What powers the modified DeLorean is a device called Mr. Fusion, which has the aesthetics and form factor of a household appliance. It is mounted to the back window of the DeLorean. At the beginning of the movie, Doc roots through a nearby garbage can to grab a banana peel and some beer. He rocks the top backwards on its hinge and dumps the items into its cylindrical reservoir, and closes it.
The device has the easy affordances of a consumer device. Doc flips it up, drops some beer and banana peels into a hollow, and snaps it shut. That’s it. There is no lock, no activation, no authorization. The device is hacked by Doc Brown, but you would expect anything outputting 1.21 Gigawatts to have some safety features in the off-the-shelf version.
Presuming it’s meant to power a house or even a car, I do wonder why it’s this size. You might want to have a bigger container to contain as much compost as possible to minimize the times it needs refilling. Of course we know this was a joke about the “Mr. Coffee” appliance available at the time, but if Tesla is eyeballing this as a model, it should take this into consideration.