The impact of nuclear shutdowns in Spain

Nuclear energy has become a key pillar of global energy policy due to its ability to deliver reliable electricity and stabilise power grids at a competitive, carbon-free cost. While countries such as France, the United States, China, and the United Kingdom are moving to extend the operational life of their nuclear reactors—or even build new ones—Spain is swimming against the tide. This country has adhered to a phased closure plan for its seven operating reactors, set to begin in 2027 and conclude by 2035.

This plan originated in 2019 from a ‘closure protocol’ agreed upon by nuclear operators and the state-owned company ENRESA. The driving factor behind the decision was the sharp increase in taxes and levies, which significantly worsened the plants’ financial viability. Specifically, nuclear taxes and levies rose by 90% from 2010 to 2019 (the year the protocol was signed), followed by another 70% hike by 2025. As a result, Spain’s nuclear plants face a serious risk of becoming economically unsustainable despite their cost-efficient operations, as total operating costs now exceed projected electricity market prices.

Spain currently operates seven nuclear reactors with a combined installed capacity of 7,117 MW. Due to their characteristics, nuclear plants are a critical pillar of Spain’s energy system:

• They provide system stability with extremely high availability. Nuclear units can run at full load nearly all year long, except during planned outages for refuelling or maintenance (typically 30 days every 12–18 months). Nuclear is the baseload of Spain’s electricity generation, supplying around 20% of total electricity demand annually.
• As a synchronous technology, nuclear adds resilience to the grid, supporting security during potential grid disturbances or failures in other generation sources. Like hydroelectric and combined cycle plants, nuclear plants convert mechanical energy from turbine rotation into alternating current electricity. This is essential for grid frequency and voltage control, given that higher generation from these technologies reduces grid disturbances caused by punctual imbalances between supply and demand. This technical role became a topic of major debate after the 28 April total blackout on the Spanish peninsula, where early information and assumptions pointed to the availability of synchronous generation as a key factor in the incident. 
• Furthermore, nuclear energy can be considered domestically sourced from a practical standpoint, thanks to the uranium availability, the wide range of suppliers, and the storage capacity. Therefore, it shields the electricity system from fossil fuel market volatility, notably impacted by the geopolitical context.

According to Spain’s National Integrated Energy and Climate Plan (ENCP), four of the country’s seven reactors will be shut down by 2030. The plan also lays out ambitious goals for the development of renewables, especially solar PV and wind. While these goals may be technically achievable—given Spain’s recent progress in deploying solar PV—success at such scale requires simultaneous investment in both grid infrastructure and energy storage. Without that, it will not be possible to safely and reliably integrate the renewables.

This poses a significant challenge, as existing administrative, economic, and environmental barriers continue to hinder both grid and storage expansion. As for energy storage, the NECP envisions 22.5 GW by 2030 through a mix of battery systems and pumped hydro. Currently, only around 3 GW of pumped storage is in operation. The combination of these obstacles—alongside the lack of a regulatory framework that ensures economic viability for these technologies—has slowed their deployment. Consequently, this situation makes it difficult to meet the NECP’s objectives and, therefore, to complement the growth of renewables.

It is also important to note that the Iberian Peninsula is an energy island, with only 2% interconnection capacity compared to its installed generation capacity. This is far below the EU’s targets of 10% by 2025 and 15% by 2030. While additional interconnections with France are planned, Spain’s geographic limitations mean it will still fall short of recommended exchange capacity levels. As a result, these geographic limitations restrict the integration and resilience of Spain’s peninsular electricity system within the broader European electricity system.

In this context, phasing out nuclear generation would expose the national grid to supply risks. Therefore, it will likely require increased generation from combined cycle plants, which are needed to replace the stability lost from nuclear. This would lead to raised emissions in the electricity mix and higher electricity market prices—as combined cycle plants have significantly higher operating costs and are dependent on natural gas and CO₂ prices.

Projections suggest that keeping nuclear plants in operation could reduce the average electricity market price by €13/MWh under normal market conditions and by up to €30/MWh under less favourable conditions. Nuclear closures would also have a serious socioeconomic impact, given the sector’s role in employment and GDP, especially in regions that host reactors. The industrial and business fabric in these areas would be heavily affected. Without nuclear, industrial competitiveness and economic growth are at risk, especially as Spain tries to meet rising demand using more expensive and less sustainable energy sources.

Considering these consequences, a period of re-evaluation should begin regarding the suitability of adhering to the current closure schedule—a debate involving the government, political groups, and society at large, which will ultimately bear the brunt of the decision. However, extending the operation of nuclear plants won’t be feasible under the current tax burden they face. Therefore, a dialogue between authorities and operators is urgently needed to find a viable solution for all stakeholders. It is worth emphasising that nuclear energy is currently the only technology capable of supplying stable, continuous, and CO_₂-free electricity while also providing frequency stability to the grid.

Summarising, Spain faces a major challenge in phasing out its nuclear fleet—an agreement made in a very different geopolitical and energy context. The consequences could be severe, both economically and in terms of energy security. There is still time to find a solution that allows for continued nuclear operation, but time is running out. Once the Almaraz plant shuts down in 2027, the closure of the remaining plants will likely be irreversible.