Anti-islanding is the protection that stops a discharging electric car — or any home generator of power — from feeding electricity into the local grid lines when the grid has gone down. The moment a bidirectional system senses the outage, it must cut its connection to the street, so the only thing it powers is your own isolated home circuits. It is the reason vehicle-to-home only works through matched equipment with proper transfer gear, and never through an improvised cable.
Key Takeaways
- Anti-islanding stops a discharging car from energising grid lines during an outage, protecting repair crews and equipment.
- It works as a chain: sense the failure, disconnect from the street, isolate the home’s circuits, then supply them locally.
- Backfeeding through an improvised cable is exactly what the rule forbids — V2H needs matched equipment and transfer gear.
- One-way chargers never export, so they sit outside this rule entirely.
The Hazard: A “Dead” Grid That Is Not Dead
When power fails, the utility isolates the fault and sends out repair crews, who work on lines they reasonably believe are dead. If a house quietly pushes power backwards through its meter at that moment, those lines become live again — an “island” of power in a sea of outage. That can injure lineworkers, and it can also damage equipment when the island’s power runs out of step with the returning grid supply. Anti-islanding exists to make sure the island never forms: our overview of bidirectional charging: V2L, V2H and V2G explained sets out the systems this protection sits inside.
How Anti-Islanding Works
The protection is a chain, not a single switch:
- Sense. The bidirectional charger continuously watches the grid connection for the voltage and rhythm of a healthy supply.
- Disconnect. When that healthy signal disappears, export stops and the grid side is cut off — automatically, in moments, with no decision left to the homeowner.
- Isolate and supply. Transfer equipment separates the home’s chosen backup circuits from the street, and only then does the car feed those circuits as a private, local supply.
- Reconnect safely. When the grid returns and stays stable, the system can reconnect in the proper order rather than simply merging two live supplies.
| Situation | What the system does |
|---|---|
| Grid healthy | The car may charge, or export where a programme allows it, in step with the grid |
| Grid fails | Export stops; the street connection is cut before the home backup circuits are fed |
| Outage continues | The car powers only the home’s isolated backup circuits — an intentional, local island |
| Grid returns | The system reconnects in sequence once the supply is stable |
Why There Is No Improvised Version
This protection is also the answer to a tempting question: in an outage, why not just run a cable from the car into a household socket? Because backfeeding a house that way skips every link in the chain above — no sensing, no disconnection, no isolation — and creates exactly the island the rule forbids. It is unsafe and it is not how vehicle-to-home is permitted to work. Genuine V2H uses a bidirectional charger matched to the car, transfer equipment installed for the purpose, and in many places utility approval for anything that can export. Availability is still limited to specific cars and systems, as our status check on when vehicle-to-home will be available shows.
What It Means When You Shop
Anti-islanding is invisible when it works, which is the point. For a buyer, its practical effects are the shortlist itself: the cars offering home discharge are listed in which EVs can do bidirectional charging, the home equipment is a matched unit rather than a standard wallbox, and the system costs more than plain charging — part of the maths in is bidirectional charging worth it.
Everyday charging is a separate, simpler job. EVDANCE chargers are one-way units: a wall charger such as the EV-ACT5006T 48A Level 2 wall charger charges the car and cannot discharge it, whichever backup route you add later. Our residential charging page covers that everyday range.
Frequently Asked Questions
Does anti-islanding apply to solar panels too?
Yes — the same duty falls on rooftop solar inverters and home batteries. Anything that can generate power in a home must stop exporting the moment the grid fails, and only feed isolated circuits through proper equipment. The EV is simply the newest generator on the list.
Can anti-islanding be switched off so my car powers more of the house?
No. It is a built-in safety function of certified equipment, not a setting. What can be chosen at installation is which circuits the transfer equipment feeds — the protection itself is not optional.
Does a normal home charger need anti-islanding?
No. A one-way charger never sends power towards the grid, so there is nothing to island. The requirement arrives only when equipment can discharge — a bidirectional car-and-charger system, a home battery or solar.
Related Reading
- Bidirectional Charging Explained: V2L, V2H and V2G
- When Will Vehicle-to-Home Be Available?
- Which EVs Can Do Bidirectional Charging?
- Is Bidirectional Charging Worth It?
