On a mild, sunny Monday in late April 2025, the power grids of Spain and Portugal collapsed in less than 90 seconds. At 12:33 p.m. Central European Summer Time (CEST), more than 50 million people lost electricity in what the investigating Expert Panel called "the most severe and unprecedented blackout that had occurred in Europe in the past 20 years." Portugal went dark for up to 12 hours; Spain for as long as 16 in some regions. A small area of southern France was briefly affected, though the rest of Continental Europe escaped unscathed.

Nearly a year later, a 49-member Expert Panel—drawn from regulators and grid operators across the continent—has published its 472-page final report, building on an earlier factual report released in late 2025. The document is exhaustive, technically dense, and notable for what it concludes: this was not the result of a single failure, but of many interacting weaknesses that converged catastrophically on a single spring afternoon. Here are the essential takeaways.