Flux energy was a byproduct of time travel. This energy would build up when traveling through time, however it was more prevalent when traveling to the past.

On November 5, 1955, Emmett Brown came up with the idea of the flux capacitor after slipping and bumping his head while standing on his toilet to hang a clock. The idea came to him in a vision he had after being knocked out. He drew an inverted Y-shape with wires and stated "flux compression". He also performed some mild calculations on the paper.

Since coming up with the idea, Doc spent many years and most of his family fortune trying to get it to work. By 1962, he had invented the temporal field capacitor. It was a prototype time machine that was able to send objects through time, but only during the lifespan of the device. It could only send objects forward through time, as sending objects even a few minutes into the past would cause a buildup of flux energy. If an object was sent any further back than that, the arrival of the object would overheat the capacitor and start an electrical fire.

By 1985, Doc had managed to make his idea into a reality. The final flux capacitor design solved the problem with the build up of flux energy, allowing time travel to the future, as well as the past. By this time, he had also invented a time machine that allowed life forms to travel through time.

The DeLorean time machine contained the flux capacitor, which consisted of a box, connected to the capacitor drive, with three small, flashing incandescent lamps arranged as a "Y", located above and behind the passenger's seat. As the car neared 88 miles per hour, the light of the flux capacitor pulsed faster until it had a steady stream of light, which one was not supposed to look at as indicated by the Dymo warning label placed across the glass panel. The stainless steel body of the DeLorean also had a beneficial effect on the flux dispersal as the capacitor activated.