Why Did the Massive Blackout Hit Spain and Portugal?

On Monday, April 28th, 2025, an unprecedented and historic event occurred in Spain and Portugal:
At 12:30 PM, the entire country lost power — and with it, the internet (except for those using satellite connections).

For hours, both countries were essentially “switched off.” People couldn’t even find out what was happening, since they had no access to the internet. Around six hours later, power slowly began returning in some regions, and by the end of the night, it was mostly restored across the country.

But now, four days later, the big question remains: What caused the blackout to affect the entire country for so many hours?

So far, the Spanish government hasn’t given a clear answer. At first, there were rumors of a cyberattack, but that theory now seems less likely.

So… what happened?

Here at CleverDebates.com, we like debates — but always based on data, with the highest reliability possible (if you spot an error, let us know and we’ll update it), and presented in a simple, clear way.

In this blackout case, the fact that there’s still no official explanation after four days suggests that the answer is not simple.
However, let’s focus on one particularly interesting data point:

The blackout began at 12:30 PM, and as seen in the chart, something curious was happening at that time —
Of all the energy being produced in Spain at that moment, over 80% came from renewable sources (67% solar, 13% wind).
That was near a record — and ironically, it seems like this high reliance on renewables may have destabilized the entire system.

Unlike nuclear energy, renewables are much more unstable by nature. Strangely, it appears that nuclear plants were shut off at that moment, removing the stabilizing layer they usually provide — the kind of “cushion” that protects the grid during fluctuations.

These nuclear plants may have been disconnected because energy prices were so low that it was no longer economically viable for them to stay online. But removing that cushion may have triggered the collapse.

An Energy Island

Another issue for Spain and Portugal is that they’re somewhat of an “energy island” — connected only to France and Morocco,
while other European countries are deeply interconnected with neighbors.
Those interconnections act as stabilizers, helping to balance supply and demand.

When supply and demand fall out of sync, and grid tension isn’t maintained, the entire system can crash — and shut down, which is exactly what happened. Spain’s Prime Minister, Pedro Sánchez, said that “15GW disappeared in 5 seconds” — raising the question:
Did that drop come from nuclear sources, or elsewhere?

In the table below (source), you can see a breakdown of Spain’s energy production at the time of the blackout.

Type	MW (%)
Solar PV	18283 MW (66.77%)
Wind	3645 MW (13.31%)
Hydro	202 MW (0.74%)
Nuclear	3389 MW (12.38%)
Gas	1633 MW (5.96%)
Coal	230 MW (0.84%)

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What do you think happened? Let us know in the comments!