On April 28, 2025, a massive power outage swept across the Iberian Peninsula, plunging Portugal, Spain, and parts of southwestern France into darkness for up to ten hours. As Thailand advances its energy transition by increasing renewable integration and regional interconnections, the European blackout serves as a stark reminder of the grid vulnerabilities that still exist.

This article marks the first installment of From Crisis to Clarity, a three-part series analyzing the recent European blackout and its implications for Thailand. In this article, we examine the root causes of the outage in the Iberian Peninsula. The second article will assess the likelihood of a similar event occurring in Thailand, considering the country’s current energy infrastructure and its increasing reliance on renewables. The final article will present key lessons and recommendations that Thailand can adopt to strengthen its energy system and prevent comparable disruptions in the future.

Root Causes of the European Power Outage

At approximately 12:30 p.m. on April 28, 2025, Spain experienced a sudden and severe drop in electricity generation, with output falling from around 27 gigawatts to slightly over 12 gigawatts. While investigations are still ongoing, preliminary reports suggest a cascading failure triggered by a fault in a high-voltage cross-border transmission line. The abrupt and precipitous drop in supply created significant instability in the national grid, which relies on maintaining a constant frequency of 50 hertz to ensure operational balance. The resulting frequency deviation triggered automatic safety systems. As a result, some power plants, including nuclear plants, were disconnected. This also led to the disconnection of the interconnection line between Spain and France via the Pyrenees. Ultimately, these events caused a complete collapse of Spain’s power system for up to ten hours.

Speculation persists about the exact cause of the Iberian blackout. While Spanish authorities have ruled out a cyberattack, one possible contributor is a lack of so-called “grid inertia”—the property of a power grid that enables it to resist changes in frequency, typically provided by the rotating mass of conventional generators. In other words, grid inertia is the grid’s ability to keep the frequency stable. Traditional grids powered by gas and nuclear plants have high inertia, making them more resistant to frequency changes. In contrast, grids with a high share of renewables, such as wind and solar, have low inertia unless specific measures are taken to compensate.

On May 1, 2025, the Association of European Transmission System Operators (ENTSO-E) announced the establishment of a panel of experts tasked with conducting a thorough inquiry into the causes and consequences of the blackout. This panel is expected to deliver a final report within six months of the incident. Interim publications, including event analyses, developing conclusions, and recommendations, are scheduled to be released at the end of each two-month period following the incident, providing updates on the investigation’s progress. Spain and Portugal have been given three months to submit their data, reflecting the complexity and scale of the event.

Takeaways

The recent European blackout demonstrates how quickly low-inertia power systems can spiral out of control when frequency stability is compromised. This scenario is increasingly relevant to Thailand, whose traditionally gas-based, centrally managed grid still benefits from a buffer of rotational inertia but is rapidly integrating renewable energy sources and expanding interconnections with neighboring countries. As Bangkok looks toward a future where renewables may account for more than half of installed capacity, the Iberian lesson highlights that strengthening and enhancing the reliability of the grid are no longer optional.

For more on this topic, read the second article in the series: “Could a Similar Outage Happen in Thailand?”