According to site Earth2Tech, Musk asserted that the Leaf's battery tech is "much more primitive" even when compared with Tesla's early prototypes, and says he expects to beat Nissan's cost per kilowatt hour.

Musk's assertion is that the Leaf's air cooling system for thermal management, as opposed to the Roadster's (and the Chevy Volt's) liquid cooling system, will lead to huge temperature disparities and subsequent efficiency degradation in cold environments -- something that reportedly was a big problem for the electric MINI Cooper. Musk even went so far to say that the Leaf's battery would essentially "shut off" in hot environments.

Nissan has reportedly put the Leaf through the wringer with vigorous testing to ensure that the vehicle's battery is up to snuff, and is backing up its engineering with an 8-year, 100,000-mile warranty on the battery. The proof either way won't be known until the Leaf hits lots and we have real-world customer feedback to go on. Until then, two things are certain: The viability and functionality of electric vehicles will remain a hot topic, and Musk will say whatever he needs to to keep Tesla in the news.