Island Mode and Anti-Islanding

Last modified: Aug 02, 2026

Island mode and anti-islanding describe two related but distinct aspects of operating safely when the utility grid is unavailable.

What island mode means

Island mode is intentional operation of a local electrical system while it is disconnected from the wider utility grid. A compatible EV and bidirectional charger may help energize selected home or building circuits during an outage, but the installation needs equipment that safely separates the local system from the grid and controls voltage, frequency, protection, and available power.

Not every vehicle-to-home or vehicle-to-building system can operate as an island. Some bidirectional systems work only while a stable grid connection is present, and backup operation may require a transfer device, gateway, stationary equipment, or specific installation approval.

What anti-islanding means

Anti-islanding is the protection function that prevents a distributed energy source from unintentionally continuing to energize a grid section after the utility supply has been lost. This protects workers and equipment and supports controlled reconnection.

Anti-islanding does not mean that backup power is impossible. An approved system can first isolate a defined local circuit and then form an intentional island under controlled conditions. Requirements depend on the electrical installation and applicable grid-interconnection rules. IEEE work on intentional islands and UL guidance on bidirectional charging illustrate why the operating boundary and protection scheme must be considered together. IEEE P1547.4: Intentional islands UL Solutions: Bidirectional charging safety

See Bidirectional charging for the wider category of reversible EV energy flow.

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