B mode is great for "one pedal" driving. I use it all the time, especially in slow and go on the freeway. Differences in energy consumption between B mode, D mode, and shifting to N for coasting really depend upon driving style. If you hold the accelerator in the neutral position where there is no power in or out when coasting, it is the same as shifting to neutral and it does not matter whether you are in D or B mode. If you tend to move the accelerator pedal more than necessary to hold a steady speed, then D mode and shifting to neutral may improve efficiency under certain conditions compared to B mode.
Silver LEAF 2011 SL rear ended (totaled) by in-attentive driver 1/4/2015 at 50,422 miles
Silver LEAF 2015 SL purchased 2/7/2015