Earlier this year, tens of millions of people in Spain and Portugal were plunged into darkness, some for up to 10 hours. The blackout—which happened in just five seconds on 28 April—cut off power to key services and infrastructure across both countries, leaving an estimated 15-gigawatt (GW) hole in electricity supply, the equivalent of losing the electricity needed to power 15 million homes all at once. It was one of Europe’s worst blackouts in decades and left hospitals running on generators, trains halted, and supermarkets shut.1
In the aftermath, many questioned whether renewables were responsible for the blackout, pointing to their intermittency. While this criticism has some merit, it is ultimately flawed. Below we outline why this is the case and discuss how Europe’s largest blackout in decades could spur new investment opportunities globally.
Initially, some assumed the blackout was caused by a lack of supply. Perhaps winds weren't blowing, or clouds engulfed the skies of Spain and Portugal, preventing sunlight from reaching solar panels. But according to the Spanish grid operator, in the period running up to the blackout, the Spanish grid was being supplied with 32GW of power, comfortably outstripping the population demand of 25GW,2 meaning that the excess power was either stored or exported to Portugal, France and Morocco.3 During this time, more than 75% of supply was from renewables and electricity prices were negative,4 so clearly the supply of renewable energy was not the contributing factor.
So what did happen? The root cause of the blackout was a combination of the grid operator not effectively managing the voltage within the system, thermal power plants not performing as they should and a substation failure. This series of small events created a snowball effect which shut down the entire system, like having a faulty appliance in a house that trips out the whole house to protect everything else in the system. This is what effectively happened in Spain and Portugal, but on a much larger scale.
The reality is, electricity grids, which provide power across countries and continents, are temperamental. There needs to be a fine balancing between supply and demand throughout the day to maintain stable levels of frequency and voltage in the grid. This inevitably means that renewables—which have volatile supply—create more fluctuations in grid frequency and voltage. The issue arises when the frequency or voltage becomes too volatile or too low. The generators then disconnect to protect themselves and the overall grid, creating a cascading effect where in just a few seconds, vast amounts of supply disappear.
Over types of energy sources, such as thermal plants, coal and gas, offer “inertia”—the ability to maintain a steady output of power despite fluctuations—and act fast to inject additional supply into the system. It’s like driving a car down the motorway when the engine stalls. The car doesn’t grind to a stop instantly. It keeps moving but slows down, providing plenty of time to restart the engine and carry on before the speed drops too much. Renewables however cut out almost instantly, with little to buffer the shock.
Does this mean wind and solar are unsuitable in the long term? Certainly not. These technologies are cheap and quick to deploy and therefore will continue to attract investment to meet growth in electricity demand for the foreseeable future. Luckily, the solutions to balance the intermittency—which include batteries—already exist, and the cost of deploying them has fallen dramatically as investment rises. Battery Energy Storage Systems (BESS) are large batteries that store electricity for later use and help stabilise the grid. Crucially, not many are needed to help maintain grid stability and prevent blackouts. They can also discharge instantaneously, which means when there’s a sudden demand for electricity or a shortfall in a grid, the BESS can provide power immediately.
The UK has already built far more of these battery storage systems than is required to provide stability in the British grid. It’s a different story in Spain, however. Spain lags significantly behind in producing these battery storage systems, leading to continued reliance on thermal generation for grid stability. Even though renewables weren’t the root cause of the blackouts, they could well be a source of future vulnerability if these buffers aren’t built into the system.
Renewables are critical to meeting existing and future energy needs but come with well-known challenges. Maintaining grid stability and matching supply and demand are crucial. Solutions to these challenges exist, are proven and have already been scaled in countries such as the UK. Spain has already committed €700 million to accelerate the build out of battery storage.5
Grid modernisation and energy storage are exciting investment opportunities that we continue to explore. As the world transitions to low carbon alternatives for power generation, the blackouts in Spain and Portugal underscore the need to restore and modernise these grids globally.
Energy systems are incredibly complex, and when such events occur, it is important to analyse the situation rationally and with care. This helps prevent false narratives shaping our views on low carbon technologies and reminds us of the broader investment opportunities in the global transition to a lower-carbon energy system.
[1] NYTimes: Spain Searches for Answers on What Caused Power Blackout
[2] 2025 Iberian Peninsula blackout
[3] The Conversation: Spain-Portugal blackouts: what actually happened, and what can Iberia and Europe learn from it?
[4] The Conversation: Spain-Portugal blackouts: what actually happened, and what can Iberia and Europe learn from it?
[5] Energy-Storage News: Spain launches €700 million support scheme for energy storage
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