Elon Musk — Tesla's co-founder, CEO, and one-man PR machine — made news yesterday with a tweet that his company would reveal a firmware update for its Model S sedan later this week that will "end range anxiety."

"Range anxiety" is the notion that you're always worried you won't find a charger for your electric car before the juice runs out. It's a more serious problem for the many EVs on the road with sub-100-mile ranges like the Nissan Leaf, VW e-Golf, and Ford Focus Electric, but even the Model S — which has a range of 200 miles or more, depending on configuration — gets roped into the conversation. Perhaps it's because if you do run out of power, you can't just walk a few blocks to the nearest gas station, fill up a canister, and bring it back to your car; perhaps it's that even the fastest Supercharger isn't as fast as topping off a tank. Regardless, "range anxiety" is the boogeyman used more than any other to throw a wet blanket on the EV industry. It's a major reason General Motors has plowed billions into the "extended-range electric" Voltec platform, which combines an electric drivetrain with gas for backup.

"Ending" range anxiety, as Musk teases, isn't a simple matter. It's not a question of simply squeezing a few more miles of range out of the Model S's batteries with more efficient motor control, as could be delivered by a firmware update. A Model S could get 350 or 400 miles between charges, but you'd still run into the same issues that you do at 250: when you're getting low, what do you do if you're not close enough to a charger? What if you can't charge quickly enough?

That's why I don't believe that the firmware update will just extend range. Perhaps it will do that — it certainly wouldn't be unprecedented for improved range to come from software alone — but there will probably be other components to it as well.

A simple concept would be a driver-selectable reserve. If Tesla was able to squeeze, say, another 15 miles out of the battery with improved efficiency in firmware, but it socked those miles away in a reserve rather than simply adding them to the car's indicated range, that could give drivers some peace of mind. That way, if the car's about to turn itself off and you still can't get to a charger — or at least a safe place — you press a button on the car's control panel to unlock the emergency supply of extra power.

But that's not very smart, and I suspect Musk wants something that's bulletproof here — something the driver doesn't really have to think about. What if the car continually calculated your available range versus distance to home or a Supercharger, and warned you when you were in danger of straying too far? The car's navigation system can already take Superchargers into account when planning routes, but a constant red-yellow-green indicator in the instrument cluster could make a big difference. Being told that you need to start looking for a charger with 100 miles left is a lot less stressful than seeing the same message with 5 or 10 miles left.

The Supercharger network is only so large, though. It's also possible that Tesla has found a way to charge a bit faster from Level 2 charging stations, which have grown ubiquitous in even small- to medium-sized towns — the problem is that they can take many hours to top off the battery. I wouldn't expect miracles here, but then again, it's Elon Musk. Who knows?

Clearly, a range bump is the easiest and most obvious thing to offer as a firmware update. But you probably don't hold a press conference to announce something like that — I suspect this is bigger. We'll know more on Thursday.

Verge Video: Driving the Tesla Model S