If the number is not going to be useful to the consumer, then there's no reason to mandate it be on the sticker. Having some sort of number there is useful; as

If the number is not going to be useful to the consumer, then there's no reason to mandate it be on the sticker. Having some sort of number there is useful; as electric cars become more common we'll need some way of comparing their efficiency. Right now you can find out that the Volt at 93 "mpge" is slightly less efficient than the Nissan Leaf at 99 "mpge". I'd still much rather have it in the less ambiguous units of miles per kilowatt hour. (Or if they really want to appeal to physicists, they should give it in units of inverse force. 1 mile per kilowatt hour = 447.04 inverse MegaNewtons.)