The Day Spain and Portugal Went Dark: Causes of the Blackout and Lessons for Canada

On April 28, 2025, a massive power blackout plunged tens of millions of people across Spain, Portugal, and parts of France into darkness. Cities like Madrid, Barcelona, and Lisbon ground to a halt as trains, metros, traffic lights, ATMs, and phone networks all failed without warning. In one chaotic midday moment, hospitals switched to emergency generators, airport operations faltered, and thousands found themselves trapped in elevators and subway tunnels lit only by cell-phone flashlights. Outages on such a scale are extremely rare in Europe, and governments in Spain and Portugal raced to manage the crisis and uncover what went wrong.

What Happened During the Blackout?

Commuters navigate a darkened Madrid metro station during the April 28, 2025 blackout. Emergency lighting is minimal as people exit the turnstiles into a corridor with no power. The Iberian blackout struck suddenly late Monday morning. At 12:33 p.m. local time, power failures cascaded across most of Spain and all of Portugal (with brief spillover into southwestern France). The Spanish grid operator Red Eléctrica de España (REE) later nicknamed the event “el cero” – “the zero”, referring to a total collapse of the electric system. In minutes, nearly half of Spain lost electricity, leaving major cities and regions without supply. Public transport was paralysed as rail operator Adif halted all trains nationwide and metro systems in Madrid, Barcelona, Lisbon and Porto ground to a stop. Traffic signals went dark, causing gridlock until police and even civilians stepped in to direct traffic at intersections. Daily life was utterly disrupted – an estimated 35,000 rail passengers had to be rescued from stranded trains, and hundreds of people were stuck in jammed elevators across the peninsula.

Authorities responded with emergency measures. Spain’s interior ministry declared a national emergency and deployed 30,000 police officers to maintain order. Both Spain’s Prime Minister Pedro Sánchez and Portugal’s Prime Minister Luís Montenegro convened crisis meetings as power companies began the painstaking work of a “black start” – rebooting the grid from scratch. By mid-afternoon, engineers slowly started restoring service, first re-energizing pockets of the north (the Basque Country) and Catalonia, then portions of Madrid by evening. Progress was cautious to avoid overloading lines as each generator and substation reconnected in sequence. Even by 10:00 p.m., however, nearly 40% of Spain’s demand was still unmet (only 43% of power need was being served), and large parts of Portugal remained offline. Full power supply wasn’t restored until the early hours of the next day, making this one of Europe’s biggest-ever power system collapses since the 2003 Italy outage and a 2006 continental blackout incident.

The immediate impacts underscored modern society’s dependence on electricity. Internet traffic plummeted by 80–90% in the affected countries during the outage. Supermarkets in Madrid saw long queues and shelves emptied as people panic-bought essentials. In one striking scene, play at the Madrid Open tennis tournament was suspended mid-match as the lights went out. Yet amid the chaos, there were moments of calm improvisation: many Spaniards simply took an unexpected half-day off, gathering in plazas or cooking meals by candlelight at home. While back-up systems prevented total disaster in critical services (banks switched to battery systems, and hospitals kept urgent care running on generators), the April 2025 blackout will be remembered as a startling reminder of how swiftly daily life can be upended when the grid goes down.

Searching for Answers: What Caused the Blackout?

As lights flickered back on, experts began the forensic hunt for what triggered this unprecedented collapse of the Iberian grid. Early on, speculation swirled about possible causes – from a cyber-attack or sabotage, to instability from Spain’s huge renewable energy output, to freak weather phenomena. Governments were cautious not to jump to conclusions. Spanish grid operator REE ruled out a cyberattack on its systems, yet Prime Minister Sánchez noted that absence of evidence didn’t entirely preclude foul play. Spain’s National Security Council met to assess any security threat, but both the European Council President (former Portuguese PM António Costa) and EU officials confirmed there were “no indications” of a deliberate attack. In short, a malicious actor was not believed to be behind the blackout.

Increasingly, the focus turned to technical factors and the stability of the electric grid itself. By Tuesday, REE had identified a sequence of events that likely led to the collapse. According to preliminary data, there were “two incidents of power generation loss” – probably involving large solar photovoltaic plants in southwestern Spain – which occurred shortly before the outage. These sudden drops in generation upset the equilibrium of the system and led to a breakdown of Spain’s main transmission link with France. In fact, between 12:30 and 12:35 p.m. local time, solar power output in Spain plunged by more than 50% – plummeting from over 18 gigawatts to just 8 GW. This enormous loss of supply (cause still unknown – possibly a technical fault or abrupt weather change) sent the grid frequency nosediving below the safe 50 Hz level. Grid frequency in Europe must be kept tightly around 50 Hz; any large deviation triggers automatic safety mechanisms that disconnect generators and equipment to prevent damage. And that is exactly what happened – a cascading failure.

Pedro Sánchez described the event in stark terms: Spain’s grid lost 15 GW of generation in just five seconds – about 60% of the country’s entire demand at that moment. The shock was more than the system could handle. Protective relays began tripping generators offline in rapid succession as frequency fell. This included not only plants in Spain and Portugal, but even a power station in France that sensed the disturbance and shut down. Crucially, the high-voltage interconnection with France (Spain’s main link to the broader European grid) disconnected amid the chaos. Spain had been exporting power to France and Portugal just before the incident; in fact, exports to France were near capacity, about 0.87 GW, until they abruptly dropped to zero at 12:35 p.m.. When the tie to France broke, the Iberian Peninsula became an electrical island with a massive supply-demand mismatch, causing the entire Spanish-Portuguese system to collapse in what engineers call a “black system” event.

Notably, weather was largely ruled out as a primary cause. The skies were clear and calm across Spain that day – no storms, no lightning strikes, none of the usual culprits like wind or ice that commonly knock out power lines. There was an early rumor (attributed to Portugal’s grid operator REN) blaming a “rare atmospheric phenomenon” – extreme temperature fluctuations causing vibrations in transmission lines. Sudden heating or cooling can indeed make wires sag or oscillate and potentially trip circuits. However, REN later disowned that explanation as a misquote, and electrical engineers expressed skepticism about such an exotic scenario being solely responsible. One expert noted that the term “induced atmospheric vibration” is not widely recognized in power engineering and would be an unusual, perhaps unprecedented, trigger for a nationwide blackout. While investigators haven’t completely ruled anything out yet, the emerging consensus is that a combination of grid factors – likely a large, sudden loss of generation in a system operating with low inertia – set off the chain reaction.

Indeed, one critical factor was the structure of Spain’s energy mix at the time of the outage. Around midday, Spain’s electricity was coming predominantly from renewable sources – about 59% from solar PV and 12% from wind, with only around 11% from nuclear plants and a mere 5% from gas-fired turbines (and minimal coal). This meant the grid was running with very low inertia. Inertia is the stabilizing energy stored in the spinning masses of big generators (like turbines in gas, coal, or hydro plants) that helps buffer sudden changes in supply or demand. Solar farms, by contrast, don’t inherently provide that rotational inertia. So when the solar output crashed and the frequency dipped, there was little spinning reserve to slow the plunge. The result was that protective systems tripped extremely fast across many plants. As one analyst put it, the “cascading disconnections” of power stations occurred as the grid frequency fell out of bounds, turning a local disturbance into a peninsula-wide blackout in seconds.

European authorities have launched a thorough investigation into the incident, and it will likely take time to pinpoint the exact initiating failure. But already, the April 2025 blackout is highlighting important lessons and sparking debate about grid stability in an era of cleaner energy.

Does the Blackout Reveal Risks in the Net-Zero Transition?

The Iberian blackout has prompted a hard look at how the push for net-zero emissions and rapid renewable energy growth might affect grid reliability. Spain has been a leader in renewable power – in 2022, 56% of its electricity came from renewable sources, and it aims for 81% by 2030. This green shift greatly reduces carbon emissions and reliance on imported fuels, but it also “brings its own challenges”, as The Guardian noted, particularly the need to upgrade grid infrastructure and balancing systems for a new era of decentralized, weather-dependent generation. Every national grid undergoing decarbonization will need significant investment to connect widely scattered solar and wind farms and to keep the supply and demand in constant equilibrium.

Critics and proponents of renewables are debating the implications of the outage. Some wondered whether the blackout is evidence that variable solar and wind make the grid more fragile, prone to swings and instability. For example, when bright midday sun suddenly vanished behind clouds (if that indeed happened) and output plunged, the system couldn’t compensate quickly enough. However, officials have been cautious about drawing easy conclusions. Prime Minister Sánchez strongly rejected claims that “excess renewable energy” was to blame, pointing out that at the moment of the blackout, electricity demand was relatively low and there was actually ample generation available on the system. In other words, it wasn’t a lack of megawatts that caused the collapse, but a lack of balance in the split-second dynamics of the grid. The EU Energy Commissioner, Dan Jørgensen, echoed that sentiment, saying the cause “cannot be reduced to any particular source of energy”.

Grid operators note that even fully fossil-fueled grids can suffer blackouts if not engineered properly – major outages have occurred in systems dominated by coal or nuclear in the past. “It doesn’t matter where you are getting the energy from; you’ve got to get the engineering right to ensure resilient electricity supplies,” emphasizes Dr. Keith Bell, an electrical engineering professor. In Spain’s case, there was indeed plenty of conventional generation (nuclear, hydro, gas) online prior to the event to theoretically cover the loss. The blackout appears to be less about the presence of renewables per se, and more about real-time coordination and stability tools lagging behind the rapid transformation of the resource mix.

That said, the incident is a wake-up call about specific technical vulnerabilities that can accompany a rush to net-zero. One issue is the low inertia scenario, as discussed – a grid with too few spinning turbines can react too violently to a sudden perturbation. Another issue is managing periods of surplus renewable power. Europe’s renewable boom has at times flooded grids with excess electricity during sunny, low-demand hours, driving wholesale prices negative and forcing curtailment of solar farms. Spain and Portugal were already expected to see a rise in hours where renewables exceed demand in 2025. If not managed, such conditions can lead to complex control challenges. Modern solutions – like large-scale batteries, flywheels, synchronous condensers (spinning machines that provide inertia without generating power), and advanced power electronics – are all available to help keep a renewable-rich grid stable. But deploying these at the pace of renewable expansion is crucial. “You cannot ignore it – you need the tools to keep the system running,” warns Georg Zachmann of the Bruegel think tank, referring to frequency control in the age of solar and wind.

In sum, the blackout underscores that achieving net-zero energy goals must go hand-in-hand with investing in grid resilience. The transition to clean power is essential to mitigate climate change (and Spain’s leadership in green energy remains commendable), but this event shows the importance of the “boring” infrastructure and coordination behind the scenes. Europe will be drawing lessons from the Iberian incident – and so should other countries with big climate ambitions.

Could This Happen in Canada?

For Canadians watching the news of Barcelona and Madrid going dark, an obvious question arises: Could such a massive blackout happen here? Canada’s grid is generally very reliable, and the country already produces roughly 85% of its electricity from non-fossil sources (mostly hydroelectric, plus nuclear and wind). But large-scale blackouts are not unheard of in North America. In August 2003, a cascading failure in the northeastern US and Ontario caused a historic blackout that left over 50 million people without power for at least 24 hours, including major Canadian cities like Toronto and Ottawa. More recently, extreme weather events have tested grid limits – for example, a deep freeze in Texas in 2021 knocked out power to millions (as generation of all types failed in unusual cold), and closer to home, an intense windstorm or ice storm can still bring down lines and cause regional outages. The lessons of the Spain-Portugal blackout are highly relevant to Canada’s own electricity transition, because our grids are evolving and facing new stresses too.

Canada has set ambitious climate goals – aiming for a net-zero emission electricity system by 2050 (and initially even considered 2035). This means phasing out remaining coal plants, greatly reducing natural gas use, and integrating much more renewable generation like wind, solar, and storage. Several provinces, such as Alberta and Saskatchewan, currently rely heavily on fossil fuel power and are now rapidly adding renewables. Others like Ontario plan to expand wind, solar, and nuclear as they electrify more of the economy. These changes bring great benefits (cleaner air, sustainable energy, and economic opportunities), but they also require careful management to avoid reliability risks. The scenario that hit Spain – a grid with high renewables, low inertia, and heavy power transfers – could conceivably occur in parts of Canada if we don’t plan ahead. For instance, Alberta experienced a close call in 2023 when a summer heat wave drove up demand while wind generation dropped off; the province had to issue a grid alert and tap emergency reserves to avoid outages. (Notably, Alberta’s government even imposed a temporary moratorium on new wind and solar projects, partly out of concern that the pace of growth was outstripping grid integration capabilities.) Similarly, as provinces become more interdependent – say, the proposed Atlantic Loop transmission project linking Atlantic Canada to Quebec’s hydropower – a failure in one part could affect others if not backed up. Weak links in transmission or undersupply during extreme conditions are key vulnerabilities that could lead to a Spain-like situation. If, for example, a province came to rely on a single tie-line for crucial imports of power, a sudden disconnection of that line (due to a fault or maintenance error) at a time of supply stress could cause a cascading outage.

The good news is that Canadian authorities are aware of these challenges and are taking steps to address them. In fact, the federal government recently adjusted its clean electricity regulations to build in more flexibility for grid reliability, recognizing concerns raised by grid operators. Canada had initially targeted a 2035 deadline for a net-zero grid, but in late 2024 it extended the goal to 2040–2050 after feedback that the earlier timeline might risk electricity shortfalls and rising costs if pursued too rigidly. “We have learned through consultation that there was a need for some more flexibility,” Natural Resources Minister Jonathan Wilkinson said, referring to reliability and regional differences. The updated plan still cuts emissions deeply but allows provinces a bit more time to build the necessary infrastructure. Likewise, reliability is enshrined as a core principle alongside affordability and emissions reduction in Canada’s clean electricity strategy. All provinces and the federal grid regulators know that public confidence in the energy transition will evaporate if people experience rolling blackouts.

Strengthening Grid Resilience for a Net-Zero Canada

So what can Canada do – and is doing – to ensure the lights stay on through its climate-friendly electricity overhaul? Experts point to several practical steps for strengthening grid resilience amid the shift to net-zero:

Invest in Grid Infrastructure and Interconnections: Canada’s vast geography means power often must travel long distances. Upgrading aging transmission lines and building new interties between provinces can provide multiple pathways for electricity flow, so that no region is solely reliant on a single supply route. Strong interconnections allow areas with surplus power to instantly help regions with a deficit, acting as a safety valve (as France was able to assist Spain once the Iberian grid was ready to accept power). However, planners must also design these links with robust safeguards to prevent failures from propagating uncontrollably. A more meshed and modern grid, with smart sensors and automated controls, can better isolate faults and reroute power when needed.
Enhance Frequency Control and Backup Systems: As Canada adds large amounts of wind and solar, grid operators will need new tools to maintain the delicate balance of supply and demand at every second. This includes installing devices like synchronous condensers or flywheels that provide rotational inertia and voltage support to the grid (making up for the loss of big spinning turbines). It also means utilizing advanced inverters and control software so renewable plants can help stabilize frequency, not hinder it. Energy storage will play a pivotal role too – big battery banks and pumped hydro storage can absorb surplus energy and release it during sudden shortfalls, acting as shock absorbers for the system. Ensuring every region has sufficient fast-ramping backup generation (for example, quick-start gas turbines or hydropower dams) is another key reliability measure, at least until energy storage and demand-response can fully cover those needs.
Plan for Extreme Weather and Climate Impacts: With climate change, Canada is likely to face more frequent extreme weather events – heat waves, ice storms, wildfires – that can strain or damage the grid. Hardening the infrastructure is crucial. This could involve upgrading transmission towers and poles, burying critical lines underground in some cases, improving insulation and cooling systems for equipment, and creating redundancy in the network so that single points of failure (a transformer station, for example) don’t take down wide areas. Enhanced forecasting and preparation can mitigate weather-related disruptions: if grid operators know a big storm or cold snap is coming, they can pre-position repair crews, initiate controlled load reductions, or fire up reserve generators preemptively.
Cybersecurity and Grid Management: While the Iberian blackout does not appear to have been caused by a cyber-attack, the risk of one is ever-present. Canadian utilities must continue to shore up their digital defenses for the grid’s control systems. This includes rigorous security protocols, real-time monitoring for anomalies, and coordination with government cyber agencies to fend off hacking attempts. At the same time, investing in human expertise and modern monitoring systems (like wide-area measurement of frequency and AI-driven grid analytics) can help operators detect and respond to grid problems faster. Ongoing training and emergency drills will ensure that if a situation begins to cascade, operators can act swiftly to prevent a blackout or restore power promptly.

Ultimately, the blackout in Spain and Portugal serves as a cautionary tale – not that the energy transition is unwelcome, but that it must be accompanied by equal attention to reliability and grid robustness. Canada is in a strong position, with ample hydroelectric resources (which inherently provide stability), a skilled workforce, and time to learn from others’ experiences. As Dr. Bell advised, power system engineers worldwide make it a point to **“learn lessons when [major blackouts] happen, sharing those lessons internationally once investigations are completed”. The Iberian incident will no doubt yield insights that Canada’s grid planners can incorporate into their models and guidelines. By proactively addressing the potential weak links – whether technical, environmental, or human – Canada can pursue its net-zero electricity vision while keeping the lights on. In doing so, it will ensure that a cleaner energy future is also a safer and more reliable one for everyone.

Sources:

Reuters news report on the Iberian outage; Reuters explainer on causes; The Guardian coverage and analysis; The Independent analysis and expert commentary; Official statements from grid operators REE and REN via media reports; Reuters report on Canada’s adjusted net-zero electricity target; and other cited sources throughout the article.