how much wattage output a UPS should have in the event of a blackout?

Answer 1

Depends on what you plan to run on your UPS. Just make sure that the rated wattage of your UPS is more than the total wattage of the equipment attached to it.

From a practical standpoint, only attach those items that are considered critical, such as your computer's CPU and monitor so you can finish what you're working on and then shut down safely, or cordless phone systems and VoIP adaptors so that you don't lose your phone service.