Lisbon, March 20, 2026 (Lusa) – The final report by European experts confirms that the Iberian blackout was caused by cascading failures and recommends strengthening regulatory frameworks and coordination between grid operators and major producers to prevent similar events.
The document published on Friday, prepared by 45 specialists from grid operators and regulators across 12 countries, highlights once again that the blackout that affected Spain and Portugal on 28 April 2025 was the "most serious and unprecedented incident in the European electricity system in 20 years."
The investigation by the European Network of Transmission System Operators for Electricity (ENTSO-E) concludes that the situation resulted from a combination of several interconnected factors, including "oscillations, gaps in voltage and reactive power control, differences in voltage regulation practices, rapid production reductions, and generator shutdowns in Spain, as well as uneven stabilisation capabilities."
These factors led to rapid voltage increases and cascading disconnections of renewable energy production, resulting in a blackout across mainland Spain and Portugal, as indicated by the preliminary findings presented in October 2025.
Based on these conclusions, the panel of experts has presented recommendations addressing each factor identified in the report, aiming to help prevent similar events in the future.
However, they emphasise that, despite the unprecedented nature of the collapse, grid restoration was swift, with Portugal fully restoring grid connection within 12 hours and Spain within 16 hours.
The list of suggestions includes measures such as strengthening operational practices, improving monitoring of system behaviour, and fostering closer coordination and data exchange among electricity system stakeholders.
ENTSO-E highlights that strengthening coordination between transmission system operators and distribution system operators – in Portugal, REN and E-Redes — and major energy producers and consumers "is essential to effectively manage complex events such as this one."
"Sustained efforts to improve operational practices and information sharing will contribute to maintaining the security of supply for all consumers," it said.
The investigation's findings "also underline the need to adapt regulatory frameworks to keep pace with the evolution of the electricity system."
"The blackout of 28 April 2025 was an unprecedented event, and the recommendations aim to bolster the system's resilience with solutions that are technologically available," the experts explain.
"This blackout demonstrates how local developments can have implications on a system-wide scale and highlights the importance of maintaining strong links between system behaviour and coordination at both local and European levels, while ensuring that market mechanisms, regulatory frameworks, and energy policies remain aligned with the physical limits of the system," they say.
However, they note that monitoring the implementation of the recommendations presented does not fall within the expert panel's mandate.
"Any responsibility for the analysis, follow-up, and implementation of the recommendations lies exclusively with each recipient," the document said.
SCR/RYOL // ADB.
Lusa
