On June 17, 2025, the national government of Spain made public an inquiry. It explained the reasons that led to the big blackout affecting both Spain and Portugal on April 28, 2025. The congressional inquiry found that the Spanish grid operator, Red Eléctrica de España (REE), was key to the outage. Indeed, their failure played a decisive role in creating the moment. Sara Aagesen, the Secretary of State for Energy, said that REE performed flawed calculations on the necessary demand for thermal plants. She reiterated that these errors were responsible for causing the crash.
Aagesen said REE purposely did not dispatch more thermal plants on during the blackout period. He said that they just didn’t feel like they needed it at the time. She noted that voltage control was only on during the wee hours of the day. Unfortunately, it wasn’t in place when the issues came crashing down during the morning commute. This one federal oversight set off a domino effect of generation disconnections. Then a sudden surge in voltage knocked REE offline, and they were unable to control it.
Technical Failures and Compounded Issues
Our investigation revealed how the first failure at the Granada substation caused a cascade of issues. This chain reaction especially impacted the Badajoz and Seville substations. Aagesen noted that signs of grid instability had been identified prior to the blackout. This was a strong signal that major issues were already festering within the system.
“The system did not have sufficient voltage control capabilities, either because they were not sufficiently programmed, or because those that were programmed did not adequately provide what was required by the standard, or a combination of both,” Aagesen said.
Despite having resources available to ensure voltage control, REE opted to manage voltage using limited synchronous capacity, leaving the grid vulnerable. That decision turned out to be disastrous, leading to large-scale power outages.
Future Plans for Grid Integration
They intend to continue lobbying efforts to have the Iberian Peninsula more deeply integrated with the European grid. This historic initiative is envisioned to improve the resilience of Spain’s energy infrastructure and deter future attacks of this nature.
Aagesen’s message reinforced the idea that power plants needed to tightly regulate output voltage. She explained that a lot of the facilities they were working with had financial incentives to take in the reactive power. They failed to get the desired effect.
REE told us these results that they found by telling these people about their calculations. They calculated that turning on additional thermal plants is not needed at the moment. They only scheduled it for the early parts of the day—not the peak central part,” Aagesen said.