According to the first Iron Man movie, the janky Arc reactor Tony Stark made in a cave put out three gigajoules per second. A joule is a unit of energy equal to one watt of power per second. A gigajoule is equal to one billion joules, or one billion watts of power per second. So Tony’s handmade Arc reactor put out three billion watts (three gigawatts) per second. His refined reactor? Maybe twice that. Dr. Emmet Brown only needed 1.21 gigawatts to travel through time. Tony Stark has a power source the size and weight of a donut that puts out more power than a nuclear reactor. I’m pretty sure he would replace the 900-pound battery pack in a Tesla with a 16-ounce arc reactor to make the fastest car ever. And he would never need to recharge. Just sayin’.