This could be the next big upgrade for the Tesla Model S and Model X

The Tesla Model S and Model X may be getting longer ranges in the near future.

Tesla is preparing to release a 100 kWh battery option for both the Model S and Model X, according to new evidence first spotted by Dutch blog Kenteken.TV. The blog reports that RDW, the Dutch authority responsible for vehicle registrations, has approved a 100 kWh battery option for both Tesla cars.

The new battery option could extend the range of the Model S to as much as 380 miles - a pretty major bump from the 270-mile range offered by the Tesla's most powerful Model S, the P90D.

Kenteken.TV got the information from RDW's published database of approved vehicles that can be sold in the European Union. In the list is a number of Tesla Models, including entries for a 100D for the Model S and 100X for the Model X.

The understanding has been if the P90D was named for its 90 kWh battery, then it's reasonable to assume a P100D would mean a 100 kWh battery is in the works.

This isn't the first time we've caught wind that Tesla is working on a 100 kWh battery option for the Model S. In March, a hacker found a mention of a P100D in the software that runs the cars, hinting that a Tesla with a more powerful 100 kWh battery could be on the way.

For Tesla CEO Elon Musk's part, he didn't seem particularly flustered by the find. When Hughes' car started downloading a new software update against Hughes' wishes, he thought Tesla was punishing him for the find. Musk tweeted back that wasn't his call and commended him for his hacking skills.

Tesla did not immediately respond to a request for comment.