By ESS news
A year after the power outage of April 28, 2025, technical analyzes and responses from regulators have reshaped the concept of security of supply in the Spanish electricity system, which has been undergoing rapid transformation since 2018 due to the high penetration of renewable energy sources. Rather than being an isolated incident, expert reports – including those from the commission appointed by the Spanish government, Red Eléctrica and ENTSO-E – conclude that the blackout resulted from a combination of operational and structural factors that exposed vulnerabilities in a system increasingly dominated by renewable technologies.
The event began with the sudden loss of approximately 15 GW of generation within seconds, triggering a cascading outage that led to a nationwide blackout. The sequence included voltage deviations, frequency instability and automatic shutdowns, highlighting the critical importance of real-time system control.
One of the main causes identified was insufficient voltage regulation capacity, coupled with the reduced presence of synchronous generation. In a system with a high proportion of non-synchronous renewable energy sources such as solar and wind, the provision of ancillary services – including inertia, frequency control and reactive power – becomes more complex, limiting the system’s ability to absorb disturbances. This was further exacerbated by the limited deployment of energy storage – around 28 MW of batteries at the time – limiting rapid response capabilities, as well as low levels of interconnection with adjacent systems, limiting external support.
The overall diagnosis points to a system failure rather than a single cause: a series of conditions and events that exceeded the system’s resilience. This insight has led to follow-up measures aimed at strengthening both operational management and long-term system planning.
Boost for storage
Although installed battery storage capacity has grown by more than 500% since the blackout, Spain still ranks lowest in Europe, far behind countries such as Germany, Italy and the United Kingdom, which have each installed several gigawatts.
According to Red Eléctrica, Spain had only 28 MW of installed battery capacity in April 2025. By April 2026, this had increased to 193 MW, representing a year-on-year growth of 589%. At the same time, the pipeline of BESS projects expanded significantly, with project processing increasing 464% year-on-year.
The demand for storage in the self-consumption segment also increased sharply. In 2025, capacity grew from 155 MWh to 339 MWh, an increase of 119%, according to APPA Renovables. Residential installations increased by 155%, while commercial and industrial installations increased by 95%, compared to virtually no capacity in this segment in 2023.
Other regulatory developments
The blackout also led to improvements in system monitoring and control. New mechanisms and protocols now require greater transparency and real-time data exchange between all participants in the electricity system. The supervisory powers of the National Commission for Markets and Competition (CNMC) have been strengthened and operational procedures have been updated to enable renewable power plants to implement controlled ramp-up and ramp-down processes to avoid cascading failures.
In addition, renewable producers are now increasingly able to provide voltage regulation through grid-forming capabilities – an important step that has long been advocated by the industry.
On the infrastructure side, the Ministry for Ecological Transition and the Demographic Challenge (MITECO) launched its proposal for the electricity transmission network 2025-2030 shortly after the power outage. The plan prioritizes around €13.6 billion in investments to integrate renewables, improve interconnections and support industrial electrification, with the aim of reaching an 81% share of renewables in the energy mix by 2030.
Measures have also been introduced to accelerate electrification. A royal decree approved in November 2025 promotes the connection of new economic activities – especially industrial ones – to the grid. It also introduces a five-year expiry period for grid access rights to prevent speculation and hoarding, and shortens response times for distribution network extensions, including those related to EV charging infrastructure.
Excellent challenges
Despite progress in the implementation of renewable energy sources, more than 70% of Spain’s total energy consumption is still dependent on fossil fuels. According to the Renewable Energy Foundation, imports of gas and oil alone cost more than €51 billion last year. Reducing dependence on gas and accelerating electrification in the transport, industrial and heating sectors remains a crucial priority.
Grid limitations also remain a major problem. Although there was strong renewable energy generation by 2025, saturation issues also emerged that forced curtailments. On average, 3.11% of renewable electricity could not be integrated into the grid, with peaks of more than 10% in July. A total of 5,414 GWh of sustainable electricity was curtailed.
At the same time, Spain recorded a new high in negative electricity prices, with 397 hours of negative prices in the first quarter.
Negative consequences
An unintended consequence of the power outages is the increased reliance on gas-fired power generation to stabilize the electrical grid. Red Eléctrica activated strengthening measures based on combined cycle gas turbines, leading to a 50% increase in gas-fired generation between May and December 2025. As a result, CO₂ emissions from the energy sector increased by 9% year-on-year, equivalent to an additional 2.44 million tons of CO₂, according to the Sustainability Observatory.
System costs have also increased significantly. According to the Observatory of Operating Service Costs, operating costs have reached €1.8 billion so far this year. The additional service costs increased from €0.017/kWh in February 2025 to €0.029/kWh in February 2026. However, in recent weeks these costs have decreased slightly as more renewable generators start providing voltage regulation services.
The power outage also underlined Spain’s limited interconnection with the rest of Europe. A year later, cross-border exchange capacity still represents only around 4% of installed generation capacity – well below EU recommendations.
However, progress is happening. In 2025, construction began on the Bay of Biscay submarine link with France, a 400 km link that will increase exchange capacity from 2,800 MW to 5,000 MW. More recently, MITECO signed a Memorandum of Understanding with Ireland to explore a new submarine interconnection.
Responsibilities and investigations
The CNMC has taken its first administrative steps after nearly a year of investigating the power outage. On April 17, it launched twenty sanctions proceedings: one very serious case against Red Eléctrica and 19 serious cases involving assets owned by Endesa, Iberdrola, Naturgy, Repsol and Bahía de Bizkaia Electricidad.
The regulator has since expanded its investigation to include 35 additional cases – mainly involving Endesa and Iberdrola – some of which relate to incidents dating back two years and not directly linked to the blackout. The CNMC now has up to 18 months to complete its investigations and impose sanctions where necessary.
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