Umm thou this is getting a little off topic. The Volt only provides about 60% of its true capacity because you risk damaging the battery if you charge a lithium up to its maxiumum charge and down to its minimal charge. I know this trick works because my Sony laptop is able to hold the battery charge at 50% and after 5 years of use the battery shows almost no degradation. GM I think decided to go conservative as well and I have noticed the range estimator seems a bit conservative in most situations. The amount of usable power it shows left however is accurate.
Still there's no such thing as no range anxiety on an EV. It's like going to space on a tank of air. Unless you have some way to produce large amounts of it or there's so much it's ridiculous, there will always be some range anxiety.