21.56 MW Battery in Esquivias: Key insights for the solar sector in Toledo

Key data

Mulhacén Solar, SLU can now execute its energy storage module of 21.56 MW in Esquivias (Toledo) after receiving prior administrative authorization from the General Directorate of Energy Policy and Mines, published in the BOE on October 12, 2026. The resolution, signed on September 7, 2026, enables hybridization of this battery with the Mulhacén Solar photovoltaic plant, already operational with 70 MW of installed capacity.

The authorization is based on RD 997/2025 and Law 24/2013 of the Electricity Sector, and is granted without prejudice to other sectoral authorizations that the promoter must obtain. For the renewable sector, this resolution is a clear signal that the administration is streamlining solar-storage hybridization procedures in Spain.

What does this regulation establish?

The resolution grants prior administrative authorization for the project called "Mulhacén energy storage module," along with its evacuation infrastructure. The key technical and regulatory elements are as follows:

A notable aspect is that evacuation takes advantage of already authorized infrastructure, which reduces administrative complexity and execution timelines. Connection to the Numancia 4 substation at 30 kV via underground lines is the technical solution chosen to integrate storage into the existing network.

Economic and operational impact

Hybridization of a 21.56 MW battery with a 70 MW solar plant has direct operational and economic implications for Mulhacén Solar, SLU and serves as a model for the sector:

• Revenue optimization: The battery allows storing energy generated during low-demand hours and releasing it to the grid during peak hours, improving average selling price.
• Reduction of spillage: In large photovoltaic plants, storage prevents generated energy from being wasted when the grid cannot absorb it.
• Leveraging existing infrastructure: By using evacuation lines and access permits already authorized (updated by Red Eléctrica in November 2023), the promoter avoids costs and additional timelines for new connections.
• Environmental agility: Passing simplified environmental impact assessment without ordinary procedure shortens the startup calendar and reduces regulatory uncertainty.
• Consolidated regulatory framework: RD 997/2025 and Law 24/2013 provide a predictable framework for structuring financing of hybridization projects.

Who does it affect?

• Mulhacén Solar, SLU: Direct holder of the authorization and responsible for executing the project.
• Renewable energy promoters in Castilla-La Mancha: The resolution establishes a precedent on how to process solar-storage hybridizations under RD 997/2025.
• Investors and renewable funds: The authorization confirms the regulatory viability of storage projects associated with existing photovoltaic plants in Spain.
• Legal and technical advisors in the energy sector: Must understand the simplified environmental assessment procedure and updated access and connection requirements by Red Eléctrica de España.
• Network operators and substations: Red Eléctrica de España, as manager of the transport network in Torrejón de Velasco (400 kV), and operators of the Numancia 4 substation.

Practical example

A promoter already operating a 70 MW photovoltaic plant in Toledo province and wanting to add storage can follow the path traced by Mulhacén Solar:

1. Request update of access and connection permits from Red Eléctrica de España — in Mulhacén Solar's case, this step was completed in November 2023.
2. Submit the storage module project to the General Directorate of Energy Policy and Mines, under RD 997/2025 and Law 24/2013.
3. Opt for simplified environmental impact assessment if project characteristics allow, avoiding ordinary procedure and shortening timelines.
4. Design evacuation via underground lines at 30 kV connected to an existing substation, leveraging already authorized infrastructure up to the transport network.

In Mulhacén Solar's specific case, the 21.56 MW battery represents approximately 30.8% of the power of the 70 MW photovoltaic plant, a typical proportion in hybridization projects seeking to balance investment cost and energy management capacity.

What should companies do now?

1. Review if you have photovoltaic plants susceptible to hybridization: If you operate solar installations in Spain, analyze whether adding storage improves your profitability and if your access and connection permits are up to date.
2. Verify the status of your access and connection permits with Red Eléctrica de España: They are an essential prerequisite for any hybridization request under RD 997/2025.
3. Study the simplified environmental assessment route: If the project does not exceed thresholds requiring ordinary procedure, this route significantly shortens authorization timelines.
4. Leverage already authorized evacuation infrastructure: Connecting the storage module to existing lines and installations reduces costs and additional procedures.
5. Consult the RD 997/2025 and Law 24/2013 framework: These are the regulations governing the prior administrative authorization procedure for this type of project in Spain.
6. Follow regulatory developments in Castilla-La Mancha: The region concentrates a relevant portion of installed photovoltaic capacity in Spain; regional and state resolutions in this community set trends for the rest of the territory.

Official source

Consult complete regulation at official source

Notice: This article is purely informational in nature and does not constitute legal advice. For specific decisions, consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-21226