Bidirectional charging: V2L, V2H and V2G explained

In normal charging, power flows from the grid into the battery. Bidirectional means it can flow back out as well. There are three levels, each with its own abbreviation. V2L, vehicle to load, powers individual devices through a socket. V2H, vehicle to home, powers your own house. V2G, vehicle to grid, feeds back into the public grid.

The three sound like stages of one idea, but they differ fundamentally. V2L is a function of the car alone. V2H also needs a suitable charger and a house installation designed for it. V2G needs all of that, plus a grid operator that allows feeding in and an electricity supplier that pays for it. Each level adds parties, and each is therefore less widespread than the one before.

The technical core is the same for all three. The battery supplies direct current; the house and the grid run on alternating current. Somewhere an inverter has to convert, either in the car or in the charger. Where it sits decides which equipment works with which car.

V2L is the simplest form and is available on many newer models. Either the car has a socket in the cabin or the boot, or there is an adapter that plugs into the charging port and provides an ordinary household socket there. The inverter sits in the car; apart from the adapter, nothing else is needed.

Depending on the model, the output is in the order of a household socket. That is enough for tools on a building site without power, a kettle at the campsite, an e-bike charger or, in an emergency, a fridge and some light. The car stops supplying at a minimum charge level so you can still drive afterwards; on many models you can set that limit in the menu.

One limit is not negotiable: a V2L socket must never be connected to the house wiring, not even through a lead into a wall socket. Feeding into the house without separation from the grid endangers people working on the lines and is not permitted. If you want to power the house from the car, you need V2H, and with it a different installation.

On a used car the adapter is part of the equipment and is often missing. Equipment lists in listings are frequently incomplete; ask the seller about it explicitly and have them show you the adapter at the viewing. It can usually be bought again, though not always cheaply.

For V2H, power from the battery has to reach the house wiring in a way that complies with the rules for generators. Usually that happens through a bidirectional DC wallbox with its own inverter. Some cars can also feed back through the AC connection; the inverter then sits in the car. Which variant your car supports is not in the brochure but in the list of chargers the manufacturer approves for it.

On top comes an energy management system that decides when the car charges and when it supplies, and that never lets the battery drop below the level you need for your next trip. With solar panels the obvious use follows: solar power into the car by day, from the car into the house in the evening. Without your own generation, V2H mainly pays with a tariff where electricity costs different amounts at different times.

If the house is to keep running in a power cut, you need a device that disconnects it from the grid before the car feeds in, and a charger that supports this island mode. Not every V2H system can do that; some only supply while the grid is up. If backup power matters to you, that is the first question for the supplier.

A V2H system is a generating unit at the house connection. A qualified electrician installs it, and it is registered with or approved by the grid operator; the rules are in the operator's technical connection conditions. That takes time, and this is often where projects run longer than planned.

With V2G the car supplies power to the public grid under outside control. An electricity supplier or aggregator pools many cars, uses them when the grid needs energy or power is expensive, and charges them when it is cheap. The owner decides how much of the battery may be used for this and when the car must be full.

That takes more than technology: meters that record consumption and feed-in separately over time, a tariff that pays for what you feed in, and rules on grid fees and levies that do not charge the same electricity twice, once when charging and once when supplying. These rules are a matter for each country and are being revised in many places. The national energy regulator and the local grid operator are responsible.

In 2026 V2G has only begun to reach everyday life. In a few countries there are now offers in which a carmaker and an electricity supplier sell car, bidirectional wallbox and tariff together; elsewhere it runs in pilot projects or not at all. If you buy a car for V2G, you are buying a possibility, not an income. Check whether there is a concrete offer for your model, in your country and with your grid operator before you count on it.

Technically, V2G depends on communication between car and charger. The older CHAdeMO system supported both directions early on. With CCS, the standard common in Europe, it takes a newer version of the communication standard, ISO 15118-20, which car and charger must both support. Whether a car gets it through a software update is up to the manufacturer.

Every kilowatt-hour the car gives out, it must have charged first. The battery therefore goes through extra cycles, and cycles contribute to ageing. How much depends on how they are run. Shallow cycles in the middle of the charge range at low power are far gentler on a lithium-ion cell than fast charging from nearly empty to full, and the currents in V2H and V2G are small relative to the size of the battery.

Then there is calendar ageing, which depends on charge level and temperature. A well-configured energy management system can even help if it keeps the battery from sitting full. A badly configured one does harm if it keeps the car charged high to hold a reserve for the house. How large the effect is over the years cannot be put in a general figure; solid statements exist only for specific cell chemistries and operating patterns.

What matters is what the manufacturer commits to. Some allow bidirectional use only with approved equipment and cap the energy supplied or the operating hours within which the battery warranty is unaffected. Others say nothing about it in the warranty terms, and silence is no commitment in a dispute. Read the terms before you buy a system, not once the battery starts to fade.

Every detour also costs energy. In both charging and supplying, some is lost as heat in the inverter and the battery; a kilowatt-hour that goes into the car and later comes back into the house does not arrive in full. Whether the round trip pays depends on the price gap between the electricity you store and the electricity it replaces.

The first question is one you ask yourself: how often is the car plugged in at home at the times when the house or the grid needs the power? A car that is still in the office car park in the evening does not cook dinner. V2H and V2G pay off where the car is connected for long and reliable stretches.

“Bidirectional charging” on its own says little until it is clear which level is meant and with which equipment. Settle the remaining points before you buy, with the dealer for a new car, and with the data sheet, owner's manual and manufacturer for a used one: