As the Model S family has expanded over time it has become more relevant to compare range from one variant to another with a consistent set of assumptions so our customers can know what to expect and make the best decision to fit their needs. This can be a bit difficult since the background test methodology and standards from the US EPA are evolving over time. There are also many customer vehicle configuration choices, both before and after purchase, that can affect range as much as or more than the vehicle platform choice itself.
Battery technology has continued a steady improvement in recent years, as has our experience in optimizing total vehicle efficiency through Model S development. We have long been excited to apply our learning back to our first vehicle, and are thrilled to do just that with the prototype Roadster 3.0 package. It consists of three main improvement areas.
At an event in Los Angeles last year, we showcased battery swap technology to demonstrate that it's possible to replace a Model S battery in less time than it takes to fill a gas tank. This technology allows Model S owners in need of a battery charge the choice of either fast or free. The free long distance travel option is already well covered by our growing Supercharger network, which is now at 312 stations with more than 1,748 Superchargers worldwide. They allow Model S drivers to charge at 400 miles per hour. Now we're starting exploratory work on the fast option.