Iberian Blackout Was ‘First Of Its Kind’, EU Expert Panel Concludes

 October 4, 2025 

By EurActiv

By Nikolaus J. Kurmayer

(EurActiv) — The catastrophic grid failure that brought Spain and Portugal to a standstill on 28 April was wholly unprecedented, according to a ‘factual’ report from grid operators – who, after five months probing the causes of the blackout, have shied away from singling out any of the various actors involved in making it one of Europe’s worst-ever.

The incident was the worst power system failure in Europe in over 20 years and the “first of its kind” in the world, said Damian Cortinas, who chairs the European transmission system operators body Entso-E, while presenting the report in Brussels on Friday. 

In the past, blackouts have typically been caused by a sharp drop in voltage, but Spain’s grid appears to have collapsed because of too much of a good thing.

“It was more or less a typical spring day,” said Klaus Kaschnitz of Austrian high-voltage grid operator APG, who was joint leader of the investigation. In Spain, that meant high shares of solar and wind power in the mix, and wholesale power prices hovering close to zero.

The dominoes fall

Then the voltage in the Spanish grid, which usually operates at the standard 400 kV, began to increase.

Spain allows greater leeway than other EU countries, meaning the grid continues to function with voltages pushing 435,000 volts (435kV), Cortinas explained. Elsewhere in Europe, reaching 420 kV usually triggers emergency action.

At the same time, the frequency of the AC current – another key variable in grid management, normally a stable 50 Hertz – began to fluctuate, triggering the shutdown of a power line to France – one of the only links between Iberia and the wider European network, and which otherwise could have helped stabilise the system.

Voltage problems subsequently returned, pushing the network to the point of collapse between 12:32 and 12:33. 

When a transformer in Granada and a solar plant in Badajoz, both in the country’s south, went offline in the space of seconds, the game was up – an otherwise normal day saw Portugal and Spain plunged into chaos.

“After the third incident, we had already reached a voltage above 440 kV, this was more or less the point of no return,” said Kaschnitz. The report is a 260-page technical assessment of a novel type of blackout.

“We have never had a blackout due to over-voltage; this is new to us,” Kaschnitz said.

The last European blackout comparable in scale hit the whole of Italy back in 2003, but that was caused by overloaded cross-border cables and was preceded by a precipitous loss of voltage in the grid. It happened over minutes rather than seconds, as was the case in the Iberian Peninsula.

‘Unprecedented’

“This was an unprecedented event,” said the EU’s Energy Commissioner Dan Jørgensen, who described the events in Spain as a “first of its kind incident [that] highlights that Europe’s energy system faces new challenges”. 

Electricity system specialists have been warning for years that the development of Europe’s power grid has failed to keep pace with the transition from coal- and gas-fired generation to more sustainable sources like wind and solar.

In 2023, Spain spent more to manage its already congested transmission grid than it invested in its development, the UK-based think tank Ember warned last year.

“As power systems evolve, enhanced grid upgrades and a focus on clean flexibility are essential for resilience,” Ember senior analyst Chris Rosslowe said today.

The problem has been recognised both by governments and the European Commission, which produced an ‘action plan’ two years ago. The EU executive plans to present in the coming months a ‘grids package’ of measures to support the overhaul of a network of power lines that in many cases has not been upgraded in decades.

A final report, with recommendations for remedial action, is expected in the first quarter of 2026. But there is no expectation that any one protagonist – whether it be Spain’s transmission grid operator Red Eléctrica, the government itself, or the operators of conventional or renewable generation plants – will be blamed in full.