Spain and Portugal Blackout: Causes and Aftermath of the 2025 Power Surge

In April 2025, Spain and Portugal experienced a widespread power blackout affecting approximately 55 million people. A recent report has identified the cause as a series of cascading overvoltages, marking the most severe such incident in Europe in the last 20 years and the first of its kind triggered by overvoltage.

What Caused the Blackout?

The blackout, which began on April 28, 2025, at 12:33 CEST (11:33 WEST), was caused by a surge in electrical voltage within the power network. According to Entso-e president Damian Cortinas, this was the first known blackout caused by overvoltage – a condition occurring when there is too much electrical voltage in a network. Source

The report detailed a sequence of “cascading overvoltages” that ultimately led to the shutdown of the power system. Overvoltage can stem from various factors, including surges due to oversupply, lightning strikes, or insufficient protective equipment. Source Automatic defense mechanisms were activated but proved unable to prevent the complete system failure.

Impact of the Blackout

The power outage lasted approximately ten hours in most areas of the Iberian Peninsula, with some regions experiencing longer disruptions. The blackout significantly impacted daily life, disrupting telecommunications, transportation systems and essential services. Source Metro stations were closed, and traffic lights ceased functioning, causing widespread disruption. Source

Tragically, the blackout was linked to several fatalities. At least seven deaths were reported in Spain and one in Portugal, attributed to circumstances related to the outage, such as fires started by candles or carbon monoxide poisoning from generators. Source More than 25 people sustained non-fatal injuries. Source

The total disconnected load reached 31 GW. Source Minor power cuts were also reported in parts of Andorra and southwestern France. Source

Renewable Energy and the Blackout

The blackout occurred during a period when Spain and Portugal were sourcing approximately 80% of their electricity from renewable sources, primarily solar and wind. Source This led to speculation about the role of renewable energy in the incident, but investigations have not established a direct causal link. Source

Investigations and Findings

The Entso-e report supports findings from the Spanish government and power/grid companies. National energy watchdogs and Spanish lawmakers are also conducting separate investigations. Source

Grid Conditions Prior to the Outage

Prior to the blackout, Spain’s power grid was operating with sufficient capacity. At 12:30 on April 28, the grid was supplied with 32 GW of power to meet a demand of 25 GW, exporting 2.6 GW to Portugal, 0.87 GW to France, and 0.78 GW to Morocco. Source The remaining power was used for hydropumping (3 GW). Source The power supply breakdown was as follows: Solar (19.5 GW, 59.0%), Wind (3.6 GW, 12.0%), Nuclear (3.3 GW, 11.0%), Natural gas (1.6 GW, 5.00%), and Other (13.0%). Source