Tesla will deliver the first Model 3s to eager buyers tonight, but you don’t have to wait until supper time on the West Coast to find out new details. While updating the Tesla website in advance of tonight’s event, some poor developer leaked the Model 3’s power efficiency, which hints at a truly impressive range for the baby Tesla.

Source code on Tesla’s website, spotted by Electrek but since removed, points to the Model 3 having an efficiency of 237 Wh per mile, way more efficient than the power draw of the Model S and Model X, which use 344 and 367 Wh respectively.

Electric vehicle efficiency is exactly like the miles per gallon of a conventional car: the more efficient, the better. Even though the Model 3 is expected to come with smaller battery options than the Model S and Model X, the far superior efficiency could give it a range of over 300 miles.

That efficiency could come at the cost of lower acceleration and fewer heavy gizmos compared to the Model S and X, but Tesla has been saying for a while that the Model 3 won’t have all the same bells and whistles. Some of that is for cost reasons, but if it means a crazy-good range with a relatively cheap battery pack, I’m willing to believe that most buyers will take the tradeoff.

Chris Mills has loved tinkering with technology ever since he worked out how to defeat the parental controls on his parents' internet. He's blogged his way through Apple events and SpaceX launches ever since, and still keeps a bizarre fondness for the Palm Pre.