Mega power outage in Spain: a perfect cocktail of factors to explain the major dysfunction of 2025

Millions of residents deprived of power, air conditioning, electronic payment systems, elevators and even the metro. The mega power outage of April 2025, which sowed chaos in Spain and Portugal, did not result from a “single cause” but from a “perfect cocktail” of unfavorable and multiple factors, the group of experts responsible for investigating these malfunctions said on Friday.

Their report confirmed the inability of the Iberian electricity system to control surge phenomena, while emphasizing that this widespread outage was not caused by a “single cause”, but by a “combination of multiple interacting factors”, thus leading to the “worst” event of this type in more than 20 years in Europe.

This report is carried out by a panel of 45 European experts mandated to carry out technical investigations and describe the chronological sequence which led to the widespread and uncontrolled breakdown.

A phenomenon of “cascading overvoltages”

The outage in question occurred on April 28 at 12:33 p.m. Spanish time and affected the entire peninsula. It caused chaos in both Portugal and Spain, where residents were deprived of power but also of the internet and mobile phones. In large cities, many traffic jams had formed as traffic lights had stopped working. Air traffic had been disrupted, particularly at the airports of Madrid, Barcelona and Lisbon.

When presenting the preliminary report in October 2025, the group of experts highlighted the phenomena of overvoltages, “a first” in Europe, even in the world, but indicated that the “root” causes of the mega-blackout still remained unknown.

“This is the most serious power outage that Europe has experienced in the last twenty years and the most important thing is that it is the first of its kind” linked to a phenomenon of “cascading surges”, declared at the time Damian Cortinas, chairman of the board of ENTSO-E, the European network of electricity transmission system operators. “This has never happened before in Europe, we are sure of it,” he said in Brussels. And probably “all over the world,” he added.