"Marty knew those [three] sonic booms all too well. He looked round for the source of the noise, and saw Doc Brown pull the DeLorean into the driveway. / But both Doc and the DeLorean were different! For one thing, the car had a new addition to its rear deck, right above the engine, a white canister labeled 'Mr. Fusion'. And Doc (as white-haired and disheveled as ever — at least that was the same!) was dressed in even wilder clothes than he usually wore; a metallic yellow shirt covered by a long orange robe." —From Back to the Future Part II by Craig Shaw Gardner (quote, page 9)

" The inventor didn't wait for Marty's answer [to his reply 'Back to the future!'], but walked quickly to the garbage can by the side of the driveway. He threw off the lid and began rifling through the can's contents. / "Wait a minute!" Marty called. "What are you doin', Doc?' / Doc picked up a banana skin and a crushed beer can. "I need fuel!" He carried the trash over to the 'Mr. Fusion' canister, dumped in the banana skin and remaining beer, then — after a moment's thought — the beer can, too. " —From Back to the Future Part II by Craig Shaw Gardner (quote, pages 9 and 10)

Marty: "Wait a minute, what are you doing, Doc?" Doc: "I need fuel!" — Marty and Doc, while Doc refuels Mr. Fusion with garbage

The Mr. Fusion Home Energy Reactor (also known simply as Mr. Fusion and the fusion generator) was the name of a power source used by the DeLorean time machine. The actual unit was manufactured by Fusion Industries.

History

Mr. Fusion converted household waste to power the time machine's flux capacitor and time circuits using nuclear fusion (it is thought that this is cold fusion), as well as allowing the DeLorean time machine to generate the required 1.21 gigawatts to travel through the space-time continuum. The energy produced by Mr. Fusion replaced plutonium as the primary power source of the DeLorean's time travel and flight capabilities.

Note: The following section is considered non-canon or is disputed in canonicity.

On August 8, 2015, Dr. Emmett Brown won first prize at the Hill Valley 1980s Car Expo with his DeLorean, which was 10% off a hover conversion worth $3995.00 at Goldie Wilson Hover Conversion Systems. To get the money he needed for this and the Mr. Fusion, which he had spotted in a store window for $8200 and considered ideal for solving all of his electrical energy needs, Doc searched the internet for the best investment to make, then traveled back to April 18, 1938 to pick up several new copies of Action Comics issue #1.

He sold one copy in 2015 or beyond to get the money he needed, and then traveled to 2015 or beyond, and sold another at Southby's Auction House for $2.5 million dollars.

Non-canon or disputable information ends here.

Mr. Fusion was first seen when Doc returned back from 2015. He rummaged through the McFly residence's trashcan to find a banana peel, a Miller beer can (pouring in the remains of the beer, and then dropping the can in as well), and some other pieces of garbage which he dropped into the unit before closing it. This suggests that the Mr. Fusion unit could run on pure trash.

When Doc, Marty McFly and Jennifer Parker arrived in the year 2015, a few logos are spotted for Fusion Industries on the power generators in the alleyway they landed in. The generators resembled the shape of a very small truck.

Behind the scenes