Electricity transmission grid facilities

In financial year 2025, which was marked by a high degree of uncertainty in the global political landscape, international trade, and economic policies, investment in the transmission grid increased to €1.424 billion, a 45.9% rise compared to the previous year. These investments are included in the current 2021–2026 Electricity Planning and have helped further integrate renewable energy generation into the electricity system, boost interconnection capacity, and strengthen grid meshing, thereby ensuring security of supply and maintaining service quality. Throughout 2025, transmission grid assets expanded by 486 kilometres of circuit and 212 substation bays, bringing the total length of line circuit in the national grid to 46,155 kilometres, a 1.1% increase compared to 2024. In addition, transformer capacity increased by 1,455 MVA, bringing the total installed transformer capacity nationwide to 99,071 MVA (1.5% higher than in 2024).

Facilities in the electricity transmission grid in Spain

Annual evolution of the electricity transmission grid in Spain

Annual evolution of the transmission grid by systems

Among the projects carried out in the transmission grid in 2025, the following are the most important, according to their geographical area of development:

Northwest area: In Castilla y León, the main initiatives focused on Almazán and Montearenas (400 kV), as well as the 220 kV Villarino and Villatoro substations, to strengthen the region’s transmission capacity and its role as a strategic node within the meshed structure of the Spanish electricity system. Additionally, the commissioning of the reactance at Olmedo (400 kV) will improve voltage control in the area.

In Galicia, actions aimed at enhancing capacity, stability and security of supply were undertaken, with notable interventions at the 220 kV Tomeza substation, as well as the commissioning of the statcom at Lousame (220 kV) and the reactance at Sabón (220 kV). Furthermore, progress continued on the northern interconnection with Portugal, with the completion of the Fontefría–Portuguese border and Beariz–Fontefría 400 kV lines.

Northern area: Extensions and refurbishments were carried out in País Vasco, including at Abanto and Gática (400 kV) and La Jara and Vitoria (220 kV). The uprating of the Hernani–Argia and Barcina–Itxaso 400 kV lines was also completed. These projects will strengthen the grid to meet growing industrial demand and improve system reliability.

In La Rioja, the main project was the expansion of the Haro 220 kV substation, with the aim of reinforcing this regional node.

In Navarra, significant extensions were carried out at substations such as La Serna (400 kV) and Tafalla (220 kV), improving the flexibility and robustness of the regional grid.

In Cantabria, the expansion of Solórzano (400 kV) was completed to connect a new reactance. This will improve security of supply through enhanced voltage control, reducing the cost of technical restrictions and enabling the integration of a higher volume of renewable energy generation.

Northeast area: In Aragón, works were carried out on the 400 kV grid, specifically at the Peñaflor, Terrer, Fuendetodos and Escatrón substations, in addition to the commissioning of the new Calatorao 220 kV substation. All these actions have reinforced a key axis of the peninsular system, both in terms of renewable energy evacuation and for meshing.

In Cataluña, multiple upgrades were undertaken on lines and strategic nodes, mainly within the 220 kV grid, including Mangraners, Cerdà, Viladecans, Abrera, and the new Francolí substation. These actions combine extensions, refurbishments, new equipment installations and adaptations, all aimed at strengthening the grid in an area with high demand density and significant penetration of renewable energy generation.

Central area: Several expansion projects have been completed in Castilla La Mancha, including upgrades and refurbishments at 220 kV substations such as Olmedilla, Calera y Chozas and Trillo, as well as Belinchón and Minglanilla (400 kV). The commissioning of a power flow controller at Picón 220 kV is particularly noteworthy. This is designed to manage the increase in renewable energy generation while keeping short-circuit levels and power flows within safe limits.

In Madrid, numerous initiatives have been undertaken to expand capacity, refurbish assets and adapt key 220 kV substations in the metropolitan area, such as San Fernando, Loeches, Pinto, Ciudad Deportiva, Boadilla, Fortuna, Arganda,and Aena. This will help optimise the transmission grid in one of the areas with the highest energy demand in the country. In addition, a statcom has been commissioned at the Moraleja 400 kV substation to improve inter-area oscillation damping.

Southern area: In Andalucía, numerous initiatives have been carried out to reinforce, refurbish, and expand the transmission grid. Key projects include expansions at Costa de la Luz and Benahadux (220 kV), and Baza and Antas (400 kV), as well as the commissioning of the new Guadaira 220 kV substation. Further improvements, upgrades and commissioning of reactances and transformers have been implemented at strategic locations such as Algeciras (220 kV) and Carmona (400 kV). All these actions will help enhance quality of supply, increasing system reliability and improving the integration of new renewable energy generation.

Also noteworthy is the commissioning of the double underground/submarine 132 kV interconnection between Algeciras and Virgen de África, which links the Spanish Peninsula and Ceuta. This project, with a total length of 137.8 km, will significantly improve the security and quality of Ceuta’s electricity system, reduce its generation needs and overall costs, and enable greater integration of renewable energies.

In Extremadura, the modernisation and expansion of existing infrastructure has materialised through works at 400 kV substations such as Don Álvaro, Fuente Maestre, and Zarzón, along with the commissioning of line in/out connections at Maguilla and Don Álvaro (400 kV).

Eastern area: In Comunidad Valenciana, noteworthy projects include expansions at Cofrentes (400 kV) and Sagunto (220 kV), as well as line in/out connections to the new Saguntum 220 kV substation. In addition, upgrades have been carried out on lines and substations linked to renewable integration. These actions consolidate this grid as one of the most important backbones of the electricity system.

The new Abanilla 400 kV substation has been completed in the Región de Murcia to enable the connection and integration of renewable energy generation. Additionally, a new line in/out connection at Campos 400 kV from the El Palmar-Rocamora line has been commissioned to increase renewable energy integration and improve local technical restrictions.

Baleares: Actions have focused on reinforcing the island grid, with major interventions in the 220/132 kV grid at substations such as Bessons, Dragonera, Santa Ponsa, and Mercadal. These include substation expansions to provide additional transformation capacity and new substation configurations designed to improve grid stability, incorporating batteries and compensation systems that will optimise demand management and facilitate the energy transition in the Islas Baleares system.

Canarias: A wide range of projects has been implemented to modernise and reinforce the grid across all islands. Key actions include upgrades to the 66 kV grid at Gran Tarajal, Matas Blancas, Los Olivos, Telde, and Aldea Blanca, as well as new substations at Chío, San Isidro, and El Palmar (La Gomera), in addition to improvements on strategic 66 kV lines such as El Rosario-Guajara, Geneto-El Rosario, and San Isidro-Granadilla. These investments are essential to guarantee security of supply, increase renewable penetration, and enhance the resilience of the Islas Canarias’ electricity system.

Moreover, the interconnection between Tenerife and La Gomera has been completed via a double underground/submarine 66 kV link with a total length of 84.8 km. This interconnection will enable the integration of the previously independent electricity systems of La Gomera and Tenerife, enhance quality and security of supply, improve the efficiency of electricity generation, and allow for greater integration of renewable energies.

Interconnections continue to play a key role in the energy transition to achieve greater integration of renewable energy sources and progress in decarbonisation. Strengthening international interconnections remains a priority in the development of the transmission grid under the current 2021–2026 Planning framework, and is also a key priority at European level, as evidenced by the publication of the European Grids Package by the European Commission in December 2025.
The latest interconnection commissioned between the electricity systems of Spain and France (Baixas-Santa Llogaia) at the end of 2015 doubled the electricity exchange capacity between Spain and France (from 1,400 MW to 2,800 MW), helping to reinforce the security of the two electricity systems and favouring the integration of a greater volume of renewable energy. However, despite this extension, the degree of interconnection in Spain remains below the targets set by the European Union, of 10% and 15% for 2020 and 2030 respectively.

The Spanish National Energy and Climate Plan (NECP) made this clear and proposed increasing the exchange capacity with Portugal to 3,000 MW and with France to 8,000 MW, by means of 3 new electricity interconnections. These objectives were confirmed in the latest revision of the NECP, approved in 2024. The interconnection between Gatika (Spain) and Cubnezais (France) will be the first fundamentally submarine interconnection between Spain and France (the ‘Bay of Biscay’ project); and two other projects across the Pyrenees (Navarra – Landes, and Aragón – Marsillon).