DaveSmith Do any cars actually offer V2H ? Some come with a 240V inverter which lets you plug in indivuidual devices when you're out camping, for example.
The venerable Nissan Leaf does offer full bidirectional access to its battery via the Chademo interface, and there are some V2x chargers for those. It does seem like a rather obvious proposition that you'd be able to plug in such a device to your existing inverter, as a battery-like device.
However, Chademo lost out to CCS in Europe, so I can't really see anyone wanting to invest in new hardware for an obsolete interface. There's lots of talk about "bidirectional charging", but I'm not sure if anything's been standardised yet.
I think the upcoming Renault 5 will have V2x, but I think I heard that the car will output AC directly, rather than just giving DC access to the battery.