Decide what needs battery power
List the equipment that must stay on during a short outage. A desktop computer and its monitor need a different plan from a laptop with its own charged battery. Include the router and modem if keeping your local connection running is part of the goal.
Write a simple outcome next to each device: save a document, finish a shutdown, or keep local network equipment powered. This avoids sizing backup for every accessory on the desk. A powered router alone does not guarantee internet access if the provider’s equipment is unavailable.
Check the outlet labels on the UPS. Some outlets may provide surge protection without battery backup. Put the devices that need continued power on the battery-backed outlets, within the manual’s limits.
Compare capacity and runtime separately
UPS specifications include watt and volt-ampere (VA) ratings. These are different limits, and both matter. Add up the equipment you intend to support, allow for changing loads, and use the manufacturer’s sizing guidance. Do not treat a large VA number as a promise of long runtime.
Check the manufacturer’s runtime chart at the load you expect to connect. More connected equipment generally reduces available battery time. Ask how much time you actually need, then compare models at that load rather than comparing only their headline capacity.
- Confirm the US voltage and outlet type suit your equipment.
- Check both capacity limits and the runtime at your expected load.
- Verify that the output waveform meets your computer power supply’s requirements.
For compatible plug-in equipment, our guide to measuring appliance power helps you understand the load before using a manufacturer’s UPS sizing tool.
Plan the shutdown and the upkeep
If the computer may be unattended, check for compatible automatic-shutdown software and the required connection. Follow the setup instructions so the computer can shut down before the battery runs out. A battery on the floor is only part of the plan.
Read the instructions for ventilation, battery checks and replacement. Include replacement-battery availability in your comparison. Follow the manufacturer’s test procedure after setup, and keep a record of warnings or battery-test results.
ENERGY STAR’s product finder can help you compare certified efficient UPS models. Efficiency reduces losses relative to a less efficient UPS; it is not a claim that adding backup uses less electricity than having no UPS. Our launch guide explains the buying decisions and does not rank or claim to have tested individual models.
Compare specific capacities and features in our home-office UPS buying guide.