There has to be something more going on. In the scenario I described, I'm coasting downhill which provides regen—not using any amount of accelerator so no power draw. Yet, the battery range and HV range both decrement.That could simply be the result of the engine running at idle speed -- it's generating some power, but not enough to fully power the car, so the rest is coming from the battery so EV range depletes also (but probably at a slightly lower rate than it would have). That's because the computer is only keeping the engine running to warm it up -- when needed to actually generate enough to drive the car, it's running at higher RPM.