Spain’s nuclear power sector is approaching a decision that will shape the national electricity system for more than a decade. The country still officially plans to close all seven operating reactors between 2027 and 2035. However, plant owners are seeking longer operating periods, beginning with the two reactors at Almaraz.
The debate is not mainly about constructing a new Spanish nuclear fleet. No large reactor project is under development. The immediate question is whether existing plants should close according to the schedule agreed in 2019 or continue operating while Spain adds renewable generation, storage, transmission capacity, and other sources of system flexibility.
That question has become more significant because nuclear power remains one of Spain’s largest individual sources of electricity. In 2025, the seven reactors produced approximately 19% of national generation, placing nuclear behind wind but close to solar photovoltaic and ahead of several fossil-fuel technologies.
Seven Reactors Still Anchor Low-Carbon Generation
Spain operates seven reactors at five nuclear power plants. Almaraz in Extremadura and Ascó in Catalonia each have two units. Cofrentes is located in the Valencian Community, Vandellós II in Catalonia, and Trillo in Castilla-La Mancha.
Most of the reactors are pressurized water units. Cofrentes is Spain’s only operating boiling water reactor, while Trillo is based on a German pressurized water design. The fleet was connected to the grid mainly during the 1980s, making long-term operation, equipment replacement, inspection, and periodic safety reviews central to the industry’s current work.
Spain’s nuclear plants provide steady electricity with low direct carbon emissions. Their role differs from that of the country’s rapidly expanding wind and solar fleet. Solar output follows daylight and weather conditions, while wind generation can change significantly across hours and seasons. Nuclear plants generally operate for long periods at stable output, apart from refueling and maintenance outages.
This does not mean that nuclear generation and renewables cannot coexist. Spain already operates both at substantial scale. In 2025, renewable technologies supplied 55.5% of national electricity generation, while nuclear supplied another 19%. Together with other low-carbon sources, they helped Spain produce more than three-quarters of its electricity without direct carbon-dioxide-equivalent emissions.
The policy issue is therefore not a simple choice between nuclear and renewables. It concerns the timing of reactor closures and whether replacement capacity, storage, network reinforcement, interconnection, and flexible demand will be available when the plants leave the system.
Almaraz Has Become the Test Case for the Entire Fleet
The existing schedule begins with Almaraz unit 1 in November 2027 and Almaraz unit 2 in October 2028. Ascó I and Cofrentes are scheduled to follow in 2030, Ascó II in 2032, and Vandellós II and Trillo in 2035.
This creates an important concentration of closures at the beginning of the program. Four reactors representing several gigawatts of firm generating capacity are scheduled to leave service by the end of 2030. The remaining three would then close during the first half of the following decade.
In October 2025, the owners of Almaraz—principally Iberdrola, Endesa, and Naturgy—formally requested permission to keep both units operating until June 2030. The proposal would add approximately three years to the current timetable and delay the beginning of Spain’s nuclear phaseout.
As of June 2026, the government had not issued a final decision. The request requires technical review by the Nuclear Safety Council, while the government must also consider electricity security, costs, and consistency with national energy policy. A decision was expected later in 2026.
Almaraz is more than an isolated licensing case. Approval would establish a path that owners of other Spanish reactors could attempt to follow. Iberdrola has indicated that extensions could eventually be sought for the wider fleet, while operators of the Catalan plants have also emphasized their ability to continue beyond their scheduled dates.
A rejection would preserve the current sequence and make Almaraz the first major step in Spain’s nuclear withdrawal. It would also place greater pressure on grid investment and replacement resources before the end of the decade.
Economics May Decide More Than Reactor Age
The Spanish nuclear debate is often presented as an argument over safety or ideology, but plant economics are equally important. The reactors can operate only if their owners are willing to finance maintenance, staffing, fuel, inspections, waste management, taxes, and required upgrades.
Operators argue that Spain’s nuclear tax structure and contributions to radioactive-waste management place heavy costs on the plants. Low wholesale electricity prices during periods of strong renewable output can further reduce revenue for generators that cannot easily reduce production.
The government has stated that any extension should not create additional costs for consumers or taxpayers. This condition makes the negotiations more complex. Plant owners want an operating environment that makes continued service commercially viable, while the government does not want to subsidize assets that were already scheduled to close.
The outcome may depend on the treatment of nuclear taxes and the charge paid to Enresa, the state-owned company responsible for radioactive-waste management and decommissioning. Extending reactor operation would produce more electricity and more revenue, but it would also generate additional spent fuel and delay parts of the existing decommissioning program.
The nationwide blackout of April 28, 2025, gave the debate additional political force. The event renewed public attention on grid strength, system inertia, voltage control, interconnection, dispatchable generation, and the speed of Spain’s electricity transition. It did not prove that nuclear power alone could prevent a major grid failure, but it made policymakers and companies more cautious about removing firm generation before replacement capabilities are ready.
Spain’s Renewable Growth Changes the Nuclear Calculation
Spain has some of Europe’s strongest solar and wind resources and has expanded renewable capacity quickly. Solar photovoltaic generation reached 18.4% of national production in 2025, while wind contributed 21.6%. Including estimated self-consumption, solar’s role was even larger.
This growth supports the government’s argument that Spain can progressively replace nuclear output with renewable electricity, storage, stronger grids, demand management, and international connections. It also creates periods in which low-cost renewable generation can cover a large share of demand.
However, replacing annual nuclear production is not the same as replacing the system services available from nuclear plants at every hour. A successful phaseout requires enough low-carbon electricity during evenings, low-wind periods, winter demand peaks, droughts, and prolonged weather conditions that reduce renewable output.
Combined-cycle gas plants can provide flexible backup, but greater gas use would increase fuel imports and emissions. Batteries are expanding rapidly, yet most current systems are designed for shorter-duration balancing rather than several days of weak renewable production. Pumped hydropower, demand response, interconnectors, and future storage technologies will therefore influence how easily Spain can close its reactors.
The strongest argument for extension is not that Spain should stop building renewables. It is that existing nuclear plants could provide low-carbon electricity while the infrastructure needed for a renewable-dominated system is completed. The strongest argument for the current closure plan is that a fixed timetable gives investors, regulators, plant communities, and waste authorities a clear transition path and prevents temporary extensions from becoming an indefinite policy.
Waste and Decommissioning Continue After Generation Ends
Reactor shutdown does not end Spain’s nuclear obligations. Spent fuel must remain safely stored, plants must be dismantled, contaminated materials must be managed, and affected sites require monitoring and redevelopment planning.
Spain’s Seventh General Radioactive Waste Plan, approved in December 2023, is based on the closure of operating reactors between 2027 and 2035. It replaces the earlier emphasis on one centralized interim storage facility with a decentralized approach at nuclear sites. Each relevant location is expected to have sufficient temporary storage for spent fuel and high-level waste until a permanent geological repository becomes available.
The shift toward decentralized storage reflects the long delays and political difficulties associated with selecting one national interim-storage location. It also means that nuclear sites may continue hosting spent fuel for decades after electricity generation stops.
Enresa will oversee decommissioning and waste-management work, funded largely through charges connected to nuclear generation. Changes to reactor operating dates therefore affect staffing, contracts, waste volumes, storage construction, and the schedule for transferring plants from utilities to the decommissioning authority.
Spain’s Nuclear Future Now Depends on Timing
Spain is not choosing between an unchanged nuclear system and an unchanged renewable system. Its power sector is already transforming. The question is whether the nuclear timetable agreed in 2019 still matches the speed of electricity-demand growth, renewable integration, storage construction, network reinforcement, and energy-security concerns in the second half of the 2020s.
The decision on Almaraz will provide the first clear answer. A limited extension to 2030 could preserve the final 2035 phaseout date while changing the order and pace of closures. A broader revision could keep several reactors operating into the late 2030s or beyond. Rejection would confirm that the planned withdrawal will begin in November 2027.
Spain has enough renewable potential to build a deeply decarbonized electricity system. Whether it closes its nuclear plants on the existing schedule will depend on whether the government believes that the replacement system will be ready before the reactors are removed.
