Farmers, construction, etc are required to keep their non-taxed vehicles off the road, if they're caught on the road with them they can be required to pay any t

Farmers, construction, etc are required to keep their non-taxed vehicles off the road, if they're caught on the road with them they can be required to pay any taxes on the entirety of the odometer since the last sale. The cross-state-borders could simply require you to report your odometer readings on exit and entry to the state. I don't think it's unreasonable to say that the majority of drivers would not care about a few dollars "extra" from some cross-state adventures, and those that do care can do the extra couple of minutes of working. Another alternative would be to require all car chargers (including those connected to personal solar) include meters internally and require the owners to pay taxes on those (which would be trivially integrated with pricing on commercial chargers, but there are plenty of non-commercial deployments).