 FACT: Doc says the DeLorean requires 1.21 gigawatts to make one  journey through time. A gigawatt, or 1,000,000,000 watts, is a unit  of power which defines the RATE at which energy is transferred. It  is meaningless as to how much fuel, electricity or "Mr. Fusion" is  required. Doc should specify an amount of time as to how long 1.21  gigawatts is being fed into the DeLorean, or used a different unit  such as gigajoules.