Maybe Elon Musk predicts unlikely and seemingly impossible Tesla production numbers because he’s got some secrets he hasn’t revealed quite yet.

Tesla announced yesterday that all of the 70 kilowatt-hour Model S cars they have sold for the past month actually be upgraded to a 75 kWh battery. The 75 kWh rumors started on Monday when a California emissions website listed the option, but Tesla didn’t care to elaborate on how they would handle the production aspect. Turns out people had the 75 kWh battery the whole time, they just have to pay Tesla for a remote upgrade.

The upgrade costs $3,000 and adds another 15 miles per charge to the range of the car. That’s $200 per mile. For people who recently bought their Model S and are willing to drop the extra cash, all they have to do is wirelessly upgrade. Tesla dealers don’t even have to touch the hardware (though you can bring the car into a Tesla dealer after upgrading if you want to replace your “70” logo with a “75”).

Fork it up.

The upgrade — though sneaky — is the ideal system for Tesla. People like to have choices, and the 75 kWh battery gives them a choice without making the Tesla factory figure out how it will produce another iteration on the model.

Musk told investors that he wants to move as much of the manufacturing in-house as he can, and creating one battery is a way to do that. The Model X also has a 75 kWh option, so Tesla can use the same battery pack for both.

Tesla clearly already has its hands full with the Model 3 demand, the botched Model X rollout, and a Musk-spoken guarantee the company won’t be profitable this year.

Despite all that, Musk sounded overwhelmingly confident in the company during the first quarter earnings call (even if he does neurotically keep a sleeping bag at his desk on the factory floor). Maybe that confidence comes from a longer list of secrets lurking in the Teslas already on the road.

the 75 kWh battery lets you do this for 15 more miles.

Tesla made a similar move with the Autopilot software. Autopilot can be downloaded remotely for $3,000, and upgrades to Autopilot come over the wireless network, as well.

Teasing Tesla owners with upgrades just beyond a paywall is a power play that seems to have worked for Autopilot. But Autopilot is an advanced semi-autonomous driving system. Five extra kWh is just 15 extra miles. Still, paywalls seem to be working better for Tesla than they do for the newspaper business.

A Tesla spokesperson told The Verge that the company will continue to offer the 70 kWh option, but will only make models that fit 75 kWh battery packs. It’s “a decision that is the most efficient for Tesla and the most beneficial for our customers.”

But you have to wonder: What else is Tesla hiding underneath those sleek ergonomic car bodies?

Photos via Tesla (1, 2)