The idea
An electric vehicle is a large battery on wheels. Most of the time it is parked. Bidirectional charging lets that battery not only take energy but give it back - to a home (vehicle-to-home, V2H) or to the grid (vehicle-to-grid, V2G). One EV with a 60-100 kWh pack can hold several times the energy a typical home uses in a day, turning parked fleets into flexible grid assets.
V2H versus V2G versus V2L
V2L (vehicle-to-load) powers tools and appliances from the car's socket, usually a few kilowatts, and is common today. V2H powers a whole home, typically 7-12 kW, providing backup and load shifting. V2G exports to the grid through an approved charger and aggregator, earning capacity and flexibility payments. Each step adds power, complexity and regulation.
Hardware and standards
V2H and V2G need a bidirectional charger and a vehicle that exposes its battery control over the connector. On the DC side, CCS (and now NACS) can carry bidirectional power where the car supports it. The key standard is ISO 15118, whose Part 20 defines bidirectional charging, and the CHAdeMO protocol pioneered DC V2G in Japan. AC V2G is emerging in Europe. Wallbox's Quasar 2, rated at up to 12.8 kW DC, is one of the first CCS bidirectional chargers available to consumers.
What V2H delivers
A vehicle-to-home setup can power a house for up to three days (based on about 25 kWh daily use) during an outage, and can shift cheap or solar energy into expensive peak hours. Suppliers claim savings up to about $1,500 a year where time-of-use tariffs are steep. The catch is that a home needs a transfer switch or "power recovery unit" to isolate from the grid during backup.
What V2G delivers
V2G value comes from grid services: capacity, frequency regulation, demand response and peak shaving - not from raw energy arbitrage. Nuvve's GIVe platform aggregates bidirectional chargers and fleet EVs, dispatching power for revenue. School buses and depot fleets are ideal because they are parked predictably and in numbers. Regulators in several European markets and US states now allow V2G, but rules vary widely.
Does it harm the battery?
Fears of accelerated degradation are overstated if dispatch is managed. Bidirectional charging delivers a steady, controlled power flow, quite different from the frequent high-power demands of fast DC charging or hard acceleration. Wallbox notes that managed V2G is potentially less wearing than driving. Aggregators typically cap throughput and cycle depth to protect warranty terms.
Economics and barriers
Today V2H pays back through backup value and tariff arbitrage; V2G revenue is real but modest and region-dependent. Barriers include limited vehicle support, charger cost, utility approval, standards maturation and the need for an aggregator. The direction of travel is clear: as ISO 15118-20 adoption spreads and more EVs enable bidirectional power, V2G/V2H will shift from pilot to product.
Bottom line
Bidirectional charging turns parked EVs into storage and grid assets. It is technically proven, increasingly standardised and economically emerging. For fleets with predictable duty cycles, V2G is the more compelling near-term case; for households, V2H backup and solar self-consumption are the draw.