Next Wednesday, August 12, Spain will witness an exceptional astronomical event: a total solar eclipse that will cross the Iberian Peninsula from west to east. It will be the first of its kind visible from the peninsula in over a century, since the last one occurred in 1912. This phenomenon, which will also be visible in parts of Europe, has put electricity operators on alert, as they prepare for a temporary drop in photovoltaic production.
Solar power generation will be affected during the minutes when the Moon completely obscures the Sun. However, authorities and electricity companies agree that the impact will be limited, mainly because the eclipse will take place at sunset, when photovoltaic production is already in its natural decline phase. Even so, coordination protocols have been activated at the national and European levels to guarantee the stability of the supply.
Expected reduction in photovoltaic production
Red Eléctrica de España (REE) has calculated that solar power production could fall by around 5 gigawatts (GW) during the eclipse, representing approximately 13% of the peak demand recorded on a typical Wednesday in August. This figure, while significant, does not compromise supply coverage, according to the system operator. The company has developed its own mathematical model that simulates, minute by minute, the movement of the Moon's shadow over each province and island, allowing for a precise estimation of the generation loss.
The moment of greatest darkness will occur between 20:26 PM and 20:33 PM, peninsular time, very close to sunset. This timing is key to understanding why the effect will be less than if it occurred during the middle of the day . During this period, photovoltaic production is already naturally decreasing, so the eclipse will accelerate and slightly accentuate this decline, without coinciding with the usual peak demand for August days.
However, the final impact will depend on weather conditions. If the sky is cloudy, production will already be low and the effect will be almost imperceptible ; if it is clear, the drop will be more evident. In the Balearic and Canary archipelagos, the phenomenon will not have a significant impact on photovoltaic generation, according to REE's forecasts.
Preventive measures and European coordination
In response to this situation, Red Eléctrica has announced a package of preventative measures. The company will increase the system's reserves and usual safety margins , and will maintain constant monitoring of the phenomenon. Coordination with official bodies, other European transmission system operators (TSOs), and national generation and distribution control centers will also be strengthened.
The European Commission has confirmed that the European Network of Transmission System Operators for Electricity (ENTSO-E) will hold a coordination meeting with national operators to assess the potential effects of the eclipse. The Commission's Energy spokesperson, Anna-Kaisa Itkonen, indicated that the impact will not be significant due to the timing of the phenomenon , but stressed the importance of preparation and monitoring. Brussels does not anticipate supply problems, although it will closely monitor any factors that may have an impact.
Coordination between countries is essential in an interconnected electricity system like Europe's. Interconnections will allow countries with greater generation capacity to temporarily support those most affected by the eclipse . Furthermore, compensatory mechanisms such as hydroelectric plants, combined cycle gas turbines, and investments in energy storage will be activated , allowing them to be quickly connected to the grid to cover any fluctuations.
Precedents and lessons learned
This is not the first time a solar eclipse has tested the European electricity grid. In March 2015, a partial eclipse caused a reduction of approximately 35.000 MW in the continent's photovoltaic generation , an amount equivalent to dozens of conventional power plants. On that occasion, the system withstood the challenge without major incidents, demonstrating the operators' ability to adapt.
In Spain, experience is more limited, as the last annular eclipse visible in the country was in 2005, when solar energy was still relatively uncommon. Today, photovoltaic solar energy is expanding in Spain, playing a much larger role in the electricity mix, and there are also more tools to manage its variability. According to experts, even if the eclipse were to occur at midday, the system would be prepared to handle it thanks to reserves and the rapid response of other energy sources.
Professor Tomás Gómez-Acebo, Chair of Thermodynamics and Director of the Chair of Energy Transition at Tecnun, explained that the difference in production will be equivalent to the passage of occasional clouds, practically imperceptible . These fluctuations will be offset by hydroelectric and gas-fired power plants, which can be connected to the grid in just a few minutes.
A challenge for demand management
The eclipse will also test real-time demand management. Operators will need to adjust generation forecasts and maintain sufficient buffer reserves to prevent supply and demand imbalances. The rapid recovery of solar production after the eclipse, once radiation returns to full levels, will also require a swift response to absorb the increased energy demand.
Electricity companies have noted that in August 2025, solar production in Spain reached 5.822 GWh, one of the best months of the year. This figure reflects the importance of photovoltaic solar energy, which is breaking records in the system, but also the need to plan for exceptional events such as the eclipse . The experience gained in other European countries, where similar phenomena have already been managed, will serve as a reference for minimizing any risk.
In short, the August 12 eclipse will be a visually spectacular event, but also a test of technical coordination. Authorities and electricity operators have worked for months to ensure that solar energy production is not compromised and that the electricity supply remains stable at all times. Although the 5 GW reduction is significant, the system is prepared to compensate for it with other sources and through energy swaps between countries.
With all the forecasts in place, the eclipse is expected to proceed without significant disruptions to the electrical grid. The combination of reserves, European coordination, and constant monitoring will allow us to handle this phenomenon with confidence , just as we did in 2015. Citizens can enjoy the astronomical spectacle with the peace of mind that, this time, the power will not go out in their homes.
