[zrm]

A small UPS will often have the equipment running directly on AC input power and only switch to the battery if the input power fails.

[smolder]

Oh, thanks for the correction. It seems I forgot that type existed or just never knew. Now I'm curious about the relative merits. I'd guess the transition is not as smooth and presents some kind of a risk that's unacceptable for critical infra.

[agapon]

The terms that describe those types are Line-interactive and On-line UPS.

E.g., https://blog.tripplite.com/line-interactive-vs-on-line-ups-s...