"Oh, and by the way, we have a security feature in the restaurant, that limits how much power that can be used after hours, uh this mainly so our electricity bill doesn't sky rocket during the night if somebody forgot to turn something off somewhere, you know." - Phone Guy describing the power on Night 1
The Power is what the Burger Joint holds to keep everything on. However, there is a disadvantage: The Power has a limit and can only be used when necessary.
This also counts for the Doors, Monitor and Night Vision. If The Penguin gets in, he will go under the desk. Whenever the player uses the cameras, the Penguin will say "Can I take your order?" and randomly open doors, making the player vulnerable to other animatronics, as the Penguin might allow them to enter the Office.
Oddly, the power meter looks more like the flash light battery from FNaF 2 and not the power meter from FNaF 1.
İf player uses night vision all night, they will pass the night (if the player manages to keep Candy and Cindy away) with 1 bar of power. The player can pass all of the nights this way.
When a power outage happens if you are close to 5 am there is a chance you might survive as the power does not shut off immediately.