I would guess that you could run the PHV on the ICE only. what if you didn't have electricity for a week (act of nature) but still had to run errands? this is the downfall of all electric vehicles and having it as your only driver, you could be screwed if you don't have electrical to plug in your car.
that's exactly right. when you run out of plug in juice, it's the same as our pri. you can drive forever as long as you can find a gas station. of course, you're dragging around a bit of extra battery weight.
And on that note - despite the heavier weight, it will still get better MPG than a stock Prius - even when you don't plug it in.
Without plugging-in, the two EV sub-packs are disconnected from system and stay in "fully depleted" condition (i.e. the minimum SOC allowable by Toyota). In long time, they will slowly discharge further to below the minimum. I wonder if this may deteriorate the batteries capacity and service life? In the final product Toyota may recommend minimum plugging-in strategy.
The PHV Li batteries (3 of them) are heavier then the one Nickel battery in the regular Gen 3. The PHV HV battery has about one third more energy capacity than the Gen 3 HV battery (1.73 kWh versus 1.3 kWh), so it can regen more. It probably also gives longer EV range and speed (in HV mode). These are, to my opinion, the main factors in in achieving the slightly better milage in HV mode.
