Hey, Porsche just found a reason that coupe-SUVs exist!

If – like us at TopGear.com – you’ve been baffled by the existence of the ‘coupe SUV’ ever since the BMW X6 invaded our lives back in 2008, then prepare to be amazed. Porsche has just revealed the new Cayenne Coupe EV and come up with a mathematical reason to buy one instead of the SUV version.

Not if you like headroom, obviously. What Porsche reckons is a “gently sloping roofline sweeping elegantly over the car’s broad shoulders” apparently inspired by the silhouette of the 911 is never going to be as roomy as a boxy SUV. Visibility will also be of the ‘did I put my hoodie on back to front?’ sort.

And you don’t get any more power – not that any Cayenne Electric is short of ponies. In fact, it’s verging on the absurd. The standard car, simply called Cayenne Coupe, makes do with 402bhp from its twin motors. That’s boosted to 436bhp if you use launch control, to hit 62mph in 4.8 seconds. And that’s the base model.

Spec the Cayenne S instead and you’re up to 537bhp normally, 657bhp when you clog it from rest, and 3.8 seconds to 62mph. Which is clearly not enough, because there’s a Turbo version.

This Cayenne Coupe matches the SUV’s numbers – the most powerful Porsche yet – and delivers an 1,140bhp wallop in ‘watch this!’ mode, or a mere 845bhp in daily driving. It’ll make your cramped passengers go from scared to nauseous in just 2.5 seconds.

And we’ve even heard there’s a sillier version still to come, perhaps badged Turbo GT, with over 1,200bhp. Why? Because like the scientists in Jurassic Park who resurrected man-eating dinosaurs, Porsche’s engineers asked whether or not they ‘could’, not whether or not they ‘should’…

But power or practicality aren’t the reasons this car confounds coupe-SUV pointlessness. Nor is the dashboard, with its curvy melted touchscreens, or the prices, which stretch from an £86,200 base price to £133k for the Turbo. You’re paying about £6k extra to look like a 911 crossed with a hot air balloon.

No, it’s drag. Drag and range. Y’see, the Cayenne Coupe is slipperier than the SUV. Despite being as bluff up front as a football stadium (and almost as heavy) it slips through the air with a drag factor of 0.23Cd. That’s 0.02Cd better than the non-Coupe.

This buys you a whole 11 miles more range, and all you have to sacrifice is room for human heads and around 200 litres of boot space. You’ll have cargo anxiety, but a bit less range anxiety, thanks to up to 415 miles on a charge.

So there you have it. It only took the best part of two decades for a coupe-ish SUV to find a reason to exist. If you prefer versatility, here's why the regular, slightly cheaper Cayenne Electric is the very best e-SUV you can buy…