The Electric Car as an Energy Storage System on Your Doorstep 

Frankfurt am Main, July 9, 2026 – In the course of the day, energy from renewable sources is not always available when demand for energy is high. These gaps can be offset by energy storage systems. The success of the energy transition therefore also depends on a sufficiently large capacity of energy storage systems. Grid operators and energy suppliers are currently building battery storage systems with large capacities in order to make the fullest possible use of the renewable energy generated and save fossil fuels.

However, many storage systems do not need to be built from scratch; they already exist and their number is constantly growing: the batteries of electric vehicles. In everyday life, cars are parked unused for a large percentage of the day and could therefore be used for the temporary storage of energy – for example, self-generated energy from photovoltaics. This helps relieve the burden on grids and contributes to lowering energy costs for households. According to Mark Junker, Head of the Department of Grid Integration of Batteries and Storage System Analysis at RWTH Aachen University, this already represents a “very, very relevant contribution” of currently around 120 gigawatt hours of storage capacity. This is many times the capacity of stationary storage systems, which is around 25 gigawatt hours (as of early 2026, according to RWTH Aachen University). Prerequisite: The electric car and the wallbox must be suitable for bidirectional charging, and an intelligent home energy management system (HEMS) is needed for control.

Automobile manufacturers and energy suppliers have already launched or announced pilot projects in which owners of electric cars can earn money by making their batteries available as energy storage systems. When the car’s battery is used, this is referred to as “V2H – Vehicle to Home” or “V2G – Vehicle to Grid”. With “V2H”, the car feeds the stored energy into the home for use, while with “V2G” the energy is fed into the power grid. “V2H” optimizes self-consumption, for example of the renewable energy produced by one’s own photovoltaic system. With “V2G”, the batteries in electric cars serve as “swarm storage” and can absorb overproduction from solar and wind power and then feed it back into the grid when demand is high.

The technical requirements are, in principle, already available. The basis for this is the ISO-15118 standard for public charging points. It will become mandatory for all private and public charging stations from January 1, 2027.

For example, the so-called “EEBUS” offers control solutions for these applications, especially for the charging infrastructure for electric vehicles (EVSE). “EEBUS” is an open, manufacturer-independent communication standard for intelligent energy management in buildings. One current hurdle is the ability to feed the stored energy into different grids as well. Here, a joint solution between automobile manufacturers and the operators of charging infrastructure must be found so that the immense storage capacity of electric cars can be used effectively for the energy transition.