Ever see one of these in operation? According to the news release, they are being tested in three cities: New York, LA and Suburban Virginia.

While it may be commendable to show off electric vehicles, I haven't yet seen the pricetag for such a truck. My suspicion is that the dollar amount to purchase such an electric vehicle will far exceed any savings as compared to using a similar sized gasoline powered vehicle. I suppose time will tell as to whether or not these vehicles will ever see regular use.
The USPS has budgetary considerations on one hand and a commitment to "green" technology (such as electric vehicles) on the other. It will be interesting to see which option wins out when new USPS trucks are purchased.