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Report: Renewable energy not to blame for Iberian blackout

Almost a year after the Iberian blackout disrupted millions of citizens across Spain and Portugal, ENTSO-E has published its final report. The findings are clear: the event was not caused solely by renewable energy – but by a complex chain of system dynamics in an evolving energy system.

By State of Green | [email protected]

14 April 2026

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In April 2025, Europe experienced its most severe power outage in over two decades.

At 12:33 CEST on 28 April 2025, large parts of the Iberian Peninsula were abruptly plunged into darkness. Across cities in Spain and Portugal, traffic lights went out, metro systems ground to a halt, and homes, hospitals and businesses were left without power. Within seconds, what had begun as a technical disturbance escalated into a full system collapse, disrupting daily life for millions of citizens and halting critical infrastructure across the region.

In the aftermath, debates quickly emerged around the role of renewables, which plays a significant role in the Spanish and Portuguese electricity systems. Now, a recently published report by the European Network of TSO’s, ENTSO-E, provides a factual and much-needed clarification.

A complex “perfect storm” behind the blackout

According to ENTSO-E, the blackout was caused by a combination of interacting factors – not a single failure.

In the minutes leading up to the incident, the Iberian system experienced oscillations and rising voltage levels. As the situation escalated, a rapid increase in voltage triggered cascading disconnections of generation across Spain.

Within seconds, more than 2.5 GW of capacity was lost. This led to a breakdown of system stability, causing Spain and Portugal to lose synchronisation with the wider European grid and ultimately resulting in a full system collapse.

The report concludes that the blackout was a first-of-its-kind event – a “perfect storm” of system conditions, operational responses and technical limitations.

Discover the report

The final report of the Expert Panel on the 28 April 2025 blackout in continental Spain and Portugal identifies the causes of the blackout and outlines recommendations to strengthen the resilience of Europe’s interconnected electricity system. It was prepared by a technical Expert Panel of 49 members, including representatives from Transmission System Operators (TSOs), Regional Coordination Centres (RCCs), ACER and National Regulatory Authorities (NRAs), and was chaired by experts from two unaffected TSOs.

The rport has been published by the EUropean Network of Transmission System Operators, ENTSO-E, with Danish TSO Energinet assisting and being part of the panel.

Discover the report by ENTSOE

Key findings: system dynamics – not renewable energy

Despite early speculation, the report does not identify renewable energy as the root cause.

Renewable generation levels were within normal ranges, and no single technology was responsible for the incident. Instead, the findings point to challenges related to system operation, coordination and grid management.

The conclusion is clear: System reliability depends on how energy systems are designed and operated – not on the share of renewables.

To prevent similar events, the report highlights several areas for improvement:

Voltage and reactive power management

Maintaining stable voltage levels is fundamental to keeping the power system in balance.

The report highlights how insufficient reactive power control and loss of voltage management were central to the escalation of the blackout.

Strengthening capabilities to manage voltage in real time – across both transmission and distributed assets – will be essential in increasingly dynamic, renewable-based systems.

System monitoring and data transparency

A key challenge identified in the investigation was limited visibility of system behaviour across actors and voltage levels.

Improving real-time monitoring and ensuring access to high-quality data will enable faster, more coordinated responses to disturbances.

Enhanced data exchange between TSOs, DSOs and generators will be critical to understanding and managing system dynamics before they escalate.

Operational practices and coordination

The incident demonstrated how actions taken locally can have unintended system-wide consequences.

While measures were implemented to dampen oscillations, they also contributed to rising voltage levels in the system.

This underlines the need for stronger coordination, aligned operational practices, and a shared understanding of system impacts across borders and actors in an interconnected European grid.

Protection settings and system response

During the incident, several generation units disconnected automatically in response to voltage deviations – some due to protection settings that were not fully aligned with system needs.

Reviewing how assets respond to disturbances, including thresholds and control settings, will help ensure that protective mechanisms support system stability rather than amplify disruptions in critical moments.

Regulatory frameworks

As energy systems become more decentralised and complex, regulatory frameworks must evolve accordingly.

The report points to the need for clearer requirements, incentives and accountability across system actors to ensure that all parts of the system contribute to stability.

Aligning market design, operational rules and technical requirements will be key to enabling a secure and resilient energy transition.

Building resilient and interconnected energy systems

A key lesson from the blackout is how quickly local disturbances can escalate in an interconnected system.

As Europe accelerates electrification and integrates more renewable energy, the need for stronger interconnectivity, flexibility and coordination becomes increasingly important.

Denmark offers a clear example of this in practice. With high shares of wind and solar integrated into the energy system, Denmark maintains a 99.99% security of supply through a combination of grid flexibility, sector coupling and strong cross-border connections.

The Iberian blackout underscores an important point for the green transition:

Renewable energy is not a risk to system stability – but it requires modern, well-integrated and resilient energy systems to unlock its full potential.