On Monday, BMW rolled out their first fully electric car, the i3 — but the most impressive part of the rollout may not have been visible onstage. On the heels of the launch, Bloomberg News turned up an interesting detail: an optional "mobility package" that would let buyers pay to have access to a gas-powered BMW X5, in case they're planning a trip beyond the limits of the i3's battery. In short, if you need a non-electric car for the weekend, they'll bring you one.

It's not the first time this has been tried: Fiat unveiled a scaled-down version of the same plan in April. But if you're unfamiliar with the politics of electric cars, it might seem like a strange move. You don't offer to rent laptops to tablet buyers, for instance, or pickup trucks to hybrid owners. But within the industry, it's being seen as a chance to patch up electric vehicles' perception problems with small-scale car-sharing, a prospect that's being called, "one of the great possibilities in alternative transportation." So why is BMW's rental plan getting so much love?

The problem is as much psychology as battery tech. One study found that in a given year, 60 percent of drivers will never drive more than 250 miles in a day — exactly the range of the Tesla Model S. There's also reason to believe that, year over year, they're mostly the same people. A 2011 McKinsey report pointed to potential EV buyers in New York, Paris, and Shanghai that rarely drive far enough to bring range into play. In a later interview, the report's author pointed out, "If you independently tracked how far consumers drive in their cars, it's often less than what they believe."

But that's just the problem. There's a mismatch between how much range drivers really need, and how much they think they'll need — and when they're considering which car to buy, they put more weight on the second one. Drivers like to think about taking their cars cross-country, even if they rarely do. It's something BMW knows particularly well, having funded a study on the psychological barriers to EV adoption. According to the study, it boils down to issues of control. Once subjects had adapted to their cars' comfortable range, the study found they "experienced range somewhat more like a problem-solving task rather than as a stressful encounter." In the case of those hypothetical long-range trips, the issue becomes giving drivers some way to solve the problem.

In that light, BMW's dip into car-sharing makes a lot of sense. BMW's i3 has less than half the range of the Model S but they're betting that buyers will be more comfortable if they know they can book a gas guzzler whenever they need to go farther. It's a particularly good bet because, as McKinsey tells us, they probably won't take BMW up on it all that often. They just want to know they can if they need to. It's still a bet, and it's far from a sure thing: lots of drivers will balk at the 100-mile range, and many may find car-sharing too complex to bother with. But tricky adoption problems call for creative solutions, and if it works, BMW will have cracked a puzzle that the rest of the industry is still struggling to figure out.