There is another consideration and that is what other "useful" things can you do while charging. If you define "efficiency" as simply speed of charge, then getting SoC down to 10% and charging only enough to get you to the next available DCFC with 10% remaining (the "A Better Route Planner" algorithm) is best. From here in WV, ALL long-distance trips start with a long (150 - 220 mile) trip to the first DCFC. Some trip routes simply cannot be made without AC Level 2 charging, often an overnight stop. On our most recent trip north to Toledo, OH, we never spent one minute "waiting" for charging. The first leg was to Easton Gateway in Columbus, OH (170 miles). Eating and a little shopping (what they hope you will do in exchange for the free DCFC electrons) filled the entire 1 hr. 15 min. charging time. On to Toledo, we attended our Friday evening function, then charged {for free; with pre-arrangement} overnight at a Ford dealership within walking distance of our motel. Saturday saw some driving to the (wonderful!) Toledo Art Museum, lunch, and our Saturday evening function. Back at the motel, we AC Level 1 charged {free} overnight at an outdoor outlet (with permission). Sunday took us from Toledo to the Tanger outlet mall near Columbus for a 2 hour shopping/snack spree {with free AC Level 2 charging}. We then traveled on to Lancaster, OH where we visited their brand new DC Level 2 DCFC. We plugged in only long enough (50 minutes) to eat supper, then got back on the road. This was the only charge for which we paid, $15.64 for 32.004 kWh. Continuing home with no anxiety, we had simply worked charging into other needed activities (eating, sleeping, shopping) with NO minutes waiting to get enough charge to proceed. I am sure that many others apply these same principles.
