It would be helpful to know OP’s use case for the UPS. Just need enough time to save your game/work? Want to keep your modem and router running so you can have wifi while the power is out?
Something to keep in mind is, without a massive battery and a very expensive UPS, you won’t be gaming in the dark for very long. Maybe 15 minutes max with most consumer-grade UPS. Even commercial-grade UPS only stay on long enough to gracefully shut down services. For anything more, a generator is best.