Let's say up front that the 87-mile single-charge range of the Mercedes-Benz actually stacks up nicely against its competition, since that distance puts the new model right in line with the Nissan Leaf and BMW i3 (we'll ignore the Tesla Model S for a second, here). You can find the numbers at the US Department of Energy's FuelEconomy website.
As far as miles per gallon equivalent ratings, though, the Benz's steel frame makes it come up short, as it's about 1,300 pounds heavier than the carbon-fiber-body i3 and about 600 pounds heavier than the Leaf. The B-Class EV has a bigger battery than the i3 or the Leaf (36 kWh compared to 22 kWh for the i3 and 24 kWh for the Leaf) and that's one reason the car gets an 84 MPGe rating, which is about 26 percent less than the Leaf's and 32 percent less than the i3's. But at least the local utility companies will be happy.
Mercedes-Benz priced the 177-horsepower B-Class ED in April at $41,450, or $100 more than the i3. Check out Autoblog's First Drive impressions here.