The report also recommends strengthening regulatory frameworks and coordination between network operators and large producers to prevent similar events.

The document, prepared by 45 experts from network operators and regulators from 12 countries, again highlights 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 more than 20 years".

Combination of several factors

The research 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 "fluctuations, gaps in voltage and reactive power control, differences in voltage regulation practices, rapid production reductions and generator shutdowns in Spain, as well as unequal stabilisation capacities".

These factors led to rapid voltage increases and cascading shutdowns of renewable energy production, resulting in a blackout across mainland Spain and Portugal, as noted in the preliminary findings presented in October 2025.

Based on these findings, the panel of experts today presented recommendations addressing each of the factors identified in the report, with the aim of preventing similar events in the future.

Rapid restoration

However, they highlight that, despite the unprecedented nature of the collapse, the restoration of the grid was rapid, with Portugal fully regaining grid connection in 12 hours and Spain in 16 hours.

The list of suggestions includes measures such as strengthening operational practices, improving monitoring of system behaviour, and closer coordination and data exchange between electricity system stakeholders.

Strengthening coordination

ENTSO-E emphasises that strengthening coordination between transmission and distribution network operators - in Portugal, REN and E-Redes - and large energy producers and consumers "is essential to effectively manage complex events like this".

"Sustained efforts to improve operational practices and information sharing will contribute to maintaining security of supply for all consumers," it says.

Need for adaptation

The research 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 strengthen the system's resilience with solutions that are already technologically available," the experts explain.

"This blackout highlights how developments at the local level can have implications on a system-wide scale and underscores the importance of maintaining strong links between the behaviour and coordination of systems at the local and European levels, while ensuring that market mechanisms, regulatory frameworks and energy policies remain aligned with the physical limits of the system," they emphasise.

However, they emphasise that monitoring the implementation of the recommendations presented does not fall within the expert panel's mandate.

"Any responsibility for the analysis, monitoring and implementation of the recommendations rests exclusively with each recipient," the document states.