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Insights· 8 October 2026 · 1 min read

Sizing backup power for a network room

A UPS bridges an outage; it does not replace a generator. How to estimate what you need and what to avoid.

Racks of servers with blue indicator lights

Photo: Pexels

When power drops, the network goes with it, and so do phones, cameras and access control. A UPS (uninterruptible power supply) keeps critical equipment running through short outages and gives it time to shut down cleanly in longer ones.

Start from the load

List the equipment that must stay up: switches, routers, servers, access points, phone systems. Add up their power draw, in watts, from the datasheets or a measurement.

Decide the runtime

Ask how long the equipment must run: a few minutes to shut down cleanly, or longer to ride out brief outages. Runtime depends on battery capacity relative to the load.

Leave margin

  • Do not size the UPS at 100% of today's load: equipment grows.
  • Account for the power factor when comparing watts and volt-amperes.
  • Plan for battery ageing: capacity falls over the years, and batteries need replacing.

Pairing with the rest of the site

A UPS protects against more than outages: it also conditions power against surges. For sites with longer outages, it works with a generator or other energy equipment rather than replacing it.

Energy and backup power equipment is one of the five product families in the EnnovaMarket catalogue.