Currently, self-driving vehicles do not run exclusively on gas. They are all either hybrids or electric. Hybrid vehicles use gasoline as well as electric power.
Experts predict all self-driving cars will be electric in the future. In fact, self-driving car companies like Tesla, Waymo, and Cruise have all committed to electric vehicles only moving forward.
Since the complex sensors and computer systems used in autonomous vehicles require a lot of power, an electric battery is a more reliable power source than internal combustion engines. The transition to all-electric isn’t as straightforward as it sounds, though—these computer systems also suck up a lot of energy, which decreases their driving range on a single charge.