Iberian Peninsula blackout proves the need for grid resilience

8 May 2025

Last week Spain and parts of Portugal had no electricity for hours. Many issues can cause a blackout as such. From transmission failures and extreme weather to cyberattacks. This major event stresses the need for grid resilience.

On Monday 28 April the Iberian Peninsula experienced a major power blackout, resulting in a complete outage of electricity supply. Around midday electricity demand and generation dropped sharply. Although the grid initially stabilized, another drop occurred just 1.5 seconds later. Seconds after that, the Spain–France interconnector tripped.

The disruption affected all major generation sources. Nuclear and coal plants completely shut down while wind and solar production dropped significantly as protection mechanisms activated to prevent damage. The renewable generation however rebounded quickly once conditions stabilised. Telecommunications, transport systems and critical services were disrupted. It took 23 hours to restore Spain’s grid to full operation.

What causes a blackout?

Several things can cause a blackout – from transmission failures and extreme weather to cyberattacks. The incident highlighted the delicate balance required to maintain grid frequency, which must remain close to 50 Hz across Europe. When this balance is lost, protection systems automatically disconnect generators and users to safeguard infrastructure. If this imbalance continues, it can trigger cascading failures.

The exact cause of the Iberian blackout is still unknown, and speculation continues. Initial data from Spanish grid operator Red Eléctrica de España pointed to unusual low-frequency oscillations between Iberia and the main European grid just before the outage.

Renewables were providing most of Spain’s electricity when the outage occurred – as they often do. On average, wind provides 25% of Spain’s electricity, solar also provides 25%. Some observers have suggested that low system inertia may have contributed to the outage. Inertia is the grid’s ability to keep the frequency stable. Traditional power plants provide inertia through rotating masses but wind and solar do not inherently provide this. With the right market incentives, wind farms can deliver different forms of grid support including voltage and frequency control and synthetic inertia.

So far, there is no evidence linking low inertia to the blackout. High-inertia systems have suffered similar failures, and Spain had recently operated on 100% renewables without problems. Many countries, like Denmark and Germany, successfully operate electricity systems with high levels of variable renewable energy by using advanced grid management, energy storage, and strong regional connections to maintain stability.

The wind sector urges caution and calls for a thorough, technical investigation. A full assessment by the relevant TSOs and ENTSO-E is essential to understand the event from a system-wide perspective.

Preventing future outages will require investment in smarter grids

We already various tools to reduce risks to stability in electricity system: power system stabilisers, synthetic inertia and grid-forming inverters. Grid operators are also turning to battery storage, synchronous condensers, and STATCOMs, as well as purchasing inertia through the market. Ireland and the UK are leading in this space. Irelands’ EirGrid runs a Low Carbon Inertia Services programme, while the UK’s National Energy System Operator (NESO) has Stability Pathfinder, which secures long-term contracts for stability services.

As renewables grow, we must fully use their stabilising capabilities through better market design. A balanced energy mix is vital for system stability. Wind power can and should play a leading role. Modern turbines can support frequency and voltage, and in some cases, provide synthetic inertia using the kinetic energy in their blades. Hybrid projects that combine wind, solar and storage offer even more flexibility and resilience.

Regulations and market structures also need to evolve. Policymakers should encourage large-scale energy storage and co-located renewable projects where wind and/or solar and/or storage operate together. Flexibility markets and demand response must become standard practice. Boosting cross-border interconnection capacity, especially between Iberia and the rest of Europe, will also help reduce the risk of regional blackouts.

This incident highlights a key lesson. To meet its climate and energy goals, Europe must speed up renewables and invest in stronger, smarter electricity grids and more energy storage. Upgrading, expanding and digitalising the grid is key to keeping energy secure and affordable – and to building a more competitive European economy.

WindEurope’s CEO Giles Dickson said: “We need to invest urgently in grid resilience, smart infrastructure and energy storage. Renewables are not the problem – they’re part of the solution. With the right tools and market design, they can help keep the lights on and Europe competitive.”