AleaSoft Energy Forecasting, April 25, 2025. During the Easter of 2025, Spain reached a historic energy milestone: the electricity system operated with only two active nuclear reactors. With high renewable energy production, solar, wind and hydroelectric energy production, and low demand, the country not only covered its consumption, but also exported electricity. This situation marks a turning point in the energy transition and highlights the key role of storage in the future of the electricity system.
For the first time in history, the Spanish electricity system survived with only two nuclear reactors in operation. The Easter of 2025 was unusual not only because of the good weather, but also because it marked a turning point in the Spanish energy model. For several days, the country operated practically without nuclear energy: only two of the seven reactors were active, and the electricity system not only endured, but had energy left over.
What exactly happened?
For the first time since the nuclear fleet was fully deployed in Spain, the electricity mix was sustained with only two active reactors: Ascó II and Vandellós II, both located in Catalonia and managed by Endesa. The rest of the reactors remained shut down, mostly for economic reasons, in the face of extremely low wholesale electricity market prices.
Until now, average hourly nuclear energy production has never fallen below 3000 MWh. The previous minimum, registered on November 3, 2023, was 3278.8 MWh. This Easter, this historical record was broken for three consecutive days, reaching an average daily minimum of 2036.7 MWh.
Source: Prepared by AleaSoft Energy Forecasting using data from Red Eléctrica.
Renewable energy in a state of grace
A spring generous in sun and wind allowed renewable technologies such as solar photovoltaic, wind and hydroelectric energy to cover practically all demand. As a result, prices in the pool, the wholesale electricity market, plummeted, even reaching negative prices in some hours. These low prices led several nuclear reactors to shut down due to the lack of profitability of the electricity production. The low market prices also led to record electricity exports to countries interconnected to the peninsular electricity system.
Above all, however, it should be noted that the electricity system demonstrated remarkable technical resilience.
Source: Prepared by AleaSoft Energy Forecasting using data from Red Eléctrica.
Source: Prepared by AleaSoft Energy Forecasting using data from OMIE.
What does this tell us?
Events such as those that occurred this Easter, reminiscent of a similar situation registered at Easter 2024, show that the energy transition is already the present. We have gone from needing every MW of baseload nuclear energy production to sustain the electricity system, to dispensing with them without operational consequences.
It has also become clear that energy storage is and will be key. When there is excess clean energy, it needs to be stored. Batteries, pumped hydro and green hydrogen are no longer optional, they are an indispensable part of the system. All possible support must be given to ensure that storage is developed to its full potential as quickly as possible.
Reflection
Easter 2025 has been the clearest proof that the energy transition is not an abstract concept, but a real, palpable and urgent transformation. We have moved from nuclear dependence to renewable flexibility in a short period of time. Spain’s energy future is already underway, and every decision taken today will determine whether it is fully exploited.
Market balance and renewable future
The market balance is not only between supply and demand, it is also a balance in which more efficient technologies replace others that are more expensive in terms of investment and operation & maintenance. This occurred when fuel oil disappeared, then coal with the emergence of combined cycle gas turbines, and how these are being replaced by wind and photovoltaic energy. Now it is the turn of nuclear power plants, which, with their planned closures, will give way to more renewable energy, which is cheap and clean. However, these renewable technologies, as AleaSoft has been suggesting in different forums, must be accompanied by more storage, of all kinds, to make them manageable. What is the technology of the future that will end up being imposed? You can check it out at AleaSoft.
AleaSoft Energy Forecasting’s analysis on the prospects for energy storage in Europe
The AleaStorage division of AleaSoft Energy Forecasting provides forecasting reports for the optimisation and management of energy storage systems. AleaStorage services include the revenue and profitability calculation for energy storage systems, as well as the optimal battery sizing for hybrid systems with renewable energy. These services are available for stand‑alone battery projects, hybrid systems of renewable technologies, such as wind or solar photovoltaic energy, with batteries, hybrid self‑consumption systems with batteries and other hybrid systems, such as hydraulics, reversible pumping and cogeneration.
Source: AleaSoft Energy Forecasting.
