The electric car-maker shut down the factory for two weeks in late summer to complete modifications to handle the addition of the all-wheel drive Dual Motor Model S.

The company says the added capacity also helps it accommodate stronger global demand, and the eventual start of Model X crossover production.

Tesla detailed the upgrades in a recent company blog post, saying they'll help it raise production by 50 percent by the end of 2015.

By its own estimation, Tesla built 22,000 cars last year and is on track to build 35,000 this year.

So the company's total 2015 production could be 85,000 cars or more.

That number will include some Model X electric crossover utility vehicles, but the bulk of the cars built are still likely to be Model S sedans.

Earlier this month, Tesla said it would delay first deliveries of the Model X until the third quarter of 2015.

The assembly-line and plant changes mostly focus on automation, including robots that can lift entire cars into position for different stages of assembly and install their battery packs.

These robots are named after X-Men characters because, Tesla says, "to us, these robots are like superheroes."