Modern cars, especially electric ones, are packed with features. Recently, here in Copenhagen—where I now permanently reside—I had the chance to test the Kia EV3 (full review here). It’s one of those cars that promises functionalities like V2L (Vehicle-To-Load, easy to try out since it allows you to power appliances or other vehicles) and V2G, the ability of a vehicle to feed electricity back into the grid.
This technology was a major topic at EVision 2025, an event co-sponsored by NordiskBil as well, and is seen as a potential solution to avoid overloading the grid at a time when more and more devices—including cars—are drawing power from it. Yet, it’s also one of those features that’s very difficult to test when using a press vehicle, as it’s not widely implemented yet.
A (Partially) Failed Attempt
Knowing I’d be test-driving the Kia, we teamed up with Spirii and DTU, to try it out and to dive deeper into V2G—its potential and current limitations. One of the issues (spoiler alert) comes from the car’s own software. Together with Lisa Calearo, Senior R&D Engineer at Spirii, we arranged a test session at DTU, where a research team under the supervision of Mattia Marinelli, Professor in the E-mobility and Prosumer Integration section, is dedicated to Vehicle-To-Grid technology.
“I work in the Future Tech department, where we collaborate with partners across Europe—and beyond—to develop innovative, mid- to long-term solutions. We’re not just thinking about tomorrow, but about how the sector will evolve in one, two, or five years,” Lisa explains. “We work closely with universities and research centers and are involved in several European R&D projects, like AHEAD, FLOW, and the Danish project e2flex. Our goal in these projects is to improve energy management, exploring concepts such as smart charging, V1G (unidirectional charging), and V2G (bidirectional charging),”
The test showed that the car recognized the test grid set up by the team, but after just a few seconds it cut off the energy flow. The reason? Kia’s own software intervened to prevent potential issues or even cyberattacks.
“It seems the implementation of the ISO 15118-20 standard was there, but the communication via TLS wasn’t happening as expected. TLS is a security protocol: it encrypts communication between the vehicle and the grid to prevent cyber threats. It’s a kind of digital handshake, like exchanging a password, which must succeed in order to authorize bidirectional charging,” Lisa explained.
V2G, V2B, V2L, V2X: Let’s Clear Things Up
Before diving into V2G, it’s worth understanding what the different acronyms mean—terms that will increasingly become part of how car manufacturers communicate, as more modern vehicles begin to support these functions. This is a technology not only backed by the Hyundai Group but also by former CEO Luca De Meo at Renault, who has pushed for its integration into the Renault 5 E-Tech and even the upcoming new Twingo.
When we talk about Vehicle-to-Grid (V2G), we mean a system where an electric car not only draws energy from the grid (as happens during standard charging) but is also capable of sending energy back into it. This is a bidirectional process. Why is it useful? The grid operator (such as Energinet in Denmark or Terna in Italy) must maintain a balance between energy production and consumption. If production exceeds consumption, the grid frequency rises; if consumption is too high compared to production, the frequency drops. Ideally, this frequency needs to remain around 50 Hz.
In this context, your car can help:
- When there’s too much production, the car can absorb energy (i.e., charge) to stabilize the grid.
- When there’s too much demand, it can feed energy back into the grid, acting as a small energy provider.
This is the core idea behind V2G: using cars as a resource to help stabilize the grid.
When it comes to V2L (Vehicle-to-Load), the concept is simpler: using the car’s battery to power external devices, such as a computer, a lamp, or a camping fridge. “It’s a system designed for small loads and typically has a limit of around 3 kW. It works thanks to an integrated inverter in the car, which converts the battery’s direct current (DC) into alternating current (AC) that your devices can use,” explains Calearo.
Then there’s V2B (Vehicle-to-Building), which is similar to V2G but with one key difference: the energy is not sent back directly into the public grid, but into a specific building (a house, an office, etc.). “A practical example: if you have solar panels on your roof, you can charge your car during the day and then use the battery stored energy to power your building when the panels stop producing.”
A subset of V2B is Vehicle-to-Home (V2H), specifically for private homes. It works the same way: using the car’s battery to power your home when needed—such as in the evening or during a blackout.
Finally, the term Vehicle-to-everything (V2X) is often used to describe all these modes: V2G, V2L, V2B, and V2H. “In the electrical field, the ‘X’ stands for any system to which energy can be transferred from the car’s battery. More generally, V2X is also used to describe all vehicle interactions, including for example vehicle-to-vehicle (V2V) communications,” concludes Lisa.
And What About Traditional Charging?
In the case of unidirectional charging (the classic one), even here, smart features can be implemented. For example, you can modulate charging power based on the output of your solar panel system: if the sun is shining, you charge more; if production drops, you reduce the power. This is named vehicle-one-grid (V1G) or smart charging.
The Battery Question
At this point, we need to understand what it means for a car battery to be subjected to these kinds of uses. Yes, it’s true that when you use your car’s battery to provide services to the grid—like with the V2G technology—you’re actively using the battery, which could potentially accelerate its degradation. But not drastically.
“During my PhD, we ran some tests in Frederiksberg (a municipality enclave within Copenhagen) on Nissan vehicles, which at the time were among the few to support vehicle-to-grid. We monitored battery degradation by measuring residual capacity every six months. The results showed that the additional degradation caused by frequency regulation was minimal, accounting for only a few percentage points of the total degradation. In other words, the impact was limited—at least in that context,” explains Lisa. She adds that degradation depends on many factors, such as battery chemistry, the amount of energy exchanged, power levels, temperature, driving habits, and charging methods.
Moreover, not all grid-related applications wear down the battery in the same way. High-frequency regulation services (where power fluctuates every second) are more demanding, while others require slower variations and are therefore less stressful on the battery.
Starting with Fleets Makes Sense
At this point, I asked Lisa about the actual benefit of Vehicle-To-Grid. We know a technology can have great potential, but it has to be economically viable for it to gain traction. My example was the case of EVs in Denmark: here, for about a decade, the government eliminated taxes on battery vehicles, making them far more affordable than gasoline or diesel cars, which are heavily taxed. “From the citizen’s perspective, bidirectionality (the ability to both charge and discharge energy from the car battery) offers several benefits,” says Lisa. “For example, you can use your car as a backup power source in case of a blackout. If you’ve charged your battery during the day—perhaps using solar panels—you can use that energy in the evening to power your home.”
Lisa also points to the economic aspect: individuals could provide services to the grid and participate in balancing the energy system. “Today, this type of usage on at the household level presents challenges, such as efficiency losses, technical and economic obstacles, and it is still unclear whether it is truly beneficial for a single user. However, there is significant potential in batteries parked at home overnight, which should be somehow harnessed to maximize the benefits of this technology.”
But while it may not be worthwhile for private individuals, it’s a different story for fleets or industrial vehicles. “If you’re managing dozens or even hundreds of vehicles—or ones with large 500 kWh batteries, like electric buses—it becomes much easier to enter the energy market and provide these services efficiently”
I pointed out to Lisa that, both in Copenhagen and in Milan, most people don’t have access to solar panels. “Well, even public infrastructure could be integrated,” she replies. “If public charging stations became active participants in providing grid services, users could, for example, receive discounts on the final charging bill. The issue is, this all requires a perfectly integrated ecosystem, and today there are still many barriers—not just technological, but also regulatory.”
Each country has its own grid code—a set of technical and operational standards that define the connection and operation of electrical equipment and systems to the electricity grid. “In EU, there is harmonization, however, each country can add additional specifications. For instance, before you can use a bidirectional charger for V2G, the inverter—whether it’s inside the car (for AC charging) or in the station (for DC charging)—has to be approved under that country’s grid code. In Denmark for example, the inverter manufacturer could simplify the process by certifying the component to the ‘positive list,’ a registry of authorized devices. However, doing this for every charger—or even for every car model—can become incredibly complicated.”
About Spirii
Founded in 2019 in Copenhagen, Spirii is a provider of comprehensive electric vehicle charging solutions, operating in 22 markets. At the core of its services is Spirii Connect, an all-in-one charging station management platform that enables charging infrastructure operators and fleet managers to monitor and monetize their charging networks.
Spirii’s end-to-end services cover every stage of the process: from energy and grid management to hardware sales and logistics, as well as installation, project management, operational support, billing, and payment solutions—ensuring a smooth and hassle-free transition to electric mobility.
To support EV drivers on the go, the Spirii charging app provides roaming access to over 600,000 charging points across two continents, making navigation, charging, and payment simple and intuitive. Spirii operates across various sectors, including transport and logistics, corporate fleets, real estate, retail, energy, and utilities. Its client portfolio includes well-known names such as Circle K, Shell, Audi, TotalEnergies, EDF, NCC, UTA Edenred, HelloFresh, Radisson, and many others. Beyond its commercial offerings, Spirii is committed to shaping the future of electric charging through innovative research projects. It actively participates in EU-funded initiatives like FLOW and AHEAD. In February 2024, Spirii was acquired by Edenred.
