Tesla Motors sold 22,477 Model S sedans last year. As you'd imagine, many of the people buying the super-luxe car owned German vehicles before going electric. But many more of them owned a Toyota Prius.

Al Pace was among them. Pace, a real estate developer from Palo Alto, California, was a longtime fan of the little hybrid that could. He'd owned two of them in the six years before buying his Pearl White Model S P85. He loved the Prius, but kept a close eye on Tesla as it launched the Model S. He placed a deposit and rescinded it, twice, before pulling the trigger early last year.

"Two things served as a catalyst for me to get over the hump," Pace tells WIRED. "I needed something larger, and about that time, Elon Musk made the commitment to back it financially." That was the clincher and he couldn't be happier.

"I've been the beneficiary of a number of nice cars over the years, but I like [the Model S] more and more," says Pace. "It gets better as I drive it. There's this ongoing subtle reveal of nuanced engineering. It's a kind of automotive strip tease."

Pace is a typical Tesla customer. Most of Teslas' conquest sales–sales made to customers who previously owned another brand–are from Toyota, according to Polk Automotive. Of those, Prius defectors lead the pack.

"The pure conquest data show that the Model S is conquesting owners of Toyota vehicles more frequently than owners of any other brand," said Polk Automotive analyst Tom Libby. "The Prius is at the top of that list, with the Toyota Highlander SUV and Sienna minivan ranking fifth and sixth overall."

All told, Toyota accounts for 15.51 percent of Model S conquest sales. Mercedes-Benz and BMW follow with a little more than 10 percent apiece. Libby posits that Prius owners want a hybrid or electric vehicle, but want something more luxurious and stylish. The Honda Fit EV, Ford Focus Electric, Fiat 500E, and the Nissan Leaf just don't cut it. Part of that is the audience: As Libby notes, "Model S buyers are very well-off financially," and their garages have housed everything from Aston Martins and Bentleys to Ferraris and McLarens.

Tesla "was among the top-selling luxury brands in [California] in 2013," says Kelley Blue Book's Senior Insights Director Karl Brauer, "which means it’s cutting across every luxury manufacturer out there."

Tesla owner Al Pace driving through Palo Alto. Photo: Ariel Zambelich/WIRED

It should be noted that Tesla's conquests are no threat to the world's largest automaker. The Prius family of vehicles sold 234,228 cars in 2013, and sold more than 69,000 in California alone. That's three times as many cars as Tesla has sold since its founding in 2003. That said, Tesla's growth has to come at someone's expense, and the company will only poach more customers, and many of them will come from Toyota. The forthcoming Tesla Model X crossover utility vehicle, which has even more room and a pair of innovative "falcon" doors that open like the wings of a bird, is poised to steal more Toyota owners, and also grab people who own or are shopping for the Lexus RX 450h hybrid crossover.

"That car has long held the 'wealthy green person who wants a premium badge and/or more space than a Prius' role," Brauer says. "It’s an existing luxury crossover with advanced/alternative drivetrain technology. Interest in the RX 450h makes up a disproportionate number of RX sales in the Golden State, and I suspect it will make up a disproportionate number of Tesla Model X replacements when that model goes on sale next year."

And Tesla CEO Elon Musk expects sales of the Model X to outpace the S.

"Model X demand is very high," Musk said during a Q4 earnings call last month. "But there's a number–obviously, we don't disclose it, but even though there's 0 marketing for the Model X–essentially, it's like if you're going fishing, it's like the fish are jumping in the boat. We're not actually trying to sell the Model X at all, but demand seems to be remarkably high. And we're seeing a steady accumulation of Model X deposits."

With that kind of momentum, Tesla Motors could become an irritant for other automakers, particularly if and when Tesla's "Gen 3" car goes on sale sometime in 2016 or 2017. That model, widely but unofficially called the Model E, will be a mass-market car aimed at the Audi A4, BMW 3 Series, and Mercedes-Benz C-Class. With an expected sticker price of around $40,000 and a range of about 200 miles, the E could poach less affluent Prius owners, along with folks driving a Chevrolet Volt and other cars with cords.

"I think Model E will capture even more Prius folks, plus every other $30,000-$40,000 hybrid or electric vehicle," says Brauer. "The big question with the Model E will be whether or not they can really get 200 miles from an electric car that costs $40,000."

Of course, by that point, most automakers will have some kind of plug-in hybrid or full-fledged EV. As the technology advances, the tables could turn and you might see someone poaching customers back from Tesla.

"All the other guys are working on better range and reduced costs, too," says Brauer. "It’s entirely possible that by the time the Model E arrives there will be a Toyota or Ford or BMW that offers over 150 miles of real-world driving range for under $50,000. If that happens even the Model E with 200 miles at $40,000 won’t be all that unique."

As for Toyota, no one there seems terribly worried about Tesla's conquests.

"Perhaps prior to Tesla, there wasn't a good, dominant eco choice for the affluent consumers except the Prius, and now we are seeing these affluent folks move to Tesla," a Toyota spokesman says. "Prius’ mission was always to find appeal to an everyday, more mainstream buyer, and not necessarily the super affluent. The Polk sales data in the State of California validates that Prius is succeeding in its mission."

But so too is Tesla. Pace already is looking at his next car.

"The Model X is very high on my list right now," he says. "If the range is there, I wouldn't hesitate."