If you want a fast and sexy yet usable and practical electric vehicle, there's really only one option: Tesla. That's all about to change, however, because Jaguar's all new, all-electric I-Pace, which goes on sale next year, is a legitimate Tesla rival. How do we know? We've been in one.

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Jaguar engineers took time out from final calibration testing to give us a ride around Los Angeles in one of the first I-Paces built using production tooling. We weren't allowed behind the wheel, but after riding along with powertrain program manager Simon Patel on streets and roads we know very well, we can tell you the I-Pace is quick and quiet, with a nicely buttoned down chassis and a remarkably composed ride.

It's difficult to overstate the significance of the I-Pace. This truly is a moonshot Jaguar, the most profoundly radical car in the company's history. More than that, it puts Jaguar—an automaker that opened the 21st century building cars soaked in 1960s nostalgia—right at the bleeding edge of mainstream automotive industry product development trends. Daimler, BMW, Porsche, and other premium brand automakers are all working on all-electric Tesla rivals of their own. But Jaguar got there first.

The I-Pace is powered by two electric motors—e-machines, in Jaguar parlance—one driving the front wheels and one driving the rear through concentric drive transmissions. The permanent magnet motors were developed in-house at Jaguar, along with the battery concept and design and all the software that controls the powertrain and manages the battery. Jaguar isn't revealing system output numbers yet, but Patel confirms the production I-Pace will have close to the 400 hp and 516 lb-ft quoted for the concept version unveiled in 2016 and a range of 300 miles.

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The powertrain is optimized for efficiency, with a 50/50 front to rear torque split under normal running. But the driveline management software, dubbed Intelligent Driveline Dynamics, will automatically vary the torque split between the two axles to allow for sporty driving or cope with low-friction surfaces. The system also allows torque vectoring by braking to enhance agility and stability through corners. Two regenerative braking modes will be available—Normal, which replicates the coast-down feel of an internal combustion engine car, and Regen B, which allows for single-pedal driving.

Although Tesla uses induction motors that don't need rare earths, Patel says Jaguar has opted for the slightly more costly permanent magnet e-machine design because it offers better power density and up to 5 percent better efficiency. Similarly, the I-Pace's concentric transmissions are also more complex and expensive than the step-gear transmissions used by Telsa. But because they directly align the e-motors with the axles, less power is lost through the driveline. They also deliver a more compact powertrain module.

Most of the 500 Jaguar engineers dedicated to the I-Pace program started their careers designing and engineering cars powered by internal combustion engines. In fact, Simon Patel actually designed internal combustion engines, crossing over into the world of e-machines while working on JLR's new PHEV powertrains. Creating an electric vehicle in house, from scratch, presented the team with some unique engineering challenges.

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Managing noise, vibration, and harshness was one. Patel says the I-Pace is 6dB to 8dB quieter that a regular Jaguar, so noises usually lost in the soundscape of an internal combustion engine are more apparent. The e-motor and transmission units therefore rest on double-isolated mounts, and Patel says a lot of time was spent honing the microgeometry of the transmission gears and figuring out the best way of putting them into the transmission housing, not just to reduce the gear whine endemic to electric powertrains but also to tune it to make it sound, er ... sporty.

The I-Pace is whisper quiet while cruising under light power loads. But when Patel plants his right foot—and the I-Pace surges forward with an urgency that suggests the claimed 4.0-second 0-60-mph acceleration time is legit—there's a gentle whirr that builds in pitch as speed increases. This is what electric performance sounds like, apparently.

We can't tell you anything about steering or brake feel, but from the passenger seat, it's clear JLR dynamics guru Mike Cross has spent a lot of time on the chassis. An electric vehicle exhibits different pitch behavior from that of an internal combustion engine vehicle on throttle lift off and corner entry, says Patel, and a lot of effort has gone into making the I-Pace feel as familiar as possible. Even when he deliberately exaggerates steering, braking, and throttle inputs on our drive loop, the I-Pace responds with roll, dive, and squat motions that have an impressive measured calmness to them.

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If anything, the I-Pace feels to be one of the better-riding modern Jaguars, at least on L.A. 's choppy tarmac. Our car was rolling on the air suspension and 22-inch wheels and 255/40 Pirelli P Zero tires that will be standard on top-spec models, but it displayed excellent compliance and impressively subdued impact harshness. Mass helps. As with all electric vehicles, the I-Pace is relatively heavy (though Jaguar isn't saying how much it weighs), but, says Patel, having all those batteries under the floor means the I-Pace's center of gravity is effectively 4 inches lower than that of the F-Pace. It should go around corners quite well ...

Jaguar calls the I-Pace a crossover. That's apt. It has all-wheel drive, and it's a tall wagon. But it's not quite as tall as an F-Pace, and it doesn't look as off-road capable. As you're riding atop the battery pack, the seating position is higher than that of a regular car, and the low cowl and beltline help deliver a commanding view of the road. We can't tell you much more about the interior, other than the steering wheel looks like familiar Jaguar hardware, and the instrument panel is the 12.1-inch TFT screen that's used in current top-spec Jags. Everything else inside was covered in heavy black felt.

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Jaguar currently has a total of 200 I-Pace prototypes on the road, cars that have covered a total of 1.5 million test miles. Production is being slowly ramped up at the Magna Steyr plant in Graz, Austria, where it will be built, and pricing will be announced in March. A bold new chapter in the history of one of the world's most iconic sports-luxury automakers is about to be written.

Should Tesla be worried? Yes ... and no. The Jaguar I-Pace signals the beginning of the end of Tesla's hegemony in the premium, high-performance electric vehicle market. And on first acquaintance, it feels every bit as accomplished as, and perhaps even more refined than, the Silicon Valley superstar. But Tesla's first mover advantage has given it a fanatical following, and it offers variants with considerably more performance.

Let's just say Tesla's on notice; The Jaguar I-Pace shows it's going to have to work a lot harder to remain ahead of the game.