Vehicle-to-Grid (V2G): Homes Get Power From Electric Vehicles

Electric cars have huge lithium ion batteries that store a large amount of energy. But for a large majority of the day and night, the electric car and it’s battery just sit idle. Car manufacturers for Toyota and Nissan are starting to think about how to tap into that battery, both for use at home and as a resource for the power grid.

The latest advance is a home charging station from the Japanese company Nichicon. It’s the first commercially available charger for the Nissan Leaf that allows power to flow in two directions. The house can power the car and the car can power the house. When the house is powering the car, it’s not the house per se, but the home’s connection to the power grid. Usually such charging happens during the evening hours, when the car is parked in the garage and when demand for electricity is lower and cheaper.

During the day, the Nichicon charger could be set by the owner to make the car’s battery available to the power grid, which would draw electricity from the battery in order to meet demand during power peaks. The owner would get some kind of rebate, which would lower the cost of electricity for the house. But such a system could also work to make renewable energy, such as wind power and solar energy, which are intermittent, more reliable forms of energy. Power from those sources, for example, could be "stored" on electric car batteries and pulled during peak demand.

The power from the car’s battery can also go to the home. This could be useful during an emergency situation, such as a power outage. Nissan says the batteries in its power station units hold about 24 kilowatt-hours, or enough to power even the most energy-hungry appliances in a home (air conditioner, stove, refrigerator, washing machine and dryer) at the same time for about a day, if they are at the lower end of the consumption range.

Inductive Chargers Juice Up Electric Vehicles

Toyota has its own system that works via a 100-volt AC inverter on a Prius plug-in hybrid. That converts the electricity in the car battery to AC, which can be used for home use. The flow of current is controlled by a communication system linked between the car, the house, and a charging stand.

With a full tank of gas and fully charged battery, a Prius can supply an average Japanese household about 10 kilowatt-hours for about four days (one is essentially using the Prius as a generator), Toyota reports.

Both of these systems are being rolled out in Japan first. That’s because the best return on investment for homeowners will be in places where the cost of electricity is high and there are power outages. The loss of much of its nuclear power over the coming years could mean electricity shortfalls, so Japan fits that pattern better than the United States. That doesn’t mean it will never make sense for Americans, though – California, for instance, has high electricity costs, and more homes there are using solar power and wind energy.