The cause of the blackout is still unknown. The system recovered in the early hours of Tuesday and is now operating normally. Today, the price of electricity will be close to 32 euros.
Why is electricity more expensive after the blackout?
There are several reasons. The first, more mundane reason is that on Tuesday, the price of the megawatt-hour (MWh) in the wholesale market was extremely low, averaging 5.79 euros, with several hours at 0 euros or even negative prices, according to OMIE data. Today's price of 31.83 euros/MWh is much higher in comparison, but still far from the peak in April at 64.39 euros, and in March, for instance, it exceeded 110 euros. Therefore, with such a low starting point, any alteration will be significant, but there will still be hours with prices at 0 or below.
Another factor is the system's own recovery, involving combined-cycle power plants. These plants usually set the price as they depend on a raw material, gas, which represents an investment that needs to be recovered. This was the reason why the electricity price surged after the Ukraine invasion - actually, even before - as the fuel price also increased. Yesterday, these plants operated despite not being planned, and today they will also operate but in a different context.
It is a somewhat complex process that somewhat stabilized after the measures introduced by the Government to prevent volatility. However, to understand the peaks, it is important to know that electricity is sold in a reverse auction. Every day, the operator calculates the expected demand for the following day, and then companies go to the market to buy those megawatts, while others sell them. But it is a reverse auction: the price is set by the latest technology to enter the pool. To simplify - considering many technologies at play - imagine that for a specific hour, there is a demand for 25,000 MW, and 11,000 MW are offered from photovoltaic sources, 8,000 MW from wind, 5,000 MW from nuclear, and 1,000 MW from hydroelectric, all selling their production at 0 euros: the price will be that. However, if instead of 1,000 MW from hydroelectric, there are 1,000 MW from combined-cycle plants selling at 117.01 euros (today's peak), then all electricity negotiated will be sold close to that price (the measures to prevent volatility would come into play, which are not considered in this example).
This system's idea is precisely to promote the development of non-polluting and cheaper sources because, with no production costs, they can offer at zero euros, knowing they will always be attractive compared to other technologies with operating costs. Polluting sources, moreover, need to recover when they have the opportunity to enter the market.
In any case, this only affects the regulated market, which includes customers with the PVPC rate (Voluntary Price for Small Consumers), who depend on the price negotiated in the wholesale market. Customers with a fixed-rate contract do not experience these daily fluctuations, although they may be subject to trends in the medium and long term.
What does gas have to do with all this?
Gas, along with hydroelectric power and assistance from France and Morocco, helped restore the system and operated at a high pace in the early hours of the day until the system recovered, especially when the sun rose, and photovoltaic power came into play.
How did France and Morocco help restore the system?
They used their border connections to transmit tension to Catalonia, the Basque Country, and Andalusia. This allowed them to activate their systems, the auxiliary services of the generation systems that had also failed, and from there, ensure it reached the rest of the peninsular electrical system. Subsequently, the network began to come to life as the process was repeated in new generation plants.
A group of hydroelectric plants from different basins (Duero, Tajo, Pyrenees, Levante...) with the ability to start autonomously also started up when the blackout was detected and proceeded to connect to the grid. Their role was, therefore, similar to that of Morocco and France: establishing areas capable of producing and gradually expanding as they reached new supply points. The tension spreads throughout the entire network until there is an interconnection of the entire system. Combined-cycle plants burn fuel - usually gas - and can be started relatively quickly, making them key in the process.
Why did the blackout occur?
The reality is that it is not known. In fact, it is not known when it will be known: Red Eléctrica prefers not to commit to a timeframe. The company has ruled out causes such as cyberattacks and atmospheric conditions. This was explained by Eduardo Prieto, director of services for the company's operation, at a press conference.
As detailed by Prieto, before the blackout, the system was "stable" in all its variables and in safe conditions. The generation mix before the incident was around 17,000 to 18,000 MW from photovoltaic sources, with significant wind and nuclear power, around 3,000 MW each. They then detected "an event in the electrical system compatible with a loss of generation" in the southwest region of the peninsula. This event disrupted frequency and voltage, but then stabilized. A second and a half later, another event "compatible with a loss of generation" occurred, affecting these variables again. This led, 3.5 seconds later, to the disconnection with France and the blackout. Everything happened in five seconds.
Red Eléctrica also stated "categorically" that there was no order to disconnect generation sources impersonating them. There was no cyberattack, no one pretended to be the entity to shut down the grid, making generation unable to respond to the electrical demand.
Hours later, during his media appearance, Prime Minister Pedro Sánchez stated that "it would be imprudent to rule out any hypothesis," including hacking. "Our second priority is to find out what happened," explained Sánchez, who pointed out that both Red Eléctrica and electricity-generating companies are analyzing the data to understand "what happened in those five seconds that led to the system's collapse." He urged the media to provide verified information: "haste should not lead us to misinformation and error." Throughout Monday, Red Eléctrica provided information on the system's recovery process, but its website displayed incorrect data in some sections because, as the company explained, some figures remained 'frozen,' showing information prior to the blackout. Although they detected this, they acknowledged that, logically, they focused their efforts on restoring the electrical system to operation.
What is the composition of the Spanish generation system?
So far this year, as in 2024 and 2023, wind power has been the main source of generation, currently contributing 24.9% of the total. Nuclear power has generated 20% of the national electricity this year, a percentage similar to its usual share (since 2007, it has never dropped below 18% and never exceeded 22.2%). The third place on this podium, for now, goes to hydroelectric power, contributing 17.2%, which has been crucial for the mix, although it is important to note that it is affected in drought years, like 2022 (ending with 6.6% of the total). Solar photovoltaic power (14.2%) will need to increase its contribution in the coming months with more sunlight hours. Combined-cycle power is more versatile, so it fluctuates according to the system's needs. In 2025, it represents 12.4%, but in 2022, it led the mix (24.7%), in 2014 it was at 9.3%, and in the years when coal-fired power plants began to disappear, it was the leading technology.
It should not have happened, although the Monday blackout should not have occurred either. But if it had an impact, it was precisely because it is not the norm. The system is theoretically robust and has redundant sources: if one fails, another takes its place. It has experienced tense moments like Storm Filomena, heatwaves causing wind production to plummet, or times when France, Morocco, and Portugal import Spanish electricity simultaneously. It also has additional safeguards, such as the ability to disconnect large consumers in case of an unexpected demand peak. However, until the cause of the blackout is known, it is impossible to predict if the same phenomenon will occur again.