From
Chevrolet.com:
"Volt
is an electric car that can create its own electricity. Plug it in, let
it charge overnight, and it's ready to run on a pure electric charge
for up to 40 miles(3) - gas and emissions free. After that, Volt keeps
going, even if you can't plug it in. Volt uses a range-extending gas
generator that produces enough energy to power it for hundreds of miles
on a single tank of gas.
Who will get the most benefit from driving Volt?If
you plug in frequently, you'll experience the greatest gas savings and
reduced emissions. Per mile, electricity is less expensive to use than
gas, so if you can plug in before or shortly after the electric charge
runs out, you'll get the maximum benefit out of Volt.
Is it easy to use?Yes.
While Volt has been designed to be the most efficient when it's plugged
in daily (like a typical electric vehicle), it will run efficiently
without being plugged in for days, weeks or even months. With Volt, you
don't have to be tied to plugging-in every day if it doesn't
accommodate your schedule."
Read More at Chevrolet.com