Re: I've been pointing this out for years.
"Yes, but 61% of road fuel price is tax + duty. No government is going to give up on that, whether you get your power from the grid or home PV. Electric cars are only significatly cheaper to "fuel" because they aren't a big enough market yet."
There will come a time when you will have to report your mileage and the road tax will be based on that. I expect that the car may do it automatically "for you" and you will be billed periodically.