The electric car owners are not thr ones paying the externalities for it either. You can make the case the externalities are smaller but they still exist.
If we do need to triple the grid's copper, that would indeed result in unpaid externalities because of poor mining practices.
Hopefully, the grid doesn't need to triple because of local storage. If it does, hopefully, the recyleability of copper makes the one time cost of mining and refining a smaller externality.
The electric car owners are not thr ones paying the externalities for it either. You can make the case the externalities are smaller but they still exist.