In a power cut, vehicle-to-home (V2H) works by disconnecting your home from the grid and letting the car become the supply. A gateway opens the grid connection, the bidirectional charger stops following the grid and starts forming its own — setting the voltage and frequency your circuits run on — and power flows to a limited set of home circuits until the grid returns and the system reconnects.
Key Takeaways
- V2H is a mode change: the charger stops following the grid and forms a local supply instead.
- Isolation comes first — the gateway cuts the street connection before any backup power flows.
- Backup is capped by the charger’s rating, so it covers chosen circuits, not the whole house.
- When the grid returns, the system synchronises and reconnects on its own.
Two Modes: Following the Grid, Then Forming It
Normally, a bidirectional charger is grid-following. It watches the grid’s voltage and frequency and matches them, whether it is charging the car or feeding power out. That works only while the grid is alive to follow.
An outage removes the reference. The charger then has to switch to grid-forming: it creates a stable local supply on its own and holds the voltage and frequency steady as your lights, fridge and other loads switch on and off. This is the step ordinary equipment cannot do — a one-way charger only follows, and a solar inverter without island capability simply shuts down. It is also why V2H works only as a matched, approved system of car, charger and gateway, as our overview of bidirectional charging: V2L, V2H and V2G explained sets out.
The Switchover, Moment by Moment
| Moment | What happens |
|---|---|
| The grid fails | The gateway detects the failure and opens the connection to the street supply. This isolation — anti-islanding — guarantees your car never energises lines that repair crews are working on. |
| The charger changes role | It stops charging, reverses, and begins forming the island supply from the car’s battery. |
| Backup circuits come live | Power reaches the circuits wired for backup. Everything else stays off, by design. |
| The island runs | The charger holds the local supply steady and discharges the car down to the floor level you set, keeping charge in reserve for driving. |
| The grid returns | The gateway waits until the street supply is stable, synchronises the island back to it, then closes the connection. The car returns to charging. |
Expect a short gap between the grid failing and backup power starting — the system has to detect, isolate and switch first. How long the gap is depends on the equipment, so check the maker’s specification; clocks, routers and other electronics may restart during it.
While the Island Runs
- The output has a ceiling. The charger can only supply up to its rated output, which is why backup covers chosen circuits — lights, refrigeration, communications, a few outlets — rather than the whole house. Heavy loads such as central air conditioning or an electric range stay off.
- Rooftop solar usually pauses too. A standard solar inverter is also grid-following, so it stops in a cut unless the system was specifically designed to work in island mode. Do not assume your panels keep generating.
- The floor protects your driving. Discharge stops at the battery level you set, so an outage cannot strand the car. How long backup lasts depends on that setting and what you run — the system displays its own estimate.
What You Use Every Other Day
The gateway and bidirectional unit only earn their keep during cuts; the rest of the time the car simply charges. If your car is not yet V2H-capable — most are not, as when vehicle-to-home will be available explains — a one-way unit such as the EVDANCE EV-ACT5006T 48A Level 2 wall charger covers daily charging; see the residential charging solutions page for the home range. A one-way charger cannot be converted to V2H later.
Frequently Asked Questions
Why can’t the car just plug straight into the house?
Because the house must be isolated from the grid first. Feeding a home through a plug or homemade cable — backfeeding — can energise street lines and endanger repair crews. The gateway’s isolation is what makes V2H safe and legal; it is licensed-electrician work.
Do I have to switch anything when the power goes out?
No. Once the system is installed and your settings are in place, detection, isolation and switchover are automatic. Your job is only to keep heavy loads off the backup circuits.
Can V2H run my whole house?
No. The charger’s output rating caps what it can supply, so backup is planned around essential circuits chosen in advance. Whole-house supply would take a much larger fixed system.
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?
