The rapid expansion of renewable energy has created a well-known problem: solar and wind generation often peak when electricity demand is low. Grid-scale battery storage is the standard answer, yet the largest distributed storage resource already exists—millions of electric vehicles parked daily. Their high-voltage batteries remain idle for most of the day, representing an enormous, largely untapped buffer for clean power that could ease strain on transmission networks and sharply reduce household energy bills.
The Scale of Mobile Storage
Data from RWTH Aachen University puts the opportunity into perspective. According to Mark Junker, a department head at the university, EV batteries currently account for a combined storage capacity of roughly 120 gigawatt-hours. By comparison, stationary home storage systems and utility-scale battery installations together reached only 25 GWh at the start of 2026. The electric vehicle fleet therefore already delivers a capacity several times larger than dedicated stationary assets. Unlocking it, however, demands more than just a bidirectional EV: a compatible home wall box and an intelligent home energy management system (HEMS) are equally essential.
How Owners Benefit and the Two Paths to the Grid
For private drivers, the equation is straightforward—feeding stored energy back into the grid turns an electric car into a revenue-generating asset. Pilot projects are now advancing in markets such as Germany, where automakers and energy suppliers are testing both vehicle-to-home (V2H) and vehicle-to-grid (V2G) configurations. In a V2H setup, the car supplies electricity directly to the owner’s home, maximizing self-consumption from rooftop solar panels. V2G extends this logic outward: EVs collectively operate as a virtual fleet battery for the public grid, absorbing surplus wind and solar generation and discharging it during periods of high system load.
The Standards Falling into Place
The technical foundation required for mass adoption is already defined. The ISO 15118 standard for bidirectional charging provides the common framework, and from January 1, 2027, it will become a binding legal requirement for all new private and public charging points, including home wall boxes. Carine Chardon, managing director of the German industry body GFU Consumer and Home Electronics, describes this as a decisive moment: “The EV as an energy storage system was long a vision of the future that is now becoming reality. Rising demand for electric vehicles is turning e-mobility into a key pillar of the energy transition.”
Complementing ISO 15118, the open EEBUS control standard—specifically tailored to electric vehicle supply equipment—enables cross-manufacturer communication within smart buildings. The remaining obstacle is seamless interoperability between car manufacturers and charging infrastructure operators, ensuring electricity can be fed flexibly into diverse grids. Once that final coordination step is taken, activating the giant 120-gigawatt-hour battery waiting outside front doors becomes a practical proposition.
Source: gfu.de