How to choose the right line-interactive UPS

Use this buying guide to compare models. Work through the selection criteria in order.

1. Capacity

Add the watts of your devices and choose a UPS with a watt rating at least 25% higher. Check both the VA and the watt rating.

2. Waveform

Pure sine wave output is the safer choice for sensitive electronics, servers, and PCs with active PFC power supplies, since some of these can shut down on a simulated sine wave. Simulated sine wave works for many basic devices and costs less.

3. Runtime and transfer time

Read the runtime chart at your real load. Transfer time is how fast the UPS switches to battery, and it is usually a few milliseconds, which is fast enough for most computers.

4. Outlets

Count the outlets with battery backup and the ones with surge protection only. Check the plug spacing if you use large power adapters.

5. Form factor

Tower models suit desks and floors. Rack models suit server rooms and network closets.

6. Extra features

• LCD display showing load and runtime
• USB or network monitoring for automatic shutdown
• User-replaceable battery
• Automatic voltage regulation (AVR) to correct a brownout

Brands to compare

APC, CyberPower, and Eaton all make solid line-interactive models. Compare the warranty length and whether the battery is covered. Match the model to your setup, such as a home office, a small server, or a network closet.