ENTSO‑E Report Sparks Blame War Over 2025 Iberian Peninsula Blackout

When ENTSO‑E published its first factual report on the April 28, 2025 Iberian Peninsula blackout, the power sector felt a sudden jolt. The outage struck Spain, Portugal and a slice of southwestern France at 12:33 CEST, plunging millions into darkness and grinding industry to a halt. Early data points to a massive voltage surge the grid could not absorb, but the search for a root cause has already ignited a clash between regulators, transmission operators and the broader European energy community.

Background to the Iberian Blackout

Europe’s power network relies on a delicate balance of generation, transmission and real‑time control. The Iberian system, historically semi‑isolated, is linked to the continental grid through high‑capacity interconnectors with France and, more recently, Morocco. On the morning of 28 April, a confluence of factors—high renewable output, low thermal generation, and a spike in load—created a perfect storm.

The Iberian Peninsula blackoutIberian Peninsula unfolded in two rapid voltage fluctuations. The second wave forced the Spanish system to disconnect from the continental network, triggering a cascade that collapsed the entire Iberian grid.

Timeline of the Outage

• 12:33 CEST – Voltage surge overwhelms the Iberian network.
• 12:35 CEST – Black‑start procedures are launched by Red Eléctrica de España (REE).
• 13:04 CEST – The Morocco‑Spain interconnector is re‑energized, providing immediate support.
• 18:36 CEST – First 220 kV interconnection between Spain and Portugal comes online, restoring bilateral flow.
• 19:00 CEST – Full supply restored across Spain, Portugal and affected French zones.

Coordinated action by the transmission system operators—Red Eléctrica (Spain), REN (Portugal), RTE (France)—and assistance from Morocco’s utility ONEE kept the blackout to a matter of hours.

Official Findings and the Growing Dispute

On 9 May, ENTSO‑E released a preliminary timeline, but left causation open. The agency set up an expert panel to deliver two separate reports: one on technical causes, another on policy recommendations, the latter slated for Q1 2026.

Meanwhile, the Spanish government’s own investigation, issued on 17 June, placed blame on a cluster of small outages in southern Spain that ignited a chain reaction. The report singled out REE for not having enough thermal power plants online and for mis‑timing its dispatch calculations.

REE fought back the next day. Concha Sanchez, Chief of Operations at Red Eléctrica de España told reporters, “Based on our calculations, we had sufficient voltage‑control capability. If conventional generators had performed their voltage‑control duties, the blackout would not have happened.” She added that adding a single natural‑gas plant would not have changed the outcome.

Industry representatives slammed Sanchez’s comments, accusing REE of shifting responsibility and neglecting its duty to “safely cover all the system’s needs.” The debate has highlighted a deeper split: whether the failure was primarily a technical shortfall in voltage regulation or a strategic planning error in generation mix.

Restoration Efforts and Cross‑Border Cooperation

The speed of recovery was impressive. Within two minutes of the loss, black‑start protocols were activated, and by early afternoon the Morocco‑Spain link was feeding power back into the system. The 220 kV line between Spain and Portugal, re‑energized at 18:36 CEST, was the final piece that allowed full restoration.

What made this possible was the robust “spare‑capacity” arrangement that European TSOs have maintained for decades. France’s grid, operated by RTE, supplied emergency power, while Morocco’s ONEE contributed via the Iberian‑African interconnector, a reminder that the European power market is increasingly interdependent.

Implications for Grid Resilience

Across the reports, a common thread emerges: a lack of voltage‑control resources. At the time of the incident, renewable generators were barred by law from providing reactive power support, a key tool for stabilizing voltage. Spain responded on 12 June by amending Operational Procedure 7.4 to let renewables contribute, though full compliance will stretch into 2026.

The U.S. regulator FERC weighed in, citing poor voltage‑ride‑through performance, limited dynamic voltage regulation, and gaps in operations planning as primary contributors. Their analysis warned that over‑voltage‑induced tripping could cascade into under‑frequency load shedding, compounding the crisis.

For policymakers, the blackout underscores the urgency of modernising voltage‑control frameworks, integrating renewable reactive‑power capabilities, and maintaining adequate thermal backup until those capabilities are fully proven.

Looking Ahead: What to Expect

ENTSO‑E’s deep‑dive report, expected in early 2026, should shed light on the exact chain of events and propose concrete steps. In the meantime, Spain, Portugal and France are tightening inter‑operator coordination, and the European Commission is likely to review the legal barriers that kept renewables out of voltage‑control markets.

Energy analysts predict that the Iberian experience will become a case study for other semi‑isolated regions—like the Baltic states and parts of the UK—seeking to balance high renewable penetration with grid stability.

• April 28 2025 – Voltage surge triggers Iberian blackout.
• June 12 2025 – Spain updates Procedure 7.4 to let renewables aid voltage control.
• June 17 2025 – Spanish government blames REE for insufficient thermal capacity.
• June 18 2025 – REE’s Concha Sanchez pushes back, cites conventional generator failure.
• Q1 2026 – ENTSO‑E to release full technical analysis and policy recommendations.

Frequently Asked Questions

What triggered the voltage surge on April 28, 2025?

The surge was the result of a sudden mismatch between high renewable output and insufficient reactive‑power support from conventional generators. With renewables barred from voltage control, the grid could not absorb the rapid change, causing the cascade.

How did the blackout affect ordinary consumers?

Around 12 million households across Spain, Portugal and a border region of France lost power for roughly six hours. Essential services such as hospitals switched to backup generators, while traffic lights and public transport were temporarily halted.

Why does the Spanish government blame REE?

The government report says REE’s dispatch calculators underestimated the need for thermal plants during midday peak hours, leaving the system under‑prepared when the voltage spike hit. They argue that more gas‑fired units should have been online.

What changes is Spain implementing to avoid a repeat?

Spain’s updated Operational Procedure 7.4, effective June 12, 2025, now permits renewables to provide reactive power for voltage control. The rule will be fully rolled out by early 2026, and additional thermal reserve margins are being examined.

When will ENTSO‑E’s full analysis be published?

The agency has slated the comprehensive technical report for the first quarter of 2026. It will include a root‑cause investigation and a set of recommendations aimed at bolstering European grid resilience.