Musk is doubling down, expanding the capacity of the company’s main car-assembly plant in Fremont, California (which will eventually produce hundreds of thousands of cars a year), while building a factory-to-end-all-factories outside Reno, Nevada, that will produce battery packs for both cars and homes. Over the six days following Musk’s presentation, which was posted on YouTube and the company’s website, Tesla reportedly received reservations for $800 million worth of Powerwalls and Powerpacks, about what it makes in almost three months selling cars.
"I think we’ve really struck a note, without salespeople or advertising," Musk tells me. "With that you can do anything."
"Do you know the difference between power and energy?"
"Uh," I start to respond.
"Do you know the units?"
I’ve asked Musk a question about improvements in battery technology, but instead of an answer, he’s decided to give me a pop quiz.
When I offer the right answer for energy—"Joules?"—Musk smiles. "Hey!" he says. "Not bad. What’s power measured in?"
Silence.
"Watts," he says and then adds, admonishingly, "I mean, those are very important. Power is how fast you can run. Energy is how far you can run."
Musk is saying this to make a point. Unlike computer chips, which have improved wildly over the past decade, batteries have proved stubbornly resistant to huge jumps in performance and cost efficiency, in part because we ask so much of them. Today’s lithium-ion batteries must fit into tight spaces—either stuffed in a pouch behind an iPhone screen or, in the case of the Model S, lined up by the thousands in a battery pack that reportedly weighs more than 1,000 pounds and runs the length of the chassis. They must last for years. And they must be stable enough to perform well in extreme temperatures (and not burst into flames). Moore’s law, the principle that holds that computing capacity doubles every two years, does not apply. "The nature of battery innovation is that it tends to be incremental," says Musk. "It’s really rare that there’s a big breakthrough because there are so many constraints. You can easily improve, say, the power, but then it’d make the energy worse."
Musk generally relishes the role of sustainable-energy schoolmaster, but he seems more irritable than usual on this occasion, perhaps because he has spent the day at a Los Angeles County courthouse. Most people regard jury duty as an inconvenience; Musk, whose schedule requires him to split his time between SpaceX and Tesla while sharing custody of his five sons with his ex-wife, Justine Musk, looks like he just survived a natural disaster. "It’s a staggeringly inefficient process," he says, frowning.