Spain’s Grid Historic Imbalance as Solar Surges Ahead of Demand
Spain’s record-breaking curtailment volumes in July 2025 mark a pivotal moment for the energy market. With a more complete view of the summer data, the scale and persistence of the imbalance are becoming increasingly clear. As generation continues to outpace demand, the system is entering a phase of structural oversupply.
This trend is expected to accelerate unless large-scale flexible loads such as data centers, industrial hubs, or green hydrogen projects begin to absorb the surplus and contribute to grid stability.
The clearest indicator of this growing imbalance came on July 28, 2025, when the Spanish electricity system recorded an all-time high of 87.5 GWh assigned to Phase I downward redispatch due to technical constraints.
This massive volume of curtailment far exceeded previous highs, including 54 GWh on July 4, 2025 and nearly 50 GWh in October 2023. The historical trend (first image) clearly shows a sharp acceleration in curtailments in recent months.
With more than 990 GWh curtailed, July 2025 surpassed all previous Julys. By the end of the month, total cumulative daily redispatch had exceeded 1,000 GWh, marking an unprecedented level.
The hourly profile reveals a familiar yet increasingly concerning pattern. Curtailment begins ramping up around 08:00, peaks between 12:00 and 15:00 with hourly volumes exceeding 8 GWh, and gradually tapers off into the evening. This curve mirrors the daily solar generation peak, confirming that PV remain the most impacted technology.
At these volumes, curtailment is no longer an occasional anomaly, it has become a systemic, structural feature of the Spanish grid. The implications are far-reaching:
- Revenue losses for merchant PV plants and PPA-backed projects
- Need for grid-aware modeling, including nodal congestion and localized flexibility
- Opportunity cost of wasted clean energy during peak solar hours
- Urgent need for storage deployment and dynamic grid operation strategies
This environment reinforces the importance of granular, node and province level impact assessments to determine how specific assets are affected and what mitigation strategies are viable. These may include:
- Optimizing BESS sizing
- Transitioning to flexible hybrid operation models
- Redesigning market bidding strategies to adapt to congestion signals
Approximately 45% of this curtailment has affected solar assets and around 42% has impacted wind generation, with the remainder distributed across other technologies. This distribution highlights the disproportionate exposure of variable renewables to structural grid constraints, intensifying the urgency for targeted mitigation strategies.
As a result, many assets have begun to shift their primary revenue sources towards REE’s ancillary services (SSAA), leveraging flexibility and availability payments to offset curtailed energy volumes. This trend underscores the growing relevance of system services markets as a complementary or even dominant income stream for renewable and hybrid assets operating in Spain.
The deployment of large-scale BESS and the accelerated build-out of data centers are expected to materially modify demand profiles, creating additional levers for congestion relief and enhancing overall grid flexibility.
