Spain's ambitious shift toward renewable energy has been challenged by a country-wide blackout on April 28, 2025, which exposed vulnerabilities in the nation's grid stability. This incident has intensified debates over the planned nuclear phase-out by 2035, highlighting the need for a balanced approach that ensures both decarbonization and reliable power supply.

Analysis

Spain

Manager, Renewables and Decarbonization

Gabriel Ferrera Rojano

Batteries

Power 

In recent years, Spain's electricity mix has shifted significantly toward renewables. In 2024, renewable sources generated a record 59% of Spain&rsquo;s electricity, up from approximately 53% in 2023. Total renewable generation reached 146 TWh in 2024, a 10% increase over the previous year.&nbsp;
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Spain’s Grid Stability Challenge After the April 2025 Blackout

Spain is rapidly advancing its clean energy transition, marked by record growth in renewable power and an updated National Energy and Climate Plan (NECP) setting ambitious 2030 targets. However, a nationwide blackout on April 28, 2025&mdash;an unprecedented failure of the Iberian grid&mdash;has raised urgent questions about electricity system stability. The incident has intensified debates over Spain&rsquo;s planned nuclear power phase-out and the measures needed to secure reliable supply amid a renewables boom.
In recent years, Spain's electricity mix has shifted significantly toward renewables. In 2024, renewable sources generated a record 59% of Spain&rsquo;s electricity, up from approximately 53% in 2023. Total renewable generation reached 146 TWh in 2024, a 10% increase over the previous year. This growth was primarily driven by a 35.5% increase in hydroelectric production and an 18.9% rise in solar photovoltaic output, attributed to favorable weather conditions and expanded capacity&mdash;renewables now constitute 66% of installed generation capacity. Conversely, non-renewable energy sources reduced their share to 41% in 2024, down from 47% in 2023.
Wind energy led the power sources in 2024, generating 60 TWh and contributing 24% to the electricity mix. Solar photovoltaic climbed to third place with 18%, surpassing combined-cycle gas plants (CCGTs) (12%) and trailing only nuclear, which produced 52 TWh and accounted for 21% of total generation. Hydropower generated 14% (35 TWh) of the total share, varying with season and rainfall. Smaller contributors include solar thermal at 2%, cogeneration at 7%&mdash;mostly gas&mdash;and other renewable wastes, while coal output dwindled to only 1%, down from about 20% in 2015. Overall, nearly 80% of 2024 generation was emission-free (i.e., renewables plus nuclear), up from just 59% in 2015. This rapid green expansion, allowed Spain to become a net electricity exporter for the third consecutive year.
[shoojuview id="mqgmnqyeunmungagssxn"]
Source: Stratas Advisors
To build on this progress, Spain updated its NECP with more aggressive targets. Key objectives include:
<ul>
<li>Achieving 81% renewable electricity generation by 2030, up from 59% in 2024</li>
<li>Expanding solar photovoltaic and wind capacities to 76 GW and 65 GW by 2030, respectively, from 34 GW and 32 GW in 2024.</li>
<li>Increasing energy storage capacity to 22.5 GW by 2030, a significant rise from the 3.3 GW installed in 2024.</li>
<li>Enhancing cross-border interconnections to 15% of total generation capacity by 2030, up from 6% import capacity in 2024.</li>
<li>Gradually decommissioning Spain&rsquo;s seven nuclear reactors (7.2 GW) between 2027 and 2035, in line with the national phase-out plan.</li>
</ul>
Spain&rsquo;s renewable rollout is on track to meet these goals. The record 59% of renewable electricity generation in 2024 was described as &ldquo;a giant step toward the 81% target by 2030&rdquo; by the grid operator&rsquo;s chair. Renewables growth also led to a 16% reduction in electricity sector CO₂ emissions in 2024, from 32.4 million tCO₂ eq in 2023, while lowering power prices to an average of 76 EUR/MWh, down 24% year-over-year. However, the widespread blackout in April 2025, which affected Spain, Portugal, and parts of France, underscored the challenges of integrating high levels of variable renewable energy. The outage, initiated by sudden generation disconnections in southwestern Spain, highlighted issues such as low grid inertia and the necessity for enhanced balancing capacity.
This incident has reignited debates over Spain's plan to phase out nuclear power by 2035. While nuclear advocates argue for its role in providing stable baseload power, the government maintains its commitment to a renewable-centric energy transition, emphasizing that nuclear plants did not aid in restoring power during the blackout.

The April 28, 2025 Blackout&mdash;Scope and Potential Causes
On Monday, April 28, 2025, at approximately 12:33 CEST, a sudden system collapse disrupted power supply across most of mainland Spain, Portugal, and some parts of southern France. Millions of people lost power in homes, businesses, metros, and airports. Traffic and communications were disrupted, and authorities declared a national emergency, with critical services running on backup during the outage. Power began returning gradually on Monday evening, and by the next day, most areas were back online.
The exact technical causes are still under investigation. Preliminary reports indicate that the blackout began with two abrupt generation trips in southwestern Spain, just five seconds apart, which removed roughly 2.2 GW of supply&mdash;about 8% of the total demand&mdash;from the system. Spain&rsquo;s grid operator, Red El&eacute;ctrica (REE), stated that this triggered domino effects, with a break in the Spain-France interconnection shutting down the Iberian system and disconnecting it from the rest of Europe, causing a total collapse. France&rsquo;s transmission system operator, RTE, reported brief outages in parts of southern France as it fed power to Spain to aid recovery.
Hypotheses for the initiating event include a large oscillation or voltage disturbance in the Spanish grid. No evidence of a cyberattack or sabotage has emerged, with experts focusing on technical causes. Energy analysts note that the outage occurred during a period of exceptionally high renewable output&mdash;low demand and high solar generation&mdash;when much of the remaining conventional generation had been economically throttled back. At the outage moment, only about 13.6 GW of synchronous dispatchable power&mdash;approximately 3.4 GW from nuclear (out of 7.2 GW installed capacity), 3.1 GW from hydro (out of 17 GW), and 1.6 GW from natural gas (from 26.3 GW) &mdash;was online, meaning that little firm power was available to absorb oscillations. After the collapse, several solar plants and other power generation units automatically tripped offline to protect their systems amidst frequency swings, which rapidly cascaded through the system. As a result, the combination of a sudden large imbalance and reduced synchronous rotational inertia meant the grid could not stay connected.
[shoojuview id="iadfnkgqndwyiijtvsft"]
Source: Stratas Advisors


Nuclear Phase-Out Under Scrutiny
In 2019, Spain&rsquo;s government and nuclear operators agreed on a roadmap to gradually decommission the country&rsquo;s entire 7.2 GW nuclear fleet&mdash;comprising seven reactors&mdash;between 2027 and 2035. This plan, formally ratified under <a href="https://www.boe.es/diario_boe/txt.php?id=BOE-A-2024-440">Resolution 28 of December 2023</a>, was adopted in the context of growing price competition that has made nuclear generation economically unviable without subsidies. Market electricity prices have often dropped below 30 EUR/MWh, well under the estimated nuclear production cost of around 65 EUR/MWh. Operators contend that high fiscal burdens&mdash;particularly contributions to a fund for dismantling and radioactive waste management&mdash;inflate these costs by roughly 20 EUR/MWh.
However, the recent unexpected outage has prompted renewed analysis of the viability of prolonging the operation of certain nuclear reactors. This event highlights ongoing concerns regarding grid stability in power systems increasingly dominated by renewable energy sources. Specifically, the reduction of synchronous generation capacity from coal and nuclear plants has led to diminished grid inertia and weakened fault ride-through capabilities. Unlike conventional power sources, renewable generation assets such as solar panels and wind turbines connect to the grid through inverter-based systems, which lack inherent rotational inertia. Consequently, these renewable sources are limited in their ability to stabilize frequency fluctuations and mitigate potential grid disruptions arising from significant load imbalances.
Prime Minister Pedro S&aacute;nchez, of the Partido Socialista Obrero Espa&ntilde;ol (PSOE), rejected any direct link between the April blackout and Spain&rsquo;s planned nuclear phase-out. However, Ecological Transition Minister Sara Aagesen stated that the government remains open to considering extensions of reactor operations&mdash;provided formal requests are submitted by operators. Addressing Parliament on May 7, S&aacute;nchez emphasized that any proposal to extend reactor lifespans must clearly demonstrate safety, economic viability without tax relief, and a justified need for security of supply. Meanwhile, opposition parties, led by the Partido Popular (PP), have strongly advocated for a ten-year extension of all nuclear reactors, citing energy security risks and rising gas import costs in the absence of domestic gas production. This position gained traction in April 2025, when the PP secured a non-binding parliamentary resolution in support of continued nuclear operations.
Gas advocates have underscored the critical role that CCGTs played in the recovery from the April 2025 blackout, highlighting that gas-fired plants supplied up to 48% of electricity during the system restart. CCGTs are valued for their operational flexibility, capable of rapidly adjusting output to manage fluctuations in wind and solar generation. When dispatched, they contribute to grid stability by providing inertia and frequency regulation, while their fast start-up times make them particularly effective for meeting peak demand and serving as reserve capacity. According to Sedigas, Spain&rsquo;s gas industry association, the existing 26.3 GW of installed gas-fired capacity&mdash;despite operating at an average utilization rate of just 17%&mdash;could supply up to 81% of total electricity demand in a scenario where nuclear generation is entirely phased out. Meanwhile, Spain&rsquo;s aging nuclear fleet faces mounting maintenance costs, regulatory uncertainty, and persistent public concerns over radioactive waste and safety, making lifetime extensions politically contentious and economically difficult.
Nonetheless, nuclear advocates argue that gas turbines are not a full substitute for nuclear in terms of grid reliability and decarbonization. Nuclear plants provide a steady, low-carbon source of baseload electricity and essential synchronous inertia, all at a relatively low marginal cost. In contrast, although CCGTs offer dispatchability, they emit substantial amounts of CO₂, creating tension with Spain&rsquo;s climate targets. Moreover, their reliance on imported natural gas&mdash;delivered via pipelines from Algeria and through Spain&rsquo;s liquefied natural gas (LNG) terminals&mdash;raises important energy security concerns.
Despite operating the European Union&rsquo;s largest LNG regasification infrastructure&mdash;with a processing capacity of approximately 67 billion cubic meters (bcm) annually&mdash;Spain&rsquo;s gas imports remains heavily concentrated. In 2024, Algeria supplied nearly 39% of total gas imports, primarily via pipeline, while Russia and the US accounted for 21% and 17%, respectively. Despite ongoing geopolitical tensions, Spain has been unable to meaningfully reduce its dependence on Russian gas; in fact, imports from Russia nearly doubled between 2022 and 2024. This growing exposure underscores structural vulnerabilities in Spain&rsquo;s energy system and highlights the risks associated with limited diversification of natural gas suppliers.
A critical policy challenge for Spain is determining whether its existing gas and hydroelectric capacities can reliably meet peak electricity demand in the absence of nuclear power. To address this, Spain has set ambitious targets: expanding energy storage capacity to 22.5 GW by 2030 from the current 3.3 GW, and enhancing cross-border interconnections from approximately 6% to 15% of total installed generation capacity. However, achieving these goals requires significant investment and time, posing a substantial hurdle to overcome within such a short timeframe.
Spain&rsquo;s experience suggests that the significant CCGTs (26.2 GW) and hydro (17.1 GW) installed capacity will be useful but likely insufficient solution for a stable renewable-based grid. Gas turbines and hydro can replace much of the stabilizing role of nuclear in the short-to-medium term by providing synchronous inertia and on-demand power therefore help maintain frequency control as nuclear units retire. However, leaning on gas over nuclear to underwrite the renewable transition comes at the cost of higher emissions and potential vulnerability to gas supply disruptions.

Conclusion
Spain&rsquo;s energy transition stands at a pivotal crossroads accelerating renewable deployment while ensuring grid stability. The April 2025 blackout exposed systemic vulnerabilities, highlighting the imperative to embed resilience into policy frameworks. CCGTs offer operational flexibility and inertia but fall short of providing a holistic solution. Extending nuclear operations could maintain a stable, low-emission power source, but involves political, regulatory, and financial complexities. Over-reliance on gas poses risks of increased emissions and heightened import dependency. As political divisions deepen&mdash;with the PSOE upholding the 2035 nuclear phase-out and the PP alongside industry stakeholders advocating for its reassessment&mdash;the trajectory forward must harmonize decarbonization ambitions with system reliability. Ultimately, a coordinated strategy encompassing policy reforms, expansion of energy storage, enhancement of cross-border interconnections, and a potential reevaluation of nuclear timelines will be essential to fortify Spain&rsquo;s grid through its green transition.

In recent years, Spain's electricity mix has shifted significantly toward renewables. In 2024, renewable sources generated a record 59% of Spain&rsquo;s electricity, up from approximately 53% in 2023. Total renewable generation reached 146 TWh in 2024, a 10% increase over the previous year. This growth was primarily driven by a 35.5% increase in hydroelectric production and an 18.9% rise in solar photovoltaic output, attributed to favorable weather conditions and expanded capacity&mdash;renewables now constitute 66% of installed generation capacity. Conversely, non-renewable energy sources reduced their share to 41% in 2024, down from 47% in 2023.
The record 59% of renewable electricity generation in 2024 was described as &ldquo;a giant step toward the 81% target by 2030&rdquo; by the grid operator&rsquo;s chair. However, the widespread blackout in April 2025, which affected Spain, Portugal, and parts of France, underscored the challenges of integrating high levels of variable renewable energy. The outage, initiated by sudden generation disconnections in southwestern Spain, highlighted ...
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