Spain Portugal Blackout Report: ENTSO-E Findings on 2025 Event

On a Monday afternoon in late April, millions of people across Spain and Portugal suddenly found themselves in the dark. At 12:33 CEST on 28 April 2025, the Iberian Peninsula went dark in what officials would later call the most severe blackout Europe had seen in over two decades. What followed was a painstaking restoration effort and a sweeping investigation into what exactly went wrong inside the grid.

Date: 28 April 2025 · Scope: Continental Spain and Portugal total blackout · Spain restoration: 99% of power supply · Portugal restoration: Most areas · Cause: Uncontrolled voltage rise

The table below consolidates key facts from the ENTSO-E Expert Panel investigation into the Iberian Peninsula blackout.

Why has the electricity gone off in Spain?

The official investigation points to an uncontrolled, rapid rise in system voltage that overwhelmed the grid’s defenses. According to the ENTSO-E Expert Panel (European network of transmission operators), the cascade began when distributed generation in northern and southern Spain started disconnecting around 12:32 CEST.

Voltage control loss

• The initial phase saw 208MW lost from wind and solar installations in just under a minute
• Simultaneously, a 317MW net load increase added further stress to the system
• The reasons for these early generation losses remain under investigation, per the Renewable Energy World analysis of the factual report

Concurrent factors on 28 October 2025

Between 12:33:17 and 12:33:18, an additional 930MW of wind and solar capacity disconnected across Segovia, Huelva, Badajoz, Sevilla, and Caceres. The trigger was overvoltage—generators protecting themselves by tripping offline. At 12:33:19, the Iberian systems lost synchronism with continental Europe, according to the Renewable Energy World timeline analysis. Total generation loss reached approximately 2GW within 27 seconds.

The implication: gaps in voltage and reactive power control, combined with uneven stabilization across regions, created conditions where the grid’s built-in defenses could not respond quickly enough to contain the cascade.

Has Spain recovered from the blackout?

Spain restored 99% of its power supply following the incident. The restoration process leveraged interconnections with Morocco and France, along with black-start procedures at power plants, according to the FERC analysis (Federal Energy Regulatory Commission report).

99% restoration

• Transmission fully restored at 04:00 CET on 29 April 2025
• The Morocco-Spain interconnector came back online at 13:04 CET on 28 April
• The France-Spain interconnector was reenergized at 13:35 CET the same day

Authorities’ statements

Spanish grid operators confirmed that 99 percent of the country’s power supply had been restored within hours of the blackout. The rapid use of cross-border interconnections proved essential to bringing generation back online, per the Poder360 coverage of the incident timeline.

What this means: Spain’s dependence on renewable generation meant that when solar and wind facilities disconnected during the voltage surge, the grid lost a significant portion of its baseload simultaneously—a scenario the system’s defense plans had not adequately anticipated.

Has Portugal got their power back?

Portugal experienced a total blackout alongside Spain but followed a different restoration path. The country’s transmission system regained full capacity at 00:22 CET on 29 April 2025, according to the FERC report.

Restoration progress

• Portugal relied primarily on black-start procedures at local generation facilities
• The Portugal-Spain tie-line was reenergized at 18:36 CET on 28 April
• The 400kV connection came back online at 21:35 CET the same evening

Affected areas

A small area in southwest France near the Spanish border experienced short-duration disruptions, though the wider French grid remained unaffected. Portugal’s restoration was slightly behind Spain’s, according to the ENTSO-E official page on the incident.

The trade-off: Portugal’s isolated black-start approach worked but took longer than Spain’s use of interconnections, highlighting how interconnected grids can recover faster when neighboring systems are available to provide support.

Where do Spain and Portugal get their electricity from?

Both Spain and Portugal derive approximately 40% of their electricity from solar and wind generation, making them among Europe’s most renewable-dependent grids, according to grid operator data.

Renewable share

• Solar and wind account for roughly 40% of generation capacity in both countries
• The Iberian Peninsula has among the highest renewable penetration rates in Europe
• This high renewable share means the grid is particularly sensitive to sudden generation changes

Solar and wind reliance

The April 2025 incident exposed a vulnerability that comes with high renewable integration. When the voltage surge triggered mass disconnections of solar and wind facilities, the grid lost approximately 2GW of generation within seconds. The AC interconnections to Morocco and France then tripped, completing the separation of the Iberian system from the European grid, per the Renewable Energy World analysis.

The pattern: high renewable penetration creates both opportunities for clean energy and new challenges for grid stability that existing defense mechanisms were not designed to address.

What does the official Spain Portugal blackout report say?

ENTSO-E released its final expert panel report on 20 March 2026, providing the most comprehensive analysis of the incident to date. The 49-member panel—drawn from transmission system operators, regional coordination centers, ACER, and national regulatory authorities—identified 21 recommendations for preventing similar events, according to the ENTSO-E announcement.

ENTSO-E analysis

• The event was classified as the most severe blackout incident in the European power system in over 20 years
• The panel described it as “first of its kind” due to the speed and scale of the voltage cascade
• Prior to the 28 April blackout, no European incident had produced comparable conditions with such rapid voltage-driven generation disconnections

21 recommendations

The recommendations focus on strengthening operations, improving monitoring systems, enhancing coordination between transmission operators, increasing data exchange, and adapting regulatory frameworks to address the evolving nature of power systems with high renewable penetration, per the ENTSO-E final report release.

Timeline: From blackout to recovery

Four events, one clear sequence: the cascade unfolded in under 90 seconds, but full restoration took nearly 16 hours.

The timeline below documents the collapse and restoration sequence with timestamps from multiple official sources. For a comprehensive understanding of this event, consult the Temu Portugal průvodce 2025.

The pattern: the restoration relied heavily on cross-border interconnections for Spain, while Portugal had to lean on local black-start capacity—a difference that lengthened Portugal’s recovery timeline by several hours.

What’s confirmed and what’s still unclear

The investigation has established clear facts about the cascade mechanics, but some fundamental questions remain open.

Expert perspectives on the blackout

The blackout resulted from a combination of many interacting factors, including oscillations, gaps in voltage and reactive power control, voltage regulation differences, rapid output reductions, and generator disconnections in Spain.

— ENTSO-E Expert Panel (49-member investigation team)

This unprecedented event represents the most severe blackout incident in the European power system in over 20 years.

— Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) analysis

The findings underscore the need for regulatory frameworks to adapt in order to support the evolving nature of the power system.

— ENTSO-E Expert Panel

Summary and implications

The April 2025 blackout was not simply a technical failure—it was a systemic event that exposed how modern, renewable-heavy grids can destabilize when voltage control mechanisms fail to keep pace with generator behavior. The ENTSO-E final report issued 21 recommendations, but implementing them will require coordinated action across European transmission operators, regulators, and policymakers. For grid operators across Europe, the lesson is stark: as renewable penetration increases, the systems designed to prevent cascading failures must evolve in step, or similar events will recur.

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ENTSO-E’s findings on the voltage surge and 99% Spanish restoration align with the causes and impacts overview from contemporaneous analyses.

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