I'm looking at the Supercharger map. For a drive from Seattle to Portland and back again, it seems like my most efficient plan would be to stop in Centralia, charge fully to 100%, then drive to Portland and back to Centralia to charge assuming I only want to use Superchargers? I don't see any better options if I don't want to drive out of my way to Woodburn or Sandy, OR just to charge.
It's a good thing Tesla is committing to adding urban SC's in 2018 because this kind of trip is really inconvenient with SC's only in between cities and away from cities.