The other night, for the first time in years, I filled my gas tank for under $30. I was happy, but as I surveyed my decaying Honda Fit under the gas station fluorescents, a thought flickered through my mind: "It would still be cool to own a Tesla."

Not that I could afford one, whatever the price of gas. But that "still" spells trouble for Tesla Motors. The electric car-maker's stature has risen—along with its share price—at a time when US gas prices were hitting record highs and appeared to be there to stay. But as a surge in domestic oil production has driven down the cost of filling up, Tesla is facing a question it really hasn't had to contend with since becoming a public company in 2010: If gas is cheap, why would anyone need to own an electric car?

Wall Street certainly seems to be wondering the same thing. The price of Tesla shares has fallen by nearly 20 percent since mid-November, ending Tuesday slightly up after falling for seven straight trading days. "We believe the recent decline in TSLA shares is largely driven by the concern low gasoline prices could impact demand if sustained for the long term," writes Ben Kallo, an analyst for Baird Equity Research, in a note to investors.

The most obvious counterargument in Tesla's favor is that if you can afford a $70,000 Model S anyway, $30 for a tank of gas versus $60 probably doesn't matter that much to you anyway. You're buying an electric car out of a sense of environmental responsibility. And you're buying a Tesla for the experience of driving a car with a user experience like no other, regardless of fuel source.

"Tesla vehicles are purchased for performance, quality, and brand, which are minimally affected by oil prices," Kallo writes. He also calculates that Model S owners will still save nearly $1,400 annually even at the current average gas price of $2.78 per gallon.

But as WIRED's Alex Davies found out from his own experience, the inconvenience of simply keeping an electric car powered up can outweigh any other hoped-for advantage. The electric-car infrastructure in the US is still in its infancy. And if gas stays cheap, the pitch for building out that infrastructure will be harder to make.

If drivers can already find an inexpensive fuel source on nearly every street corner, they lose the biggest incentive for seeking out alternatives. Without mass market demand, charging stations remain scarce compared to gas pumps, and driving an electric car, including a Tesla, remains an exercise in planning ahead. No matter how great the car, not having a place to charge it will leave you stranded. Perhaps the experience of driving a Tesla trumps any hassle. But until gas prices tick up again, the company will have to work harder than ever to prove it.