On April 28, 2025, both Portugal and Spain experienced a massive power outage that affected millions of people, disrupting transport, communications, and daily life across the Iberian Peninsula. In this article, we’ll explain what happened, explore the possible causes, and look at the consequences of this rare and impactful event.
What Happened on April 28?
At around 11:33 a.m. local time (12:33 p.m. CET), a large-scale blackout hit much of Portugal and Spain. Cities like Lisbon, Porto, Madrid, and Barcelona were left without electricity. Metro systems, trains, and airports shut down, traffic lights stopped working, and mobile networks and the internet were affected.
In Lisbon, the metro stopped entirely, and the airport was closed around 1:00 p.m. Hospitals switched to emergency generators.
What Caused the Blackout?
The exact cause is still under investigation, but experts and national grid operators have outlined several likely factors:
1. Atmospheric-Induced Vibration
Portuguese grid operator REN pointed to a rare phenomenon called “atmospheric-induced vibration,” where strong winds can cause transmission lines to oscillate at specific frequencies. If these vibrations match the natural frequency of the lines, it can lead to equipment failures or automatic shutdowns to protect the grid. This is believed to be one of the main triggers.
2. Instability in the European Power Grid
Spain’s grid operator REE noted “strong oscillations” in the European electricity system, leading to Spain’s temporary disconnection from the continental grid and a domino effect of power station shutdowns. This type of instability can escalate quickly across interconnected networks.
3. Equipment Failure or External Events
There were early reports of a fire in southern France that might have affected power lines supplying Spain and Portugal. However, the French grid operator RTE later denied that any such fire occurred in the area.
4. Cyberattack? Unlikely.
Some media speculated about a cyberattack, but both Spanish and Portuguese officials stated there is currently no evidence to support this theory.
How Long Did It Last?
Power was gradually restored over the next few hours. By 11:00 p.m., about 51% of Spain’s electricity demand was met again. By 7:00 a.m. the next day, the grid was operating at 99.95% capacity. In Portugal, the recovery was similar, though REN warned it might take several days to stabilize the system fully.
What Can We Learn?
This incident revealed the vulnerability of modern electricity grids—especially as renewable energy sources, which are less predictable, become more prominent. It underlined the importance of investing in infrastructure upgrades and real-time monitoring systems to prevent and manage such large-scale disruptions.
The April 28 blackout was a rare and serious event. While the official investigation continues, initial findings point to a combination of rare atmospheric conditions and grid instability. It serves as a reminder of the fragility of our power infrastructure and the need for constant vigilance and investment to ensure energy security in the future.
