Choosing a UPS for Servers and Offices: Line Interactive vs True Online

A sag, surge or a power cut of a few seconds can shut down a server, corrupt data or damage hardware. A UPS is essential for every system. This guide explains how to pick the right one.

1. UPS types

Type	How it works	Best for
Offline / Standby	Passes mains power through and switches to battery on outage	Desktop PCs and general devices
Line Interactive	Regulates voltage (AVR) during sags and surges, switches quickly to battery	Small servers, switches, NAS, offices
True Online (Double Conversion)	Converts power continuously; clean output with no transfer time	Critical servers, server rooms, non-stop workloads

2. Sizing a UPS (VA and W)

• Add up the watts of everything you will connect, such as servers, switches and storage

• Choose a UPS rated at least 20–30% above that total to allow headroom and longer battery life

• Check both VA and W, e.g. 1500VA/1350W; the W figure is the real power it can deliver

• Servers with active-PFC power supplies should use a UPS with pure sine wave output

3. Runtime and extra batteries

Runtime depends on load: the higher the load, the shorter the runtime. Servers usually need enough time for a graceful shutdown. For longer runtime, choose a model that supports external battery packs (EBM).

4. Features to look for

• Rack / tower – RT models install on the floor or in a rack

• Network management card / SmartConnect – monitor status and shut servers down automatically over the network

• Lithium battery – longer life and lighter than lead-acid

• Hot-swap battery – replace batteries without powering down

5. APC and Eaton ranges we sell

Group	APC	Eaton
Offline / office	Back-UPS	–
Line Interactive	Smart-UPS (SMT / SMC / SMX), Easy UPS	5E, 5PX
True Online	Smart-UPS SRT / SRTG, Easy UPS SRVL	9SX, 9PX

Shop UPS at DC Computer Network

See APC and Eaton models and prices in our UPS category, or send your equipment list via Request a Quote and we will size the UPS and runtime for you.