Spain Unplugged: When the Grid Went Down

At around 12:30 p.m. on April 28th, a massive blackout hit Spain and Portugal, affecting 55 million people; this is Europe’s biggest blackout in 20 years. Internet connection, traffic lights and trains all stopped working; hospitals were running on generators. 

Photo credit: Thomas Coex 

How did this happen? 

The exact cause is still unclear, but the Portuguese grid operator, REN denied claiming extreme weather caused the blackout and the Portuguese government ruled out cyberattacks. At the time the blackout hit, the demand was at normal levels and was able to be met by the total generation capacity. Around 80% of the electricity was generated through wind and solar, though renewables are intermittent, the volume of renewable is not likely the cause of outage of this scale. 

At 12:30, the price of electricity was at around -1€/MWh. Spain was exporting electricity to Morocco, Portugal, and France, also pumping water into reservoirs to store energy. Between 12:30 and 12:35m several unusual events were observed in the Spanish National Grid- REE’s data that deepened the imbalance between supply and demand, including: 

• A spike in wind power generation

• A sharp drop in solar generation from 18,000 MW to 8,000 MW within seconds

• France suddenly stopping electricity imports from Spain

Beyond the supply-demand imbalance, a key factor was low grid inertia. Gas and nuclear-powered electricity grids create electricity through spinning turbines, which help maintain grid frequency at around 50Hz. Renewable grids, by contrast, have low inertia, meaning they are less able to resist sudden changes and are harder to stabilize during disturbances. This makes them more vulnerable to cascading failures when disruptions occur.

However, this weakness can be mitigated. Battery storage systems and other grid-stabilizing technologies can provide critical "breathing space" by reacting instantly to frequency drops and helping operators restore balance.

The grid we rely on today was designed for a slower, more predictable world. To effectively integrate large-scale renewable energy, utilities need to invest in adequate physical capacity, real-time monitoring, and smarter, more adaptive network management. 

Within hours of the blackout, the French grid operator supplied 900 MW of electricity to help restore power to the Iberian Peninsula, but it was not until almost 23 hours later the Spanish electricity grid declared that it’s back to normal. The event was a wake-up call for Europe’s energy future.