Island Mode / Islanding

Island mode (also called islanding) is when a solar-plus-battery system disconnects from the utility grid and operates independently as a self-contained power source. The home becomes an “island” — generating, storing, and consuming its own electricity without any connection to the grid.

Islanding is what happens automatically when a grid outage is detected in a system with battery backup. The transfer switch disconnects the home from the grid (to prevent backfeeding electricity to utility workers), and the battery and solar panels take over powering the home. During island mode, the inverter must carefully manage power flow — balancing solar production, battery charge/discharge, and household demand in real time. The system continues operating in island mode until grid power is restored, at which point it automatically reconnects. Intentional islanding is the desired behavior during outages. However, unintentional islanding (where a solar system continues feeding the grid during an outage) is a safety hazard — which is why anti-islanding protection is required by code in all grid-tied inverters. Modern hybrid inverters and battery systems handle the transition to island mode seamlessly, often in under a second.