UPS sizing for PoE networks should begin with the total power required by the switch and all attached powered devices, then add the other equipment that must stay online during an outage.
List every protected device
- PoE switch
- Access points
- Cameras
- Firewall/router
- ISP modem/ONT
- NVR
- Controllers
- Other critical network devices
Calculate PoE load
Add the planning wattage of every powered device. Do not rely only on the current observed idle load.
Use the PoE Budget Calculator for switch-side power planning.
Add the switch and non-PoE load
The switch itself consumes power in addition to the PoE budget delivered to attached devices. Add the firewall, recorder, modem, and other protected loads too.
Choose the required runtime
Decide whether the goal is short ride-through, orderly shutdown, or continued operation through a longer outage.
Estimate runtime
Use the UPS Runtime Calculator to compare battery capacity and connected load.
Leave design headroom
Battery capacity declines with age, and PoE draw can increase when cameras enable infrared illumination or access points operate under heavier load.
Frequently asked questions
Can I size a UPS from VA rating alone?
No. VA and watt ratings describe load capability, while runtime depends on battery capacity and discharge characteristics.
Should the NVR be on the same UPS?
Often it is desirable, but total load and required runtime must be calculated together.
How much aging allowance should I use?
There is no universal value. Battery age, environment, maintenance, and replacement policy matter.