Disclaimer

The documents and materials published on this web page by ENTSO-E are considered working documents and are provided for general informational purposes only. These documents are based on the most current information available to ENTSO-E at the time of publication. Thus, the information contained herein may be updated, modified, or replaced as new data becomes available or circumstances change.

ENTSO-E makes no representations or warranties, express or implied, as to the completeness, accuracy, reliability, or suitability of the information contained in these documents. Users are encouraged to verify the information independently and consult directly with ENTSO-E for the most recent and authoritative updates.

By using this web page, you acknowledge and accept that the content may be revised at any time without prior notice, and ENTSO-E shall not be held liable for any loss or damage arising from the use or reliance on the information provided.

Introduction

On 28 April 2025, at 12:33 CET, 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

All information published to date, including the present communication, is based on the preliminary findings by the Expert Panel and may change at any time. The investigation follows the legal framework under the European Union Regulation (EU) 2017/1485 of 2 August 2017 establishing a guideline on electricity transmission system operation (SO GL).

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.

Preliminary findings indicate that during the half hour preceding the blackout, two 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 CET. Preliminary analysis of the available information indicates that this was a local oscillation, primarily affecting the Spanish and Portuguese power systems.

The second oscillation started at 12:16 CET to 12:22 CET. This was an inter-area oscillation corresponding to the well-known East-West Continental mode. It was effectively mitigated through countertrading measures, which reduced power flows between France and Spain, also with a switch from AC emulation to fixed power in the operation mode of the HVDC link and 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 the 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 Iberian Peninsula 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

Following the blackout incident, on 12 May 2025, ENTSO-E set up a joint Expert Panel in line with Art. 15(5) of the Regulation (EU) 2017/1485 of 2 August 2017, establishing a guideline on electricity transmission system operation (SO GL) and the Incident 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

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 and Analysis: 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.
2. Recommendations: Based on the findings, the Panel will establish recommendations to help prevent similar incidents in the future. These will be published in a final report 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.

Expert Panel meetings

• 12 May 2025
• 3 June 2025
• 23 June 2025
• 15 July 2025

FAQ

A Frequently Asked Questions (FAQ) section is being drafted separately and will be added to this page once finalised.

Publications & documents

• 28/04/2025Press release: Incident in the power systems of Spain and Portugal
• 1/05/2025Press release: Iberian 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
• 9/05/2025Press release: ENTSO-E expert panel initiates the investigation into the causes of Iberian blackout
• 28/05/2025Letter to MITECO - Data Collection for the investigation of the 28 April 2025 Iberian Blackout by the Expert Panel
• 28/04/2025Letter 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