On 28 April 2025, large parts of Spain and Portugal experienced a sudden and widespread power blackout. Within hours, speculation began to circulate: had the country gone “too far” with renewables? Was this the downside of phasing out fossil fuels?

These questions are increasingly common, but they often oversimplify. The blackout followed a series of grid disturbances over just five seconds, causing the grid frequency to drop and leading to the shutdown of a key interconnector near the French border. This triggered cascading effects: sharp frequency imbalances, voltage oscillations, and the automatic disconnection of nearly all power sources to protect the system.

This wasn’t an isolated anomaly. It was a stress test – the kind Europe’s grids will face more often as electrification advances, especially with climate change intensifying short-term temperature swings. The question isn’t whether the energy transition should continue, but whether we’re investing fast enough to keep the system stable as it evolves.

1. The grid is now central to the energy transition – and underfunded

The International Energy Agency (IEA) estimates that global grid investments need to double by 2030 – from roughly USD 300 billion to over USD 600 billion per year – to meet national climate goals. This is not just about adding capacity. It’s about building smarter, faster, and more flexible systems that can accommodate the rapid growth of variable renewables, electric vehicles and heat pumps. The IEA warned in October 2023 that “[l]ack of ambition and attention risks making electricity grids the weak link in clean energy transitions”.

Spain’s blackout exposed what happens when that flexibility is missing. There was not enough fast-response capacity to stabilize frequency imbalances as they emerged. Power systems have long relied on inertia from big spinning generators to keep frequency stable during disturbances. As more wind, solar and batteries connect to the grid, that traditional inertia is reduced. But modern batteries and inverter-based technologies can respond to problems much faster than old systems. This fast-frequency response helps keep the grid stable – even with less inertia.

One largely untapped resource is the growing fleet of electric vehicles (EVs). Vehicle-to-grid (V2G) systems allow EVs to supply electricity back to the grid during moments of instability. Public bus fleets, for example, are ideal candidates: they have large batteries, predictable schedules and centralized depots. In theory, V2G could significantly expand system resilience. In practice, V2G uptake remains minimal. Without clearer standards and incentives – and with sluggish EV adoption – the opportunity remains largely untapped.

2. Cross-border interconnections are a critical weak point

Spain and Portugal are connected to the rest of Europe via a single major interconnector – a 2.8 GW line that failed during the blackout. This made the system more fragile and it underscores how interconnections, often viewed as long-term infrastructure investments, are actually central to short-term stability. The cross-border capacity ratio (i.e. the electricity exchange capacity with other countries compared to the total installed power) between the Iberian peninsula and the rest of Europe is just 2%. The Spanish Transmission System Operator (TSO) characterizes this as low, since the European Council set a target for an interconnection level of at least 10% by 2025 and 15% by 2030 with the rest of the EU.

The importance of strong interconnections was also clear in the blackout recovery phase. France and Morocco supplied emergency electricity to help stabilize the system, feeding power into Spain through lines connecting Catalonia, the Basque Country and across the Strait of Gibraltar. At the same time, renewables played a critical role: pumped-storage hydropower, in particular, provided fast-start capacity that helped kick off the black start process when other plants, like nuclear, were unavailable.

In an electrified Europe, stronger interconnections allow countries to share reserves, manage variability in supply and demand, and stabilize prices. But projects move slowly. Permitting, funding, and coordination are all bottlenecks, which the European Commission is trying to solve with the EU Action Plan for Grids – but we’re not treating them with the urgency we should.

3. Resilience means preparation, not perfection

It’s tempting to ask whether the blackout could have been prevented. But blackouts are not new – they occurred in the fossil era too, e.g. in Italy and Switzerland in 2003 due to a fallen tree causing an electrical arc, or in Sweden the same year due to a geomagnetic storm. The N-1 rule – which ensures that the grid can withstand the failure of a single component without widespread disruption – is a core principle of energy system security. But cascading effects, like those seen during the Spanish blackout, can overwhelm this safeguard when multiple stresses interact in rapid succession.

That’s a reason to focus more seriously on resilience, especially since such sudden, large-scale power losses (some sources estimate 60% lost in seconds) are not common enough to justify building the grid to avoid them entirely. So we have to focus on how to manage these rare events.  Are there clear plans for when things go wrong? Are reserves ready, and roles understood across operators and authorities? These are governance questions as much as technical ones.

Resilience also has a public dimension. As electricity powers more of daily life, the impact of outages grows – yet public preparedness is often overlooked. Strategies must include vulnerable groups, social services and effective communication.

Some previous examples of targeted support for vulnerable groups during power outages can serve as inspiration. In California, the Self-Generation Incentive Program offers battery storage subsidies, with extra support for low-income and medically dependent residents. Puerto Rico has established solar-powered resilience hubs at clinics and community centres, ensuring backup power for essential services. In the UK, the Priority Services Register gives at-risk individuals advance outage warnings and priority reconnection, helping utilities respond to those most in need.

To sum up: the Spanish blackout isn’t a sign that we’ve gone too far with renewables. But it is a sign that we haven’t done enough to support the transition.

If we want secure, low-carbon, electrified societies, we need more than just clean generation. We need grid investment, more grid flexibility through batteries and V2G, cross-border coordination and a more realistic understanding of what resilience really takes.

Technical failures will happen. The question is whether we’re ready for them.