V2G

An ordinary charger moves power one way, from the grid into the car. A V2G charger can reverse the flow. The EU's AFIR regulation defines bi-directional recharging as "a smart recharging operation where the direction of the electricity flow can be reversed, allowing that electricity flows from the battery to the recharging point it is connected to."

One car makes little difference to the grid. The value comes from aggregation: a platform pools hundreds of vehicles that are parked and plugged in, treats them as one flexible resource, and offers that resource to a market or a grid operator. When the grid needs power or frequency support, the platform tells chargers to slow charging or discharge. When power is cheap or in surplus, it charges. Nuvve has run V2G continuously in Denmark since September 2016. For November 2023 the company reported 24.2 MW of EV charging and storage capacity under management, up 39% year on year.

The car and the charger have to agree on every change in direction and power. ISO 15118-20:2022, the second generation of the vehicle-to-grid communication interface, defines the messages and their sequence for bidirectional power transfer between the vehicle's communication controller and the charger's, over IP. Above the charger, the backend platform sends setpoints to each charge point and collects meter data.

A V2G product is at least three systems that have to agree with each other. Charger firmware handles ISO 15118 with the car. A backend controls the chargers and meters. An aggregation platform decides, every few seconds or minutes, how much each vehicle charges or discharges. Your supplier should state which of these they build and which they integrate.

The aggregation platform carries most of the business logic. For each vehicle it has to know when it was plugged in, when it is expected to leave, its state of charge and the minimum charge the driver needs at departure. From that it forecasts how much flexibility the fleet can offer in each hour, prepares bids, and splits accepted volumes into setpoints per charger. After delivery it has to prove what happened: metered energy per vehicle, response times and reports that settlement and the driver's payout depend on.

Data consolidation is slow, detailed work. Charger telemetry, fleet records and grid or market signals usually live in separate systems with different identifiers and clocks. Until they sit in one model, nobody can calculate earnings or answer a grid operator's query about a past event.

The driver or fleet manager also needs an app that sets departure times and minimum charge, shows charging and discharging history and explains earnings. If drivers do not trust it, they unplug, and the fleet's available capacity shrinks.

AFIR applies from April 13, 2024. It requires publicly accessible recharging points built after April 13, 2024, or renovated after October 14, 2024, to be capable of smart recharging. Article 15(4) asks each national regulator to assess, by June 30, 2024 and every three years after that, how much bidirectional recharging could reduce user and system costs.

Delegated Regulation (EU) 2025/656 adds communication standards to AFIR. Public charging points installed or renovated from January 8, 2026 must comply with EN ISO 15118-2:2016 and its companion parts. From January 1, 2027 new or renovated public points must comply at least with EN ISO 15118-20:2022, and points that offer automatic authentication such as plug and charge must support both -2 and -20. Private Mode 3 and Mode 4 points installed or renovated from January 1, 2027 must also comply with EN ISO 15118-20:2022. For a V2G buyer this means that most chargers installed in the EU from 2027 have to speak ISO 15118-20, the protocol version that carries bidirectional power transfer.

We worked with Nuvve, which reports a V2G network of more than 700 EV chargers and storage units on three continents, from January 2022 to December 2023 on a time-and-materials contract. In the first phase a five-person team automated monthly customer reporting, which had been calculated by hand, and built a tool for monitoring and bidding on the Danish energy market. The tool first analyzed daily energy data, predicted next-day prices and recommended trading strategies, and later placed real bids through an API. We also built a database that brings charger, fleet and grid data into one place. The work included integrating new charger makes and models with Nuvve's platform; the vehicle-to-charger protocol itself runs in charger firmware and was not part of our scope.

In the second phase, between January and April 2023, a team of nine rebuilt Fleetbox, the app fleet operators use to manage charging and market participation, including discharging back to the grid. It shipped on web, iOS and Android and replaced the old app in EU and US markets. The stack was Python, Django, Django REST Framework and Celery on the backend, React, Next.js and React Native on the frontend, with PostgreSQL, Redis and WebSocket for real-time data.