Overview
Vehicle-to-grid (V2G) and vehicle-to-home (V2H) use bidirectional chargers to move energy out of the electric vehicle battery as well as into it. V2H supplies a building's loads during peak tariff periods or a grid outage; V2G aggregates many vehicles through an aggregator to provide grid services such as peak shaving, frequency response and local congestion relief. The charger requires a bidirectional power stage, an isolation stage, and in most markets a certified interface to the distribution network operator.
How it works
A bidirectional charger contains an AC/DC stage and a DC/DC stage with active isolation, allowing power flow in both directions on either the AC (CCS) or DC (CHAdeMO/CCS DC) path. An aggregator platform receives grid signals such as frequency or a demand-response dispatch and translates them into charge or discharge setpoints for each vehicle, subject to user preferences, state of charge limits and battery warranty terms. Chinese modules such as the Sinexcel BAC300100-II deliver 15-20 kW of bidirectional conversion with up to 98% peak efficiency in the isolated DC/DC stage.
Advantages
- New revenue stream for vehicle owners and fleet operators
- Grid-scale flexibility without building dedicated storage assets
- Cuts building energy costs through V2H peak avoidance
- Improves resilience: vehicles can back up a home or depot
- Supports distribution network and avoids local upgrades
- Compatible with reserve and frequency-response markets
Considerations
- Bidirectional chargers cost considerably more than unidirectional units
- Limited vehicle models currently support true bidirectional DC operation
- Battery degradation concerns and warranty exclusions
- Regulatory and grid-connection approval still fragmented by country
- Aggregation and settlement processes are immature
- Standards for CCS-based V2G continue to evolve
Applications
- Home energy management with V2H
- Fleet depots with long dwell times
- Workplace charging with vehicle aggregation
- Virtual power plant participation
- Grid congestion relief in constrained areas
- Emergency backup for homes and critical loads
Cost breakdown
Bidirectional chargers typically cost 2-3 times a comparable unidirectional unit because of the added isolation and bidirectional power stage. In China, module-level pricing for 15-20 kW bidirectional V2G converters has fallen to levels comparable with unidirectional DC modules, and 7.4-19.2 kW bidirectional AC wallboxes are now offered at consumer price points in the low thousands of USD.
Market outlook
V2G remains the smallest but most strategically significant sub-segment of the EV-charging value chain. Vehicle-side support is the binding constraint: genuine bidirectional DC capability is still limited to a minority of models, and standards work on CCS-based V2G continues. Industry consensus is that V2H will commercialise first in residential markets, while V2G scales once aggregator frameworks and market rules mature.