Final ENTSO-E report sheds light on 'multiple factors' that caused Iberia blackout

Read the full article here.

The European Network of Transmission System Operators – Electricity (ENTSO-E) has released its final report on the causes of the blackout that wiped out the power grids in Spain and Portugal on 28 April 2025.

According to the report, the blackout resulted from a combination of many interacting factors, including oscillations, gaps in voltage and reactive power control, differences in voltage regulation practices, rapid output reductions and generator disconnections in Spain, and uneven stabilisation capabilities. 

These factors led to rapid voltage increases and cascading generation disconnections, resulting in the final blackout event.  

Although renewables were not widely referenced in the recommendations, the report does highlight the sensitivity of small-scale PV generation to high-voltage episodes, even when transmission-side voltage remains within acceptable limits. 

The data that ENTSO-E’s Expert Panel received from PV system manufacturers during the investigation showed that many inverters tripped due to overvoltage during certain periods on 28 April. The panel also identified an important role of the reconnection time of the non-observable PV systems in the loss of generation.

Source: ENTSOE-E