ENTSO-E final report: Iberia's 2025 blackout was triggered by over-voltage, not solar share
Europe's worst outage in 20 years stemmed from voltage-control gaps and cascading disconnections, clearing renewables of the headline blame
Summary
ENTSO-E released its final report on 20 March 2026 into the 28 April 2025 Spain-Portugal blackout, the worst in Europe in two decades, leaving 50+ million without power for up to 16 hours. The panel concluded the trigger was excessive voltage, not a supply shortage: it was "the first known blackout caused by over-voltage." Causes interacted , voltage oscillations, reactive-power-control gaps, divergent regulation practices between operators, rapid output reductions and generator disconnections in Spain, and uneven stabilisation. The findings reject the "too much solar" narrative; the report notes too few thermal plants were online to provide voltage control, and some renewable generation tripped as the system destabilised.
By the numbers
- 28 April 2025, the blackout; 20 March 2026, final report release.
- 50+ million, people who lost power.
- Up to 16 hours, longest restoration time in parts of Spain (12 in Portugal).
- First, over-voltage-triggered blackout of this scale on record.
Why it matters
The verdict reframes the policy fight: the risk in renewable-heavy grids is not generation share but the loss of voltage and reactive-power services as synchronous thermal units retire. It pushes operators toward grid-forming inverters, synchronous condensers and tighter cross-border voltage coordination.
What to watch
- Regulatory mandates for voltage/reactive-power services from inverter-based resources.
- Whether other high-renewable grids (CAISO, Australia) tighten voltage rules.
- Spanish and Portuguese operator-coordination reforms.