ENTSO-E, the European Network of Transmission System Operators for Electricity, has published its factual report, which presents facts and data on system conditions during the Iberian Peninsula blackout of April 28, 2025, as well as a detailed sequence of events.

The report does not blame renewable energy sources or an excess of them for the incident . The report does not identify inertia problems during the day of April 28, but it does point to some significant problems in controlling the voltage of the electrical system. 

The report highlights that existing voltage control mechanisms were unable to handle voltage fluctuations on April 28. 

In these voltage control mechanisms, renewable energy sources were unable to participate to help stabilize the grid, as they had been requesting for years, because the operating procedure governing this mechanism (PO 7.4) was not updated. 

Following the blackout, an update to this procedure was urged to allow renewable energy sources to contribute to voltage control. This update finally took place on June 12, 2025. 

“ The full implementation of this procedure, which will still take several months, will allow for a more robust and better-prepared system to prevent these types of incidents. The participation of renewable energy, and especially photovoltaic energy, in this voltage control will also lower electricity prices and reduce CO2 emissions from power generation ,” comments José Donoso, director general of the Spanish Photovoltaic Union (UNEF).

Operation of conventional generation that was subject to power outages on April 28 in Spain and Portugal. Source: “Grid incident in Spain and Portugal on April 28, 2025” ENTSO-E