Electric vehicles (EVs) can do more than simply transport people or goods from place to place. Through smart charging and bidirectional charging, their batteries can become an important societal resource. 

When these EV batteries are charged matters. Smart charging — loading electricity into a battery when renewable production is high but demand is low — supports a more efficient energy system. A special category of smart charging is bidirectional charging, which enables EV batteries to serve as mobile power sources. Bidirectional charging allows EVs to feed electricity back into the grid (vehicle-to-grid, or V2G) during peak hours or other times of need. 

If utilised to its fullest potential, bidirectional charging can be of benefit to both the individual vehicle user and the energy system as a whole. It enables EVs to act as a distributed energy system, eliminating the need for additional storage within an electricity network. When coupled with smart charging, bidirectional charging increases the use of energy from renewable sources, even at times of low production. If there is high demand, EV batteries can be used as an energy source, including during a power outage, and feed electricity into a building or the grid.

To realise the potential of bidirectional charging, however, it is important to have the right policy framework. In this brief, we propose three principles to help realise the benefits of bidirectional charging for all.