Madrid, 14 September 2026. Spain's battery storage market is moving into a new phase, transitioning from development to construction. Return, an independent energy storage solutions provider, has reached financial close and started construction of its first storage portfolio in the country. The three projects are located in the province of Biscay in the Basque Country (Güeñes, Barakaldo and Lezama) and have a combined capacity of 55 MW / 220 MWh, making this the largest standalone battery energy storage portfolio in Spain to have secured bank financing and entered construction.
“This milestone demonstrates that battery storage in Spain has become an investable infrastructure asset,” says Steve Sceery, Director of Return Spain. “We have brought together the long-term revenue model, financing, technology and execution capabilities required to bring these projects into construction. It is an important step for Return in Spain and another key building block of our European storage platform.”
Why battery storage matters more now
Renewable electricity generation in Spain continues to grow and, with it, the need for flexibility. Battery storage makes it possible to capture electricity when solar and wind generation is high and release it when the grid needs it most. In this way, it helps balance supply and demand and maintain the stability of the electricity system. It also allows more renewable energy to be used instead of having to curtail it when the grid is unable to absorb it.
The importance of flexibility has become even more evident in recent months. Disruptions to Spain’s electricity grid have pushed system resilience and flexibility higher up the national agenda, reinforcing the need for storage infrastructure alongside the continued growth of renewable generation.
The 55 MW / 220 MWh scale means that the batteries will be able to provide 55 megawatts of power simultaneously and sustain this output for approximately four hours before needing to recharge. The three projects will help strengthen the electricity grid around Bilbao and support the wider region in absorbing and using a greater amount of renewable energy as generation continues to grow.
From development to construction
The start of construction demonstrates Return’s integrated model: developing battery storage facilities, bringing together the commercial, financial and execution partners needed to build them, and retaining long-term ownership and operation of the assets.
A key part of this model is Return’s ten-year energy offtake agreement (tolling) with ENGIE, announced last month. It is the first agreement of its kind in Spain and provides long-term revenue visibility, while ENGIE manages the batteries’ output across Spain’s energy markets.
Return has secured the financing and agreements required to begin construction. Rabobank has provided 50 million euros for construction and other credit guarantees; CATL is supplying the battery technology and long-term maintenance services, while Spanish contractor Enerland is delivering the projects on the ground.
During construction, the portfolio is expected to support around 50 local full-time positions.
“Battery storage is becoming a fundamental component of modern power systems,” says Jean-Nicolas Lejeune, Managing Director of Supply and Energy Management activities at ENGIE Iberia. “Our agreement with Return provides this portfolio with the revenue visibility it needed to reach financial close and is exactly the kind of long-term collaboration that enables projects like these to get built.”
“Battery storage is rapidly emerging as a critical enabler of the energy transition, and this transaction marks an important milestone for the Spanish energy market,” says Carol Kort, Executive Director of Project Finance at Rabobank. “Thanks to our extensive experience financing renewable energy and energy storage projects across Europe, we are delighted to partner with Return in bringing its first battery storage portfolio in Spain into operation.”
Building Return’s European storage platform
Construction of the three projects is already underway, and commercial operations are expected to begin in the second half of 2027. Spain is one of Return’s priority markets, as the rapid growth of renewable generation is increasing the need for flexible capacity. This portfolio marks Return’s transition from development to construction in Spain and demonstrates its ability to take battery storage projects through their entire lifecycle: from development and commercial structuring to financing and construction, through to long-term ownership and operation.
Spain also represents the latest step in Return’s expansion across Europe. By applying the same integrated model across different markets, Return is building a pan-European platform of flexible energy infrastructure capable of supporting the continued growth of renewable electricity generation.
