An independent investigation into the extensive blackout that occurred on the Iberian Peninsula in April 2025 has identified 17 contributing factors rather than a single cause. The report, released by the European Network of Transmission System Operators for Electricity (Entso-E) on March 20, highlights issues such as management failures and outdated infrastructure.
The blackout, which took place on April 28, 2025, resulted from a combination of problems, including improperly configured renewable energy arrays, outdated management parameters, unexpected disconnections of rooftop solar panels, and uniquely soft voltage regulation in Spain. Initial blame directed at renewable energy sources was not upheld by the findings.
The incident led to significant disruptions, halting trams, elevators, and escalators, and bringing commerce to a standstill. Damian Cortinas, head of Entso-E, characterized the blackout as “the largest European outage in 20 years,” describing the mix of factors as an “ideal storm.”
Notably, this blackout was unprecedented in nature; typically, blackouts are caused by voltage drops, but this event was triggered by a surge that exceeded the target level of 400 kilovolts. A critical issue was reactive power, essential for stabilizing high-voltage alternating current lines.
The Spanish high-voltage network operator, Red Eléctrica, struggled to maintain control over reactive power levels, resulting in a cascading failure of power plants, including gas and hydroelectric facilities. Red Eléctrica has denied responsibility, attributing the blackout to network oscillations, disconnections of a significant number of small photovoltaic installations, and at least nine erroneous generation shutdowns.
Additionally, the report pointed to systemic management issues. Gas power plants, which play a crucial role in reactive power control in Spain, were operating at less than 75% of their declared capacity at the time of the blackout, with no economic penalties in place for this shortfall. Furthermore, shunt reactors designed to manage reactive power required manual operation in Spain, unlike in France, where these devices operate partially automatically.
The report includes 21 recommendations, 19 of which are directed at high-voltage network operators across Europe, emphasizing the need for better voltage control by electricity generators. It also noted that rooftop solar panels, which provide a significant portion of Spain’s electricity during midday, disconnected early in the blackout. Addressing this vulnerability may require costly upgrades.
The investigation into the April 2025 blackout on the Iberian Peninsula revealed a complex interplay of factors, including management failures and outdated infrastructure. The findings underscore the need for systemic improvements across Europe's high-voltage network operators.
Source: Euractiv