Power

Power is a resource in Fallout Shelter.

Overview
Power is a critical strategic resource, allowing you to power and use the rooms within your Vault. Without sufficient levels of power, such as when the power level is in the red, other rooms will cannot function as they are not receiving the power they require. If the diner or water treatment room are unpowered, you are facing a crisis, as that means your dwellers will start starving and suffering from irradiation.

As a result, if in doubt, always, always prioritize power over everything else.

Generating power
There are two basic sources of power:
 * Power generator rooms, available from the start.
 * Nuclear reactors, which provide lots of power in the late game.