GM is planning to release the Chevy Volt in November 2010. Put simply, the Volt is a battery electric car with a built in generator. It can drive up to 40 miles per charge on just the batteries and then the generator kicks in. Like a conventional gas car, you can drive until the tank is empty and you can refill at any gas station and keep going as far as you like. Unlike a conventional car though, you can also plug it in, charge it up and then start driving from battery power again.
Note that these wild expectations don't even need to be from the company in question. The expectation could be set by the media or word-of-mouth. GM is saying 40 miles all electric and 230 MPG, there is a large portion of the population that are going to take this at face-value and expect it when this car hits the streets.
- you have a lead foot - fast acceleration eats watt-hours
- your 40 miles includes highway driving - in other EVs, freeway-speed driving decreases the range by about 20%
- there will be some degradation as the batteries age - 80% capacity after 10 years would not surprise me