I've drove Chevy volts. the instant torque is nice i will give you that but for the additional money you have to spend and low range I'll pass. 200/300 miles might seem decent but then you can't just pull into your local petrol station and fill up and continue onGod, I know. I drove a Tesla once, and I had to put up with all that torque at any RPM, instantly. Just awful!
It depends on how you drive, just like any car, but between 200 and 300 miles, generally.
Seriously, drive one. It's a completely different experience from what you're used to, in a good way.