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Blackout on the Iberian Peninsula: report sheds light on what happened

At the beginning of October, the European Network of Transmission System Operators for Electricity published its report on the background to the blackout on the Iberian Peninsula, which occurred on 28 April 2025. It confirmed the assumption that overvoltage triggered the blackout, but did not say what caused it.

Almost everyone has experienced a period with no electricity supply in their lives, even if only briefly. According to the Bundesnetzagentur, the power supply was interrupted for 12 minutes on average in 2024 – that is one minute less than in the previous year and below the ten-year average. This means that the German electricity network is one of the most reliable worldwide.

On 28 April 2025, the Iberian Peninsula was hit by a widespread blackout, with massive consequences across the board. In Spain and Portugal, the electricity supply broke down at 12:33 hrs. This considerably affected railway services and local public transport, aviation and the internet. Millions of people in cities like Madrid and Lisbon were without power. It took almost one day to restore the power supply.

^{Final report to provide recommendations for the European electricity network} 

The European Network of Transmission System Operators for Electricity (ENTSO-E) has launched an investigation into the blackout on the Iberian Peninsula and published a report at the beginning of October. An expert panel confirmed that overvoltage was behind the blackout but did not provide any information on the root causes of the outage, saying that further clarification was needed. The final report is to be published in Q1 of 2026 and to be submitted to both the European Commission and the Member States. It will provide an analysis of the causes of the blackout and set out recommendations, which will be relevant for the entire European electricity network.

ENTSO-E has identified a need for further investigation in the areas of voltage control, the behaviour of users of the network, the effectiveness of the system defence plan, the processes governing the restoration of the grid and electricity supply and the exchange of data for improving system operation.

^{System Stability Roadmap for reliable and robust grid operation}

The blackout highlights the importance of reliable grid operation and the necessity to improve the resilience of the electricity grids. To account for these challenges, the Federal Government has developed the System Stability Roadmap in cooperation with the electricity sector. The roadmap is currently being implemented. In addition, transmission system operators were asked to compile a system stability report, which was published for the first time in 2025 and contains recommendations from the Bundesnetzagentur. The Bundesnetzagentur found that many of the recommendations made by the Spanish government (in its reports of 17 and 18 June 2025) have already been implemented in Germany.

The current report by ENTSO-E, an interactive map of the blackout and a detailed FAQ section can be found on the association’s website.