A final report by the European grid body says a chain of technical problems — not a single fault — triggered the massive power outage that paralysed Spain and Portugal in April 2025.
On 28 April, shortly after midday, large parts of the Iberian peninsula lost electricity.
The disruption knocked out phone and internet services, halted public transport and closed schools and businesses; some communities remained without power for up to 16 hours and a small area of southern France was also affected.
The disturbance began inside Spain and spread to Portugal because the two countries’ power systems are tightly linked.
Entso‑e, which led the investigation, described the event as the most serious blackout affecting the region in around two decades.
Investigators conclude there was no single trigger.
Instead, a rapid and uncontrolled rise in voltage on a day with several simultaneous issues created instability and caused generators to trip in succession.
The report highlights mismatches between how local generators managed voltage and the settings required by the grid operator.
In some cases operators were using manual controls, which delayed the system’s reaction to changing conditions.
It also found the Spanish transmission network operates with a broader voltage band than many neighbours, leaving less room to absorb sudden surges.
At the same time, available reactive‑power resources were insufficient to stabilise the abrupt voltage increase.
Entso‑e avoided assigning blame but issued measures to reduce the risk of another event, including tighter coordination among transmission operators, distribution companies and other stakeholders in the electricity system.
Politically, the blackout prompted finger‑pointing between the government, the grid operator Red Eléctrica and private energy firms.
Critics also renewed debates about Spain’s energy mix and plans to phase out nuclear power.
The report is intended to help shore up cross‑border protections and improve operational practices so the continent’s grids are better prepared for rare but high‑impact disturbances.
