One year ago, shortly after noon on a mild spring day across the Iberian Peninsula, the electric grid collapsed. There were no dramatic satellite photos of a black void in a sea of light since grid service had been restored in many areas by nightfall, but that does not diminish the seriousness of the event.

As many as eight deaths were attributed to the blackout and critical services were unavailable for many hours. A year on, both the causes and learnings are becoming clearer and should inform policy, regulation and system operation, in Iberia and elsewhere.

Rush to judgment

In the immediate aftermath, the public square was flooded with explanations. Claims ranged from the fantastical (an “atmospheric phenomenon”) to the seemingly authoritative (a shortage of what’s called “system inertia” to manage grid frequency), all of them pure speculation. Some — especially those opposed to the energy transition — quickly seized on the fact that Spain and Portugal have become more reliant than most of their European neighbors on wind and solar generation. Indeed, at the time of the blackout about 70% of electricity generated on the peninsula was from wind and solar PV. Today we know nearly everyone was wrong, most notably those trying to hang the blame on renewables.

As weeks and months went by, data gathering and sober analysis began painting a picture both different from and more complex than what many initially envisioned. Take, for example, the theory about renewables and system inertia. Yes, the grid was heavily supplied by wind and solar at the time. And yes, Spain had very little battery storage and is weakly interconnected with the rest of Europe. Had the cause been inadequate system inertia, these factors would have been implicated. But it wasn’t. The amount of system inertia at the beginning of the event was within acceptable limits; frequency collapsed only in the latter stages as a consequence, not a cause of collapsing grid stability.

It turns out blaming the blackout on “too many renewables” was like blaming a loss by Real Madrid on having too many non-Spanish players on the pitch. The players were perfectly capable of winning the match, the fault lay in preparation, coaching, and strategy.

Complex machine, complex failure

If forced to name a single cause, most experts today would cite a failure to manage grid voltage within acceptable limits. While that is fair, it oversimplifies the matter. Many inter-related failures led to the collapse. Some were associated with fossil generators, some were associated with renewables, some were related to transmission, and some were baked in by regulatory and operational choices made long before.

For example, most renewables in Spain were not configured to support voltage control. This left grid operators with too few options when, among other developments, multiple fossil generators failed to perform as expected. But that was a choice. Renewables are capable of contributing to voltage management, and in other high-renewables grids they do so. In fact, Spain was scheduled to implement such a requirement later in 2025. If 70% of a grid’s generation is made unavailable for voltage management, no matter what kind of generation it is, such an event becomes more likely.

The modern continent-wide power grid is a complex machine. When it fails, the reasons can be equally complex, involving a rapid chain of failures. Typically, some events in the chain are entirely avoidable, others normally manageable, but taken together, they overwhelm the ability of system operators to keep the grid fully functioning. Real Madrid was capable of winning with the players on the pitch, but the strategy and preparation were flawed, and the coaches could not adjust in time.

Learning the right lessons from a serious event

Operating an electric grid reliably with a high share of renewables is at least as feasible as it is with a legacy high-carbon resource mix. But it is different. Every “failure” in this event that has been blamed on renewables can be traced to a failure to adopt what are becoming best practices — such as the voltage regulation practices that could have prevented the Iberian blackout.

We’ve learned over time, sometimes the hard way, to operate the grid reliably each time valuable new technologies or fuels were introduced; adapting to a high-renewables, low-carbon energy mix is no different. It requires planners, regulators, policymakers, and grid operators to learn and adopt best practices as those learnings become available.