V2G can be done in two ways:
- 1: As a way to eliminate/solve power shortage in a working grid
- 2: As a way to eliminate generators in case of a power outage (grid is down/blackout)
Option 1: The first option is relatively simple, but is also not as useful for a regular car owner. It solves someone else his problem (the power company's problem). There are other solutions to solve power shortages that are more feasible, such as stop charging EVs. In The Netherlands there is a system/app that can do this: Jedlix. What is does it stops/starts charging your EV in 15 minute intervals depending on power shortage. This should, when enough cars participate, eliminate the need to boot up natural gas power stations. This is pretty much as effective as backfeeding your Tesla's power in the grid:
Instead of feeding your power back to the grid that is used to power a car a mile further down the road, you can just stop charging cars. That lowers the total grid usage.
So I do not believe Nissan's solution (which does actually backfeed power in the grid) is of very much use. There is no use in draining the batteries from 100 cars to feed the grid, when there are 100 cars elsewhere charging if you could also simply stop the charging process of those 100 cars. The net result is the same.
The "stop charging" solution is something that could be done tomorrow if Tesla would implement this in firmware and cooperate with power companies, such as the Jedlix app already does today.
There are significant losses in convertering AC to DC and vice versa, generated heat from the converters, etc. From an environmental standpoint the "stop charging solution" is much better than "drain car 1 to charge car 2 and a power vacuum cleaner".
Option 2: The second option is much more complex. You would need to sever your home infrastructure from the grid in order to let the car power your house, otherwise your car would be trying to power the entire neighborhood and that won't work. So there needs to be infrastructure in your home to accomplish this, some kind of ATS/STS (Automatic Transfer Switch, Static Transfer Switch) with two inputs, 1 from the grid and 1 from the car.
Any charging device such as the HPWC or a third party charger would need to be able to cope with backfeeding and also the required amount of power (which can be significant). It would also require some sort of converter to convert DC back to AC.
So this won't work without some major modifications to both your electrical installation at home, the car and the charging system in your home.