broader European electricity system in the hours leading up to the blackout. This approach is in line with the Incident Classification Scale Methodology (ICS Methodology) developed in accordance with Regulation (EU) 2019/943 on the internal market in electricity and Commission Regulation (EU) 2017/1485 establishing a guideline on electricity transmission system operation (SO GL). The ICS Methodology establishes the framework for reporting and classifying incidents on the power system and for organising the investigation of extensive and major incidents. Past experience has shown that such analyses are essential for drawing meaningful conclusions and implementing improvements across the European power system.

11. How long will the investigation take?

    The investigation and analysis of the incident must be carried out by an Expert Panel set up by ENTSO-E in line with Article 15(5) of Commission Regulation (EU) 2017/1485 establishing a guideline on electricity transmission system operation (SO GL) and the Incident Classification Scale (ICS) Methodology. ENTSO-E facilitates the work of the Panel, which comprises experts from Transmission System Operators (TSOs) and Regional Coordination Centres (RCCs), as well as representatives from the Agency for the Cooperation of Energy Regulators (ACER) and National Regulatory Authorities (NRAs). The Expert Panel will conduct the investigation in two phases. In the first phase, the Panel collects and analyses all relevant data to the incident to reconstruct the events of 28 April and determine the sequence of events which led to the blackout. At the end of the first phase, the results of the investigation will be compiled in a factual report within six months of the date of the incident. Considering the magnitude of this incident, the Expert Panel intends to publish the results as soon as technically possible. Based on these findings, in the second phase, the Panel will establish recommendations to help prevent similar incidents in the future no later than the publication of the annual ICS report for 2025. The Expert Panel will report on the progress of its investigation to the European Commission and Member States through the Electricity Coordination Group. ENTSO-E will subsequently publish the results of the Panel’s investigation once the analysis is complete.

12. Was the blackout linked to a cyberattack?

    A cyberattack has been ruled out as a cause of the blackout by the Spanish Government. In addition, the Spanish TSO Red Eléctrica confirmed that there was no cyberattack on its own infrastructure. An investigation into the matter is also underway at Spain’s National Court.

13. Have there been any previous incidents in Europe?

    Yes, there have been blackout incidents in Europe before. The most recent blackout, other than the Iberian blackout, occurred in June 2024 in South-Eastern Europe. The previous incident on this scale was the blackout in 2003 in Italy. On 18 May 2025, North Macedonia also experienced a power system incident that led to a partial blackout in the country. 

    All extensive and major incidents, as defined by the ICS Methodology are investigated by Expert Panels, involving ENTSO-E, TSOs, RCCs, ACER and NRAs. These investigations are conducted in two steps. In the first step, the TSOs and other experts reconstruct the sequence of events that led to the blackout. In the second step, the experts make recommendations for grid operations which address the root causes, aiming to avoid similar incidents in the future. 

    All investigation reports on previous Scale 2 (extensive) and Scale 3 (major) incidents can be found here: https://www.entsoe.eu/publications/system-operations-reports

14. Have there been any previous blackouts elsewhere in the world?

    Yes. Among other countries, Brazil (1999, 2009, 2023), the United States (2003, 2021), India (2012), Argentina, Paraguay and Uruguay (2019), and Chile (2025) have all experienced blackouts (for different reasons).

15. How can we ensure that the Expert Panel will provide neutral and fact-based recommendations?

    The investigation of the incident takes place in accordance with the applicable legal framework. Following the blackout incident, on 12 May 2025 ENTSO-E set up a joint Expert Panel in line with Article 15(5) of Commission Regulation (EU) 2017/1485 of 2 August 2017 establishing a guideline on electricity transmission system operation (SO GL) and the Incident Classification Scale (ICS) Methodology. 

    ENTSO-E facilitates the work of the Panel, which comprises experts from Transmission System Operators (TSOs) and Regional Coordination Centres (RCCs), as well as representatives from the Agency for the Cooperation of Energy Regulators (ACER) and National Regulatory Authorities (NRAs). 

    The Panel is led by experts from TSOs that were not directly affected by the incident and includes 45 experts from both affected and non-affected TSOs from numerous European countries. While the two TSOs directly affected by the blackout actively contribute to the Expert Panel’s work, as foreseen by the legal framework, each of them is only represented by one expert in the Panel. Furthermore, in line with the Expert Panel’s terms of reference, their contribution involves providing input and suggestions for specific chapters in a transparent and constructive manner, but not acting as the primary authors of the respective chapters where their TSO has been involved in any way in the relevant actions for the event. These measures aim to ensure the neutrality of the reports delivered by the Expert Panel.

Publications & Documents

Reports

Press releases

• 3/10/202528 April Blackout in Spain and Portugal: Expert Panel releases comprehensive factual report
• 3/09/202528 April Blackout in Spain and Portugal: Expert Panel confirms factual report publication on 3 October
• 19/08/202528 April Blackout in Spain and Portugal: Expert Panel finalises data collection and prepares factual report
• 16/07/202528 April Blackout in Spain and Portugal: Expert Panel releases new information
• 24/06/202528 April Iberian Peninsula Blackout: Expert Panel releases new information and announces a stakeholder meeting
• 19/06/2025Expert Panel will review the reports on the 28th April blackout published this week by the Spanish government and the Spanish TSO
• 6/06/2025ENTSO-E Expert Panel continues collection of data and identifies next steps on Iberian Peninsula blackout investigation
• 9/05/2025ENTSO-E Expert Panel initiates the investigation into the causes of Iberian blackout
• 1/05/2025Iberian Black-out: ENTSO-E congratulates Red Electrica and REN for the rapid recovery of the electricity systems of Portugal and Spain, and establishes an Expert Panel to investigate the incident
• 28/04/2025Incident in the power systems of Spain and Portugal

Presentations

• 3/10/2025Media briefing on Factual Report

ICS Methodology document

• 4/12/2019Incident Classification Scale (ICS) Methodology

Letters

• 24/06/2025Letter to ENTSO-E from the Vice-President of the Spanish Government and Minister for Ecological Transition and the Demographic Challenge, Ms. Sara Aagesen
• 28/05/2025Letter to MITECO - Data Collection for the investigation of the 28 April 2025 Iberian Blackout by the Expert Panel
• 26/05/2025Letter to Red Eléctrica – Request for Data supporting the work of the Expert Panel for the 28 April 2025 Iberian Blackout

Contacts

• For any further information, please contact info@entsoe.eu
• For media requests, please contact media@entsoe.eu