Barcelona has transformed its subway into a distributed power station, harnessing regenerative braking to generate energy from every slowdown. When a train decelerates, the kinetic energy that would typically dissipate is converted into electricity. The project, known as metroCHARGE, was launched with four electric vehicle charging stations, or “electrolineras,” distributed throughout the city.

Currently, about one-third of this recovered energy is reused to power the trains, while the surplus supports lighting, escalators, and EV charging stations across the city. This system expands the urban charging network without requiring new infrastructure, making it a model for cities worldwide and redefining the role of public transport as a driver of the sustainable transition.

While other cities such as Vienna, Philadelphia, and São Paulo have adopted similar systems, Barcelona’s model stands out for extending the recovered energy beyond the railway network, integrating it into EV charging infrastructure. In Vienna, regenerated electricity is used exclusively for trains; in São Paulo, it covers about 15% of the metro’s energy needs. In contrast, Barcelona uses the surplus energy to power urban services and accelerate the transition to electric transportation.

It is estimated that this system could cover 41% of the subway’s energy needs, reducing CO₂ emissions by approximately 3,885 tons per year, turning wasted energy into a renewable resource for urban mobility—a self-sustaining circuit with the potential for further expansion.

TMB is already exploring integrating the system into trams and buses and assessing the combination with solar panels and wind turbines, taking public transport to a new level: not just a mobility network, but also a renewable energy source. Today, the challenge is to reverse the process—not just to consume energy, but to recover it.