It appears the biggest saving is the use of direct drive motors. This eliminates losses from friction, slippage, etc. in power trains. No transmission, no differential. One of the biggest plusses about front wheel drive cars is the elimination of the hypoid rear axle. The hypoid gear set, unlike spur gears, relies on sliding of the gear tooth surfaces. This is why they require 90W gearlube and run so hot. Commutatorless electric motors, using Hall sensors and electronics instead of graphite-on-copper brush systems have really come a long way recently and efficiencies better than 90% are not uncommon.