You might think an electric car is a car, but you’d be wrong. It is a giant battery that, for some reason, spends most of its existence powering a thing that’s not moving at all. That’s why Nissan sees a future for the Leaf as a battery that can power your house.

The concept, called “Vehicle-to-Home” electric supply or bi-directional charging, has been available in Japan but will soon be rolling out to Australia, , after regulatory testing.

The idea of a home battery is not especially new. Energy usage is uneven, which strains service providers during peak periods. Plus, the times when a green energy grid produces lots of energy is not necessarily the same time as people use lots of energy, meaning a lot of that green energy goes to waste. Without a way to store that energy for later, solar and wind can only get us so far.

As battery costs have steadily fallen, large home batteries are an increasingly tenable solution. But they’re still expensive, costing thousands of dollars or more to buy and install. Tesla’s Powerwall, for example, .

That’s where the Leaf comes in. From The Driven:

As Tim Washington, CEO of charging solutions provider Jetcharge put it when speaking at the event, “Cars will be an energy asset first, and a mobility asset second.”

“What I mean by that is you are going to use your cars probably more as batteries than as vehicles.

“As we know vehicles are parked 90% of the time – that is one of the criticism levelled at cars. But what if they are the most efficient asset that you have because it’s doing work even when its parked?”

Nissan’s global head of electric vehicles, Nic Thomas, went on to offer some not-so-subtle shade at Tesla for the , calling them “a complete waste of resources,” because most of those customers will also have an electric car, which as we have discussed is not a car but a battery spending most of its existence parked in the driveway.

And it’s not just a battery, but a big, carefully engineered battery. Here in the U.S., , or a little under 30 kWh per day.

The Leaf comes in : 40 kWh that provides approximately 150 miles of range and a 62 kWh battery with 226 miles of range. So even a partially-charged smaller Leaf battery could power many American homes for several hours. And in the event of a power outage, a fully-charged Leaf could power the average American home for more than two days.

Of course, most people wouldn’t want to use their Leaf to power their house for days. In the rare event people will want to use their electric car as something other than a battery, it will require a charge. On Nissan’s website explaining , the company says it charges the Leaf during the night when energy demand is lower, so the car is fully charged in the morning. But, using the Leaf as an energy source will mean it might not be fully charged when you go to use it in the middle of the afternoon.

And you know what? That’s fine! , and most are under six miles. Even if your house drains your Leaf battery by 50 percent (which would be extreme) you will still have 75 miles of range, enough to run a bunch of errands and pick the kids up from school.

With the constant consternation over and whether or not , it’s nice to see at least one automaker thinking about how to put cars to good use when they’re not being driven, especially an environmentally friendly one. It’s also a solid business proposition for the environmentally conscious, since you won’t have to spring for a home battery.

There are currently for bi-directional charging in Franklin, Tennessee and Hagen, Germany for Leaf fleets, but it’s not clear when this feature will be available to households outside of Japan and Australia. A spokesman for Nissan told Jalopnik, “We’re currently looking at ways to bring this technology to market in the US but have nothing to announce at this time.”