If you're going any real distance, the beginning charge level really doesn't matter. We left home last month with zero charge (SNAFU), and got a reported 11% (+/- 120 mile) fuel-free miles out of 1,100 miles with several 6-7,000 foot passes with no chance to top off the electrons. Even so, we got 38 MPG reported.
On the way back we started with a full charge, and got a little less overall MPG and about the same fuel-free mile percentage. Both directions on this trip here in the western US have a majority of 80 MPH speed limits... That helped make an 1,100 mile 17 hour single day, single driver "cannonball run" on the return trip a reality. I will say that I really enjoyed that seat time in the etron. I would not have made it in the competition I believe after having driven them on test drives before we bought the etron.
BTW, has anyone else noted that the "Driving" lights function that turns on both (2016) cornering lights doesn't work above 70 MPH? I was composing a service ticket in my mind for several hours until I figured this out! At least they stay on when you hit real speeds.
In my opinion, when you can only leave home with a reported 22'ish mile electric range, the initial charge level just doesn't matter if you're on more than, say, a 75 mile trip. The pre-loaded electric kWh vs gasoline BTU benefits diminish rapidly with distance. It then comes down to driving style and your ability to manage the regeneration on braking and downhills, your particular acceleration aggressiveness, your willingness to bleed off speed when approaching a hill crest, and your being in tune with the black magic surrounding the optimal use of the EV vs other modes in varying driving conditions.