Just six months ago, Spain was left in the dark. The “electric zero” of April 28, 2025 was the most serious warning of a system that he believed himself invulnerable. Since then, Red Eléctrica (REE) operates in “reinforced mode”with dozens of gas plants turned on every day to prevent tension from skyrocketing. But, half a year later, the problem is still there: the Spanish grid is faltering not because of a lack of energy, but because the gas is in the north and the sun is in the south.
How are the measurements now? At the beginning of October, the National Markets and Competition Commission (CNMC) approved, at the request of REE, an emergency resolution to introduce exceptional measures “in the event of sudden voltage variations” detected in the system. The document details changes to several operating procedures that affect the way the electrical grid is programmed and regulated. In practice, the rules of the game were tightened for everyone: from solar producers to gas plants.
Among the most significant measures is the obligation for renewable plants to carry out their power transitions in a minimum of 15 minutes, when before they did so in two. The intention, have explained from REEis to avoid sudden changes that could destabilize the system and give the thermal power plants time to react. As explained in Cinco Díasthis instruction allows gas plants to “absorb” excess renewable energy without causing power surges. But for many expertsthe underlying diagnosis is different: the problem is not speed, but geography.
Two electric Spains. The country is experiencing a geographic imbalance that we already saw it coming. On the one hand, the north and the Mediterranean coast concentrate the majority of thermal power plants and combined cycle plants – the only ones capable of providing the so-called “rotating mass”, that is, inertia and reactive power that stabilize the network. On the other hand, the south of the peninsula—Andalusia, Extremadura and Castilla-La Mancha—has been filled with solar plants and domestic self-consumption, technologies based on power electronics that do not generate natural inertia.
“During peak radiation hours, the south produces more electricity than it consumes, the lines are discharged and the grid becomes extremely sensitive,” explains in his column Joaquín Coronado, president of Build to Zero. Under these conditions, starting a thermal power plant in Asturias to stabilize a voltage problem in Seville is as useless as trying to put out a fire in Andalusia with water pumped from Galicia.
The tension starts from the local. The error of approach is in confusing frequency with tension. The electrical frequency is a global magnitude: it is the same throughout the synchronous network. But the voltage is a local variable, which depends on the reactive power flows in each area. Coronado sums it up clearly: reactive power “does not travel well.”
- On 400 kV lines, its radius of action is 30 to 80 km.
- In 220 kV networks, from 15 to 40 km.
- And at 132 kV or lower, just 5 to 20 km.
This means that a turbine in the north cannot stabilize the voltage in the south, no matter how much power it has. The CNMC, in its resolutionrecognizes precisely that “rapid voltage variations” appear in periods of low demand and high solar production, aggravated by the growth of self-consumption that “reduces the observability of the system” and leaves the operator without control over thousands of small installations. In summary and how we have explained in Xataka: we have more sun than cables.
This shows in the pocket. REE’s response has been to maintain lit every day between 20 and 30 combined cycles to ensure stability. This “reinforced operation” has cost more than 1 billion additional euros since April and could add 3 billion more with the new measures. Adjustment services – energy that is paid outside the daily market to keep the network stable – have gone from 240 million in 2019 to 4 billion in 2025, according to Cinco Días.
The result is paradoxical: Spain has one of the lowest wholesale prices in Europe, but one of the highest electricity bills. Ember’s report explains why: the market price only covers half of the bill; The other half are fixed network costs, tolls, taxes and system stability, which do not go down even if energy is cheap.
Slowing down is not stabilizing. The decisions adopted by REE and temporarily endorsed by the CNMC are “a defensive strategy” for Coronado. Furthermore, he points out that instead of providing the system with rapid response capacity, it is chosen to slow it down to give time to the thermals. The result is maintaining “a 21st century system operated with a 20th century mentality.”
Slowing down the renewable ramps does not provide voltage control where it is needed, because the problem occurs in seconds and in specific places, not in the 15 minutes that these ramps last. The measures, therefore, gain time, but they do not gain effectiveness: they mitigate the frequency, not the tension.
Is there any future perspective? The solution is to bring the control capacity closer to where the energy is produced. In fact, we have already discussed in Xataka some of those possible solutions that agree with what Joaquín Coronado says.
- Grid-forming inverters in solar and wind plants, able to behave as synchronous generators and stabilize the network in milliseconds.
- Batteries strategically distributed in the southern nodes, which provide instantaneous active and reactive power.
- Devices FACTS and synchronous compensators in critical substations (Guillena, Mérida, Puertollano…) to dampen local voltage changes.
- Flexible demand from large industries to modulate consumption in real time.
- And predictive algorithms based on artificial intelligence that anticipate local instabilities.
Some of these solutions are already underway. Spain prepare the installation of eight synchronous compensators and 2,600 MW of batteries, with 340 MW already approved. These devices could save 200 million euros annually by reducing the use of gas for network services.
A model that is exhausted. Beyond the technique, there is a structural dilemma: how long can a transition that depends on gas to stabilize renewables be sustained? The CNMC admits that the current measures They are “temporary and exceptional” and that must be reviewed in an extendable month. But the operator itself recognizes that the system “lacks observability and rapid response” in the south.
Meanwhile, political pressure is growing. Photovoltaic associations warn that these limitations reduce the entry of renewables and the income of the sector. And some experts —cited by Cinco Días— they speak of “a posthumous victory for conventional plants,” which thus see their support function legitimized.
A network between two times. Half a year later, here we are, Spain trapped between two models: one that needs mechanical inertia and another that requires digital intelligence. The electrical grid has become the mirror of a half-finished transition due to speed.
“A solar plant with grid-forming in Andalusia is worth more for local stability than ten combined cycles in the north,” wrote Joaquín Coronado. The phrase summarizes the Spanish paradox: we have the generation of the future, but we continue to use the crutches of the past. Because 21st century electricity is not measured in megawatts, but in milliseconds. And the stability of the system no longer depends on the gas burning in the north, but on how quickly – and intelligently – the southern sun is managed.
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