Online vs line-interactive UPS: which to choose

The two most common UPS topologies are line-interactive and online (double conversion). They differ in how they protect the load and what they cost to run.

Line-interactive

A line-interactive UPS passes mains power through and corrects voltage with an automatic voltage regulator (AVR). It switches to battery only on an outage, with a brief transfer time. It is efficient and affordable — a good fit for PCs and workstations.

Online (double conversion)

An online UPS converts incoming AC to DC and back to AC continuously, so the load always runs from the inverter. There is no transfer time and the output is a clean sine wave, fully isolated from mains problems. This suits servers, storage and data centres.

How to decide

For desktops and non-critical loads, line-interactive is usually enough. For servers, network cores and anything that must not blink, choose online. See the sizing guide for power and runtime.