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Introduction

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.

This page provides consolidated information on the incident, including the affected areas, a preliminary sequence of events, the restoration process, and details about the Expert Panel established to investigate the causes. Further updates will be provided as the investigation progresses.

Affected Area

The blackout impacted the entire Iberian Peninsula, encompassing both Spain and Portugal. Additionally, in France, a small area near the Spanish border experienced disruptions for a limited duration, and several industrial consumers and generators were affected, more notably a nuclear power unit that tripped around the same time as the incident in the Iberian Peninsula. The remainder of the power system of Continental Europe did not experience any significant disturbance.

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

Preliminary Chronology of Events

A preliminary chronology based on the information known so far has been identified regarding the complex sequence of events which have occurred prior to the blackout. The final description of the sequence of events will be established by the Expert Panel in a factual report, followed by the in-depth analysis and recommendations in the final report which will be published.

System conditions on the morning of 28 April (09:00 – 12:00 CEST)

During the night of 27 to 28 April, the Iberian power system operated normally, without notable variations in the voltage profile. From approximately 09:00 CEST, the variability of the voltage in Spain started increasing but without significant variations until 10:30 CEST. From 10:30 CEST, more significant voltage variations started to occur as illustrated in Figures 2a and 2b.

Figure 4 provides a visual representation of the voltage distribution at 12:00 CEST in the 400 kV network of Spain and Portugal (400kV corresponds to 1 p.u.). At that moment, the voltage was again close to 400 kV, after the voltage variations described above :

System conditions prior to the incident (12:00 – 12:30 CEST)

During the half hour preceding the blackout, two main periods of oscillations (power and frequency swings) were observed in the Continental Europe Synchronous Area (CE SA).

The first one took place from 12:03 to 12:07 CEST. Preliminary analysis of the available information indicates that this was a local, forced oscillation (i.e. induced by an external source), with a dominant frequency of 0.64 Hz, primarily affecting the Spanish and Portuguese power systems. As visible in the Figure 5, the forced oscillation excites also the interarea mode East-Centre-West (0.21 Hz) with a small amplitude.

After these first oscillations, the operation mode of the HVDC link between Spain and France was changed to fixed power, set up from 12:11 CEST, as a mitigation measure to stabilise the system. Additional measures (shunt reactors manoeuvres, topological changes to minimize system impedance) were also applied to further improve the system damping.

The second oscillation occurred between 12:19 and 12:22 CEST. This was an inter-area oscillation, with a dominant frequency of 0.21 Hz, corresponding to the well-known East-Centre-West Continental mode.

This second oscillation was effectively mitigated through countertrading measures, which reduced power flows between France and Spain, also with the coupling of the internal power lines in the South of Spain.

Following the second oscillation, the voltage was within the range of 390–420 kV, before increasing again, but still within the operational voltage range in the transmission network. At that moment, Spain’s international scheduled exchanges – all in the export direction – were 1,000 MW to France, 2,000 MW to Portugal and 800 MW to Morocco.

Restoration Process

Following the incident, each impacted Transmission System Operator (TSO) immediately activated their respective system restoration plans, elaborated in accordance with Commission Regulation (EU) 2017/2196 establishing a network code on electricity emergency and restoration (NC ER), as well as any other relevant procedures and protocols for restoring the voltage of the electricity system.

Power system restoration in some regions of the Portuguese and Spanish systems was facilitated, among others, by the activation of the power system resources such as black-start processes in certain power plants, as well as by the existing interconnections with France and Morocco.

The rapid restoration of supply in Spain and Portugal demonstrated the preparedness and efficiency of the affected TSOs, Red Eléctrica and REN with the support and collaboration of the French TSO RTE, as well as the Moroccan utility ONEE. This was possible by the joint work and cooperation of TSOs developed over the years, both between the control centres and within ENTSO-E. In addition, the real-time monitoring and coordination of the status of the European electricity systems was achieved by the European Awareness System platform, a tool developed by all TSOs within ENTSO-E.

Expert Panel Investigation

Following the blackout incident, on 12 May 2025, ENTSO-E set up a joint 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 reporting and classifying 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 Committee
• 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

Investigation Steps

On 12 May 2025, the Expert Panel initiated its investigation into the causes of the blackout. The investigation is conducted in two phases:

1. Data Collection for the Factual report:
   In the first phase of the investigation, the Panel will collect and analyse all available data on the incident to reconstruct the events of 28 April and determine the causes of the blackout.
   For the data collection task, the Expert Panel has been receiving information from all affected TSOs. In addition, to facilitate the provision of third-party data to the Expert Panel, two letters were sent – one to Red Eléctrica and the other one by ENTSO-E to Spanish authorities. Both letters are available on this webpage. As a result, the Panel confirms that it has received data from 32 parties. The Panel is still in the process of assessing the data delivered by these parties. Data has not yet been provided by 9 parties. The Expert Panel is contacting these parties directly to obtain the necessary data.
   At the end of this first phase, the Expert Panel will deliver a first, factual report, to present the facts and data about the incident. Although the legal deadline to produce this report is 28 October 2025, six months after the incident, the Panel intends to deliver it earlier.
2. Recommendations for the Final report:
   In the second phase, the Panel will perform a detailed analysis and will establish recommendations to help prevent similar incidents in the future. These will be published as a final report. The final report is expected to be delivered 2 to 3 months after the factual report. This report will be published and presented to the European Commission and Member States via the Electricity Coordination Group.

Based on the data collected so far, it appears that two of the main questions that the investigation will seek to answer are why the first generation units disconnected from the system, and why the System Defence Plans were unable to halt the process that led to the full blackout of the Iberian Peninsula.

During its investigation, the Expert Panel will also consider the report published by the Spanish government on 17 June, by Red Eléctrica on 18 June, as well as several reports and data directly sent to the Panel by various parties. The Spanish government has officially shared with ENTSO-E the final report of their Committee for the analysis of the circumstances surrounding the electricity crisis of 28 April 2025.

Expert Panel Meetings

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

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, will be organised on 18 July to inform the stakeholders on the progress of the investigation of the Expert Panel. 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 remainder of the power system of Continental Europe did not experience any significant disturbance.

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

   The exact causes of the blackout are still under investigation. 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. ENTSO-E has launched a dedicated webpage to provide updated information on the incident. This page serves as the central source for updates on the investigation of the blackout. The information published is based on preliminary findings and analysis of the Expert Panel, and is subject to change at any time as the investigation progresses.

5. What do we know so far?

   The blackout resulted from a complex sequence of events. Based on the information currently available, the Expert Panel has established a preliminary chronology of the incident, which is available on the dedicated webpage. This chronology will be updated and complemented with additional information as the investigation progresses.

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 the support of the power system resources, including black-start processes in certain power plants, as well as existing interconnections with France and Morocco. A detailed timeline of the restoration process and performed actions is available here: [link to the webpage]

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? Is ENTSO-E working on identifying the causes of the blackout? Is there a specific process?

   In the days following the incident, ENTSO-E and its member Transmission System Operators (TSOs), the Agency for the Cooperation of Energy Regulators (ACER), National Regulatory Authorities (NRAs) and Regional Coordination Centres (RCCs) set up a joint Expert Panel. This Panel is led by experts from TSOs that were not directly affected by the incident, and includes also experts from both affected and non-affected TSOs. The Panel started investigating the root causes of the blackout on 12 May 2025. The investigation is being conducted in two phases. First, the Panel collects and analyses all available data on the incident to reconstruct the events of 28 April and determines the sequence of events which led to the blackout. These insights will be contained in a factual report. In the second phase, the Panel will establish recommendations to help prevent similar incidents in the future, which will be published in a final report. This process follows the (ICS Methodology), established by ENTSO-E 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.

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.

13. There has been talk of a particular atmospheric disturbance in Spain that could have caused the blackout. Is this true?

    AEMET, the Spanish agency for forecasting and climate monitoring, indicated that no ‘exceptional weather events’ were recorded in Spain at the time of the blackout. The theory of an extreme atmospheric event seems to have been spread via a fake document on social media, wrongly attributed to REN (the Portuguese electricity transmission system operator), who denied its validity.

14. How does ENTSO-E address comments in the media about a possible lack of inertia in the system?

    This question is being assessed as part of the investigation by the Expert Panel. The available preliminary data indicates that on 28 April, the Iberian system was operating with sufficient reserves to manage usual imbalances between generation and demand. Miscellaneous questions

Miscellaneous questions

1. 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/

2. 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).

3. How can we ensure that the Expert Panel will provide independent 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. Such Expert Panel is set up after each grid incident Scale 2 (extensive) or Scale 3 (major), as defined in the ICS methodology, and is due to deliver the relevant reports.

   In addition, to ensure transparency, ENTSO-E has launched a dedicated webpage to provide updated information on the incident. This page serves as the central source for updates on the blackout as the investigation continues. The information published is based on preliminary findings and analysis of the Expert Panel, and is subject to change at any time as the investigation progresses.

Publications & Documents

Press releases

• 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

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