According to the International Energy Agency (IEA), between 200 and 300 million electric vehicles will be on the roads worldwide by 2030—and the trend is increasing. As a result, their role in smart grids—known as Smart Grids—is becoming increasingly important. Electric vehicles can not only absorb energy but also store it and feed it back into the power grid when needed. This makes them decentralized buffer storage units to balance fluctuations in the feed-in of renewable energies and increase grid stability. The technical basis for this bidirectional energy exchange (Vehicle-to-Grid, or V2G for short) is the communication protocol ISO 15118.
ISO 15118: Technological Enabler for Bidirectional and Smart Charging
As a cross-manufacturer standard, ISO 15118 defines the communication between the e-vehicle, charging infrastructure, and, if available, backend systems such as energy management platforms. As part of the Combined Charging System (CCS), the protocol uses Powerline Communication (PLC) via the charging cable to enable secure and smooth data transmission during the charging process.
With ISO 15118-20, bidirectional charging is fully supported for the first time. This allows electric vehicles to be flexibly integrated into the power grid as decentralized energy storage. In the so-called V1G mode (supported by ISO 15118-2)—that is, during planned, unidirectional charging—the charging process can be shifted to grid-friendly, cost-effective time slots. The system reacts dynamically to signals such as electricity prices, grid load, or user preferences.
The V2G mode goes a step further: here, discharging processes are also enabled. External energy management systems can make decisions based on current and forecasted grid conditions about when and how much energy should be charged or
fed back. Infrastructure and grid operators thus receive a new tool to control grid utilization—such as by deliberately reducing charging power or feeding electricity during peak times.
New Business Models for Fleets
For fleet operators in the logistics sector or public transportation, this opens new business opportunities: the battery capacity of unused vehicles can be temporarily provided to the grid and marketed as a flexibility service.
Furthermore, ISO 15118 enables encrypted communication and standardized automatic authentication—the foundation for convenient Plug & Charge charging processes at public charging points.
Common Standards Create Real V2G Interoperability
For a scalable implementation of V2G, all involved stakeholders must closely collaborate: vehicle manufacturers, charge point operators (CPOs), grid operators, and mobility service providers. The technical basis for this is interoperable standards that allow consistent communication across the entire system landscape.
Three key protocols play a crucial role here:
ISO 15118: regulates the communication between the vehicle (EV) and the charge point (EVSE), including Plug & Charge and bidirectional energy transfer.
OCPP 2.x (Open Charge Point Protocol): regulates the interface between the charge point (EVSE) and the CPO's backend system—and thus serves as a universal "language" for managing charging stations. The version OCPP 2.1 expected in 2025 will also support ISO 15118-20 as well as extended V2X functions such as the integration of decentralized energy sources (DER) and battery swapping.
OCPI (Open Charge Point Interface): standardizes communication between CPOs and E-Mobility Service Providers (EMSPs)—for example, for roaming and service provision across network boundaries.
Real V2G functionality can only be implemented economically and technically sensibly if all three protocols are integrated. The joint
implementation by OEMs, CPOs, and EMSPs creates the necessary interoperability for a scalable, smart energy network. As an experienced partner for software engineering, Intellias supports companies along the entire value chain—from standard compliance to the development of intelligent backend solutions for smart charging and V2G.
The potential role of electric vehicles as active participants in grid stabilization and as decentralized energy storage is obvious—and the technological foundation largely exists. But what about practical implementation in the industry?
V2G Worldwide: Regional Strategies and Challenges
More and more automobile manufacturers are equipping their electric vehicles with ISO 15118, particularly the newer model generations. The V2G capability thus becomes the new standard. However, implementation shows regional differences:
Europe: Here, legal requirements are advancing V2G development—such as through the "Fit for 55" package, the Alternative Fuels Infrastructure Regulation (AFIR), or EU guidelines for the trans-European transport network (TEN-V). Pilot projects in the Netherlands, Denmark, France, and the United Kingdom are currently testing technical and economic feasibility.
USA: The market is organized decentrally. Individual states, utilities, or companies initiate projects. Subsidy programs for EVs and charging infrastructure in some states make V2G more economically attractive—despite the lack of nationwide regulation.
China: As the world's largest EV market, China pursues a state-driven, technology-focused approach. The goal is to use the national EV fleet for grid stabilization, to meet growing energy demand, and to integrate renewable energies. A clear roadmap for V2G has been defined—supported by close cooperation between the government, state grid operators, and the domestic vehicle and battery industry.
Despite different approaches, all markets face similar challenges: high costs for bidirectional
chargers, concerns about battery degradation, and the need for secure, robust communication interfaces.
Infrastructure as a Bottleneck
Charging infrastructure remains a central obstacle: while the vehicle side is rapidly upgrading, a large part of today's installed charging stations still relies on older, incompatible systems. Although some components can be retrofitted with software updates, in many places a hardware replacement will be necessary—with corresponding investment needs and time requirements.
Only a few manufacturers—including Siemens and ABB—currently offer charging solutions with complete ISO 15118 support. Even as open standards like OCPP and OCPI evolve, the path to comprehensive V2G integration is still long.
Practical Insights: V2G Projects Worldwide
Numerous stakeholders are already testing V2G in real-world conditions. Three examples illustrate the diversity of possible applications:
In Utrecht (Netherlands), a fleet of 500 Renault 5s is being used with Mobilize V2G technology in a car-sharing model—a European first.
In Massachusetts, a school district uses bidirectional chargers to buffer peak loads in the summer and generate revenue.
And Ford already enables V2H with the F-150 Lightning through "Intelligent Backup Power." GM plans to introduce V2H for all Ultium EVs by 2026. Nissan continues to rely on V2G and has certified a bidirectional charger from Fermata Energy for 2024.
What Does This Mean?
V2G is seen worldwide as an opportunity and is being implemented in initial projects. Now it's about quickly establishing the necessary framework conditions and standards so that project participants can finally move beyond the pilots—which requires everyone to pull together!
https://www.iea.org/reports/global-ev-outlook-2024/outlook-for-electric-mobility
The research on the topic was conducted for us by Volodymyr Zavadko, Delivery Director, Head of Transportation
