Porsche 918 Spyder

Supercars: sleek, blindingly fast, ultra-expensive objects of lust for 14-year-old boys and sober-suited executives alike. For decades, supercars were powered solely by gasoline. But now there's a new gang in town, and they've upended all the rules. The newest, coolest, most jaw-dropping supercars will come with one feature no Ferrari or Maserati or Lamborghini or Noble or Aston Martin has ever had. It's a charging cord. Here are six supercars--one in production now, five on the way--that use electric power for some or all of their motive power. Whether it's combined with a gasoline engine...