It's right in the Post Office press release, explaining how they are cheaper.
And they are not gas guzzling. They get slightly better gas millage then the current vehicle with the A/C on. The entire freak out some people are having is over that.
With the A/C off they do way better than the current ones.
The Post Office has become so politicized it leaves people unable to do basic math.
I fail to see how buying gas guzzling vehicles over electric ones will save money in the long term.