A widespread blackout plunged Spain and Portugal into darkness and has been identified as “one of its kind.”
The official report of the European Network of Transmission System Operators for Electricity (ENTSO-E) released on Friday, October 2, identified that the "cascading overvoltage” resulted in the power outage.
It details how a series of uncontrollable power overwhelmed the Iberian Peninsula’s grid causing the safety system to trigger a widespread shutdown.
The blackout plunged millions into darkness and disrupted modern life for nearly a day.
ENTSO-E President Damian Cortinas marked the incident as “new territory” for energy experts. He stated that this is the “first known blackout” that occurred due to “overvoltage.”
He also explained that the report’s aim is to establish facts and isn’t intended to “apportion blame.”
The April 28th blackout left train and railway passengers stuck, switched off phones and internet, stopped financial transactions and caused emergency services to rescue an estimated hundreds of individuals stuck in elevators.
The report goes further and further than earlier studies showing that although automatic defense plans were instigated, the very structure of the grid could not sustain the abrupt sudden self-compounding voltage spikes.
This indicates a severe weakness in which the system security was not adequate to deal with this new form of failure.
The technical discovery has sparked a blame game of political-corporate proportions.
According to the Spanish government, which also concluded in its own investigation that this was a case of both the national grid operator Red Electrica and the individual electricity companies.
By contrast, Redeia, the parent company of Red Electrica, has accused individual coal, gas, and nuclear power plants of failing to meet voltage, and the utilities have accused the grid operator of poor planning.
The energy policy was also a hot area split into a blackout. The speed at which Spain was turning to renewable energy and abandoning nuclear power was suggested by opponents of the political system as a contributing factor to the instability.
This was, however, expressly rejected by the ENTSO-E report, which discovered that the growing reliance of Spain on renewable energy sources had not been a cause of the outage.
The report states that the major challenge in investigation is incomplete data, with the report noting that the most challenging part was to collect data from eight Spanish generation companies.
This gap in data reflects systemic issues in grid management and coordination.
A final report with more detail, due in the first quarter of 2026, will inquire into the causes of the original overvoltage and detail certain recommendations. European Energy Commissioner Dan Jorgensen said that the incident highlights the necessity to update the energy security strategy in the EU, which is being done.
The April blackout is a vivid reminder: with the changing energy environment in Europe, the stability of the system underpinning it should be reinforced in order to make sure that history is not repeatable.