"Prior to September 2014, the brake boosters in Tesla vehicles used vacuum, as in many other cars. After that, they switched to an electrical design. Since the cars don’t have combustion engines, ultimately even the vacuum was created as a result of electrical activity, so regardless of which brake booster is used, there is electricity used to decrease the force needed on the brake pedal. The electricity is not needed since the car would stop without it, but it makes it easier to drive. Ultimately, more electricity is generated stopping the car than is used to make it possible to stop the car without as much force on the brake pedal."
They also have regenerative braking so pads can be softer and less assist is required.
Your question has intrigued me though, so I will research the subject for my own edification!