V2L is intended to supply a single load directly from the car. It was designed for this purpose and this usage is safe.
To attempt to run your entire house off the car is ill-advised in several ways:
- You cannot convert an IT supply into a TN-S network simply by grounding. About the only safe way to do this would be to galvanically separate the two with a transformer (or a separate rectifier/inverter, but that increases losses way too much)
- And that's not even taking into account houses with 3-phase supply.
- You have to ensure to never connect the car and the grid in any way. A single mistake can lead to danger to human life and damage/destroy involved devices (i.e. the car and all infrastructure in your house).
- In turn, this means every time you want to switch between car and grid, everything will be unpowered for a second or longer. Aside from the inconvenience of losing clocks and settings all the time, this will shorten the lifespan of electronic devices exposed to those short outages regularly.
- Again, all this is way out of the design specifications for the car. Solar inverters and switches that allow for gridless and grid-connected operation are expensive because they were designed to do this safely and reliably.
Would I use this in a emergency (prolonged power outage) to connect some essential loads like a freezer, heater etc while they are disconnected from the house network? Absolutely, with the knowledge that running more than one load is a calculated risk I would be willing to take, because of emergency. Would I connect it to my entire house as a power storage? You couldn't pay me to do that.