Over-voltage triggered Iberian blackout – report

Facebook
Twitter
LinkedIn
Reddit
Email
Extensive investment in Europe’s grid network is needed to keep pace with renewables deployment.
Voltage control was highlighted as a key factor in the Iberian power outage in April. Image: Andrey Metelev via Unsplash.

An expert panel has identified a series of grid failures that led to April’s unprecedented power outage in Spain and Portugal, ruling out renewables as the leading cause.

The European Network of Transmission System Operators for Electricity (ENTSO-E) released its factual report at the end of last week, documenting the sequence of events that led to the Iberian Peninsula blackout on 28 April 2025.

This article requires Premium SubscriptionBasic (FREE) Subscription

Try Premium for just $1

  • Full premium access for the first month at only $1
  • Converts to an annual rate after 30 days unless cancelled
  • Cancel anytime during the trial period

Premium Benefits

  • Expert industry analysis and interviews
  • Digital access to PV Tech Power journal
  • Exclusive event discounts

Or get the full Premium subscription right away

Or continue reading this article for free

The investigation confirmed the blackout was not caused by over-reliance on renewable energy sources, instead pointing to a cascading chain of events compounded by a lack of voltage control.

The blackout, which struck at 12:33 CEST, plunged mainland Spain and Portugal into darkness for approximately ten hours. The ENTSO-E expert panel’s preliminary findings revealed that the incident marked the first known blackout caused by excessive voltage rather than power shortages.

Grid conditions before the collapse

In the critical half-hour preceding the blackout, the Iberian grid experienced two periods of dangerous oscillations that required immediate intervention. System operators implemented corrective measures to address these fluctuations, but these actions inadvertently increased voltage levels across the network.

The report noted that solar and wind generation levels on 28 April remained consistent with preceding days and seasonal averages, dispelling theories that renewable energy overproduction triggered the crisis.

However, the grid’s vulnerability was exposed by a shortage of thermal power plants connected to provide essential voltage control services at the time of the incident. This lack of voltage regulation capability created the conditions for the eventual cascading failure.

The ENTSO-E investigation documented how a series of interconnected failures rapidly escalated beyond the grid’s defensive capabilities. The excessive voltage conditions, combined with insufficient voltage control resources, created a domino effect that overwhelmed the system’s protective mechanisms. The report emphasised that renewable energy generators, including solar photovoltaic and wind installations, were not responsible for initiating or accelerating the blackout sequence.

Following the incident, Spain moved quickly to address identified vulnerabilities. On 12 June, Spanish authorities updated Operational Procedure 7.4 to enable renewable energy sources to contribute to voltage control services—a capability that could help prevent similar incidents in the future.

The ENTSO-E panel plans to release a comprehensive analysis in early 2026, which will establish definitive root causes and provide recommendations for strengthening European grid resilience against similar cascading failures.

The report confirms a mounting body of evidence that renewables were not to blame for the incident, despite some speculation to the contrary.

In a joint statement, trade bodies SolarPower Europe, the Spanish PV association (UNEF) and the Portuguese Renewables association (APREN) welcomed the report and its emphasis on the lack of voltage control in the system.

“The Iberian blackout must be a moment of learning. [We] reiterate our call for accelerated investment in grid resilience, stability and system flexibility – especially by allowing renewables to provide dynamic voltage control and facilitating the integration of battery storage and grid-forming inverters.

“These technologies are already available and should be procured to further support stable voltage levels, managing variability, and delivering renewable-powered energy security.”

Chris Roslowe, a senior analyst at Ember, said: “The blackout in Iberia was a rare event caused by multiple, complex factors. The ENTSO-E report confirms the Spanish government’s findings that relatively few thermal power plants were connected at the time of the incident to provide voltage control services, and some renewable generation disconnected as the system destabilised. The findings contradict numerous claims that an over-reliance on solar power was to blame. This event reinforces what we already knew. As power systems evolve, enhanced grid upgrades and a focus on clean flexibility are essential for resilience.”

21 October 2025
New York, USA
Returning for its 12th edition, Solar and Storage Finance USA Summit remains the annual event where decision-makers at the forefront of solar and storage projects across the United States and capital converge. Featuring the most active solar and storage transactors, join us for a packed two-days of deal-making, learning and networking.
2 December 2025
Málaga, Spain
Understanding PV module supply to the European market in 2026. PV ModuleTech Europe 2025 is a two-day conference that tackles these challenges directly, with an agenda that addresses all aspects of module supplier selection; product availability, technology offerings, traceability of supply-chain, factory auditing, module testing and reliability, and company bankability.
10 March 2026
Frankfurt, Germany
The conference will gather the key stakeholders from PV manufacturing, equipment/materials, policy-making and strategy, capital equipment investment and all interested downstream channels and third-party entities. The goal is simple: to map out PV manufacturing out to 2030 and beyond.

Read Next

October 6, 2025
German solar inverter manufacturer SMA Solar will cut 350 jobs in 2026 as it adapts to the “weak” residential PV market.
October 2, 2025
Spanish waste management company Trabede and energy firm Greening Group will build a solar module recycling plant in Granada, Andalusia, Spain.
October 2, 2025
The European solar sector will lose around 5% of its jobs in 2025, the first contraction in employment for the sector in nearly a decade.
October 2, 2025
PV products using perovskite technology could assume a dominant position within the next ten years, according to module producer Qcells' CTO.
October 2, 2025
FRV Australia has announced the completion of its largest solar project to date, the 300MW Walla Walla Solar Farm in New South Wales.
October 1, 2025
The insurance industry must adapt to evolving risks to head off a 'protection gap' that could undermine the global green energy transition.

Subscribe to Newsletter

Upcoming Events

Solar Media Events
October 7, 2025
Manila, Philippines
Solar Media Events
October 7, 2025
San Francisco Bay Area, USA
Solar Media Events
October 21, 2025
New York, USA
Solar Media Events
November 25, 2025
Warsaw, Poland