Spain has authorised construction of the Los Guájares pumped-storage hydropower project in Granada province. The project will generate 356.93 MW and provide 363.99 MW of pumping capacity.The project highlights the growing importance of energy storage in addressing Europe’s electricity price fluctuations.
MITECO announced the approval on 28 October 2026, following its publication in Spain’s Official State Gazette. The facility will store 1.47 GWh of energy and connect to the grid through a 220 kV transmission line.
Hidroeléctrica Los Guájares SLU is the authorised project company. The developer previously operated under the name Villar Mir Energía and is associated with MOWE, a Spanish renewable energy company.
The project received a favourable environmental impact assessment in August 2025. It has now secured both prior administrative authorisation and construction authorisation. However, the approval does not establish that physical construction has already started.
The development is intended to strengthen Spain’s electricity storage capacity as renewable energy generation expands. The facility will pump water to an upper reservoir when electricity is available and release it through turbines when demand rises. Therefore, it will help balance electricity supply and demand while improving the integration of variable wind and solar power.
Los Guájares Hydropower Project Location and Engineering Design
The Los Guájares project is located around the Rules Reservoir in Granada province, Andalusia. The project spans Vélez de Benaudalla, El Pinar and Los Guájares. Its environmental assessment also references Padul in relation to the wider project and associated infrastructure.
The principal facilities will be built along the right-hand slope of the Rules Reservoir.
The scheme will use the existing Rules Reservoir as its lower water storage point and construct a new upper reservoir. The upper basin will cover approximately 24 hectares and hold about 1.4 million cubic metres of water, including around one million cubic metres of usable volume. Its base and crest will sit at approximately 819 metres and 836 metres above sea level, respectively.
During pumping, electrical energy will drive the pumps to move water from the Rules Reservoir into the upper basin. During generation, water will flow back through the hydraulic system and drive turbines to produce electricity. This reversible process allows the facility to store energy for later use rather than depending solely on immediate electricity generation.
The underground powerhouse will contain two pump-turbine units, transformers, isolation valves and auxiliary equipment in separate underground caverns. The design includes a large hydraulic pressure system to carry water between the reservoirs and the generating equipment.
The main pressurised water conduit will have a diameter of approximately five metres. One section will run through a tunnel for about 470 metres before continuing through a buried trench down the hillside. A further high-pressure section will include a vertical shaft and horizontal section, with an internal diameter of four metres and a combined length of approximately 316 metres.
The design also includes a 100-metre-long surge shaft with a diameter of 12 metres. This underground structure will help absorb pressure fluctuations when the pump-turbine units start, stop or change operating modes. The lower hydraulic conduit will run through a tunnel of approximately 1,092 metres, with a diameter of five metres, connecting the powerhouse to the Rules Reservoir.
Grid Connection And Supporting Infrastructure
The Los Guájares hydropower project will include a dedicated substation and a 220kV overhead transmission line extending approximately 6.46 kilometres from the Los Guájares substation to the Mizán substation. The line will use 24 support structures. The grid connection will allow the plant to import electricity for pumping and export electricity generated during discharge.
Construction will also require access roads, underground galleries and work platforms for installing the hydraulic conduits and electrical equipment. The environmental assessment identifies approximately 11.5 kilometres of access roads for the main plant facilities and about 4.8 kilometres of access routes associated with the transmission-line supports. Some existing roads will be upgraded, while new sections will be required in selected locations.
These works will require coordination between civil engineering, underground construction, hydraulic equipment installation and high-voltage electrical systems. The final construction programme will also need to accommodate the existing reservoir infrastructure and the surrounding terrain.
Investment And Government Support
The Spanish government has awarded the Los Guájares hydropower project €23 million in funding through the Institute for the Diversification and Saving of Energy (IDAE). The grant comes from Spain’s Recovery, Transformation and Resilience Plan and the second competitive funding programme for innovative pumped-storage energy projects. The support is intended to advance energy storage infrastructure and improve the flexibility of the electricity system.
The €23 million award is public funding, not the project’s total construction cost. The reviewed official sources do not disclose a definitive overall capital budget, the main construction contractor or the appointed engineering and project management firms. Those details should therefore be confirmed before publication as established project facts.
Environmental Requirements And Construction Readiness
The project received a favourable environmental impact declaration in August 2025. The assessment includes preventive, corrective and compensatory measures, as well as monitoring requirements for construction and operation. The construction authorisation requires compliance with the environmental conditions and other applicable permits.
The authorities have also identified infrastructure interfaces that need careful coordination. These include the Granada-Motril gas pipeline and other public utilities or services affected by the planned works. The project company has agreed to address the relevant technical conditions. Before works begin, it must also complete specified environmental measures, including flora inventories and wildlife surveys.
The construction authorisation marks a significant step towards delivery. The developer must still comply with the approval conditions and secure any other permissions required for execution. The official resolution also refers to a deadline of 24 June 2032 for meeting the relevant administrative milestone for final operating authorisation for testing. This is not a confirmed commercial operation date.
Once operational, Los Guájares is expected to provide large-scale, dispatchable energy storage for Spain’s power system. Its combination of a new upper reservoir, the existing Rules Reservoir, underground pump-turbine equipment and a high-voltage grid connection will allow electricity to be shifted between periods of surplus and demand. The project will therefore contribute to Spain’s wider effort to integrate more renewable electricity while maintaining grid reliability.
Los Guájares Hydropower Project Fact Sheet
Project: Los Guájares Pumped-Storage Hydropower Plant
Location: Granada province, Andalusia, Spain
Project type: Reversible pumped-storage hydropower and energy storage
Project company: Hidroeléctrica Los Guájares SLU
Developer: MOWE, previously associated with Villar Mir Energía
Generation capacity: 356.93MW
Pumping capacity: 363.99MW
Energy storage capacity: 1.47GWh
Lower reservoir: Existing Rules Reservoir
Upper reservoir: Approximately 24 hectares, with 1.4 million cubic metres of total volume
Grid connection: Approximately 6.46km of 220kV overhead transmission line to Mizán substation
Government funding: €23 million through IDAE
Environmental approval: Granted in August 2025
Main purpose: Energy storage, electricity grid flexibility and integration of renewable generation
Principal Companies and Project Team
Hidroeléctrica Los Guájares SLU : Authorised project company and holder of the administrative construction authorisation.
MOWE :Renewable energy company associated with the development
Spanish Ministry for the Ecological Transition and the Demographic Challenge (MITECO) : Government ministry responsible for the published authorisation.
Institute for the Diversification and Saving of Energy (IDAE) :Public funding body that awarded €23 million to the project.
Red Eléctrica de España :Transmission system operator involved in grid access and connection arrangements.
Junta de Andalucía : Regional authorities involved in environmental, water and infrastructure assessments
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