In just five seconds, the Iberian Peninsula suffered a sudden loss of 15 GW of generation capacity, equivalent to 60% of the country's electricity demand, leading to an unprecedented supply cut. While the exact causes of the system crash are still being investigated, the Director of Operations Services at Red Eléctrica de España, Eduardo Prieto, indicated yesterday that “two generation losses in the south-west of Spain” were among the triggers. According to Red Eléctrica Española, the issue was caused by an unexpected drop in electricity generation — in other words, a significant portion of the forecasted production failed to materialise. But how could this have brought down the entire system in just five seconds?

“These types of incidents result from the amount of power lost combined with the speed at which it happens,” explains Ramon Gallart, Director of Innovation at Estabanell. “To better understand it, we can imagine the electricity grid as a balance constantly maintained between energy production and consumption. Any sudden mismatch between the two can create problems, such as frequency fluctuations, which may lead to a blackout. In this case, part of the generation failed — the technical reasons are unknown — but there wasn’t enough immediate capacity to compensate for it,” says Gallart.

This imbalance between supply and demand triggered an automatic system disconnection as a protective measure. “If a generator disconnects unexpectedly, or if a fault in the grid could cause problems, systems automatically isolate the failing part. This helps maintain grid stability and prevents a small issue from becoming a bigger one,” Gallart explains. He adds, “this highlights the importance of having safety mechanisms and backup systems that can respond quickly to such unforeseen events.”

The Low Inertia of Renewables in Managing Imbalances

Some experts have also emphasised the importance of the concept of inertia in energy to understand what happened. “In physics, the principle of inertia — when applied to energy — refers to a system’s ability to maintain a stable supply despite demand fluctuations or other imbalances,” Gallart explains. As Vice President of the European Association of Energy Distribution Companies and Organisations, he notes that renewable energy sources, such as wind and solar, lack inertia and rely on natural conditions, which can be variable and difficult to predict, such as wind or solar radiation. This means that their supply may not be able to match demand quickly at certain times. Traditional sources, by contrast, can be regulated more easily.

Nevertheless, Gallart points out that with technological progress, particularly in energy storage (such as large-scale batteries), renewables can overcome these imbalances. Smart grid systems are also improving the ability to coordinate generation and consumption, managing the gaps between energy supply and demand more effectively.

The Redeia Report Warning of Disconnection Risks Due to Renewable Growth

In recent hours, a two-month-old report has come to light, in which the system operator, Red Eléctrica Española (Redeia), warned of the risk of severe disconnections due to the increasing share of renewables. On one hand, Redeia highlighted the rise of renewable production via small installations, which are less capable of adapting to disturbances. On the other hand, it noted the closure of conventional generation plants — coal, combined-cycle (gas), and nuclear — which reduces the system’s resilience to sudden shocks.

According to Gallart, a sector expert, “the issue isn’t that there is too much self-consumption generation, but that the centralised system often doesn’t know how much energy is actually being generated or how that pattern is changing throughout the day, which can cause sudden imbalances in the grid.” He gives a hypothetical example: if solar generation systems suddenly stop producing because clouds pass over or radiation drops in an area with a high concentration of self-consumption, the grid may be forced to activate backup generation immediately. “In such a case, if there isn’t that margin of manoeuvre, issues like voltage problems or even disconnections could occur,” he states.

For this reason, one of the lessons Gallart draws is that we must “digitise and modernise the grid, incorporate intelligent management systems, integrate storage such as batteries, and promote better communication between self-consumption facilities and the central system to ensure that the energy transition towards a cleaner and more decentralised model is carried out safely and reliably.”

Improving External Interconnections

Another key solution to ensure greater stability in Spain’s electricity system, according to experts, is the urgent improvement of electrical interconnections with France and Morocco. Currently, the interconnection capacity with France represents just 5% of Spain’s installed capacity — a figure far from the 10% recommended by the European Union for a resilient and efficient electricity market.

According to Gallart, this is a “key strategy” because “it allows for greater capacity to import electricity when needed, and to export it when we have surpluses — especially during periods of peak renewable production.” For the Director of Innovation at Estabanell, “this is a smart way to turn the variability of renewables into an opportunity, as it encourages green energy integration, avoids waste, and reduces reliance on fossil fuels.”

Doubts Cast Over Renewables

The power outage and the hypotheses under consideration as to its causes raise questions about renewables and their integration into the grid, as well as the potential risk they pose to its security. Gallart says, “It’s true that sources like solar and wind are variable and dependent on natural factors, but that doesn’t make them a problem. The real challenge lies in how this generation is integrated into the grid — and that’s where technology plays a vital role.” That’s why, he adds, the key is to continue rolling out renewables alongside the tools that ensure safe and efficient integration.

In this context, experts also stress that the development of renewable energies and the electrification of demand should not be called into question. “It’s incomprehensible that situations like this could lead to distrust among some of the public or industry. But blaming these episodes on the growth of renewables is a diagnostic error that could unfairly hinder a necessary transition,” Gallart states. What we experienced on Monday, he continues, should serve as a catalyst for identifying where the system needs reinforcement and pushing forward with greater determination toward a more modern, digital, clean, and resilient energy model. Photovoltaic technology is mature and fully meets all the requirements that the system operator has demanded at all times.