Electric delivery vehicles are a possibility of the future, which is why we are currently testing the feasibility via the electric passenger vehicle (the only pure EV available is the Tesla Roadster).
Our typical market served requires a 150mile round-trip capability. Currently the trucks being tested or shown in auto-shows have a 100mile range (and that is not descriptive of the load they may carry).
This link provides a glimpse at what may be to come for larger vehicles, and this link shows that smaller delivery vehicles powered by electricity (solely) are becoming available (to fleet owners).
Images drawn from and copyright autoblog.com