There’s a parked battery in a lot of American driveways that’s five to ten times larger than the wall-mounted home battery next to the garage. A typical EV holds 60 to 100 kilowatt-hours — enough, on paper, to run an average house for two or three days. The question isn’t whether the energy is there. It’s how to get it into the panel safely.
Vehicle-to-home, or V2H, is the ability to pull energy out of an EV’s battery and use it to power a building, not just push energy into the car. It turns a vehicle from a load into a backup source — but only if the rest of the system knows how to handle the handoff.
A battery on wheels
The scale is striking. The average U.S. household uses roughly 10,500 kilowatt-hours a year, according to the U.S. Energy Information Administration — about 30 a day. A mid-size EV pack can cover several days of that and far longer if you’re only backing up essentials. As driveways fill with electric cars, that’s an enormous amount of idle storage sitting unused during exactly the outages people fear most.
That math is why automakers and utilities are paying attention. A neighborhood of bidirectional EVs amounts to a distributed fleet of home batteries that already exists and spends most of its life parked — capacity that could ride out a storm, or even feed the grid at peak, if the hardware on both ends is ready for it.
But the switch still matters
Here’s the part that spec sheets gloss over: an EV can’t simply energize a house on its own. Sending power from a car into home circuits during an outage demands the same safety logic as any other backup source — the home has to disconnect from the grid first, so the car’s energy can’t flow back onto utility lines. That’s the transfer-switch function again, just with a different battery behind it. It also takes a charger built to run in both directions; most EV charging is one-way, and pulling energy back out needs hardware made for it.
The vehicle-to-home backup capability in Sigenergy’s 25 kW bidirectional DC charger is designed to work with the system’s islanding and load control, so the car can carry the house through an outage without anyone rewiring anything — the switching, not the car, is what makes it safe.
Worth waiting for?
V2H is still early, and not every EV supports discharging yet. But for households planning years ahead — especially those adding solar and storage now — choosing equipment that already speaks V2H keeps the door open to turning the car in the driveway into the largest backup battery on the property.
If a future EV is part of the plan, it’s worth checking that the charging hardware can run in both directions before locking in a one-way setup.
