Most of it, it turns out. The dyno run, performed by the folks over at Dragtimes, showed 368 horsepower to the rear wheels, as shown on the dyno chart at the Dragtimes site (not the transposed 386 horsepower stated in the YouTube video title). While dynos are as variable as their owners, and can't necessarily be taken as absolute values, the potent figure illustrates the efficiency of a direct-drive system: less than 12 percent of the electric motor's power is lost in transmission to the rear wheels. That beats the typical 15-20 percent lost in most combustion engine cars on the way to the wheels.
The future of performance is undoubtedly electric, and the Tesla Model S Performance, in addition to being the first real electric car (in our estimation) is also well on its way to lighting that particularly bright path forward, too.