Vault-Tec reactors require more resources and open space in your settlement, but have the ability to power floors and walls that have a direct connection to it - even without cables. The highest power output from a generator is 10 in the base game, but can go up to 500 with additional options from the “Vault-Tec Workshop” DLC.
Gear (6), Screw (5), Rubber (4), Copper (10), Aluminum (12), Nuclear Material (3) I.e., a Small Generator can only run three lights that require one power each. Little note on the output: You will quickly realize this yourself, but the output number indicates the total amount of power a Generator can produce it does not indicate a type of a device it can support. Small light sources will require as little as 1 power, while larger devices like a water purifier will require 5. The number, meanwhile, indicates the amount of power that is needed for the object to operate. Red color will indicate that the device is unpowered and is not functioning. You will see this information when placing or hovering over them.
All power-dependent objects will display a lightning bolt icon and some will have a number beside it.