How to Size a UPS for a NAS

1. Measure the complete protected load

Include the NAS, required network path, and any device that must stay powered long enough to communicate or shut down. A power-supply rating is not a load measurement.

2. Add operating headroom

Allow for startup behavior, future drives, and conversion losses. Keep the estimated load below both the UPS watt and VA ratings.

3. Set a shutdown objective

Decide how many minutes are needed to ride through a short interruption or complete an orderly shutdown. Indefinite operation is not the normal NAS objective.

4. Verify the runtime curve

Battery runtime is nonlinear and model-specific. Compare the expected watt load with the manufacturer curve; VA alone cannot establish runtime.

5. Test the procedure

• Connect data communication and configure shutdown thresholds.
• Test notification and shutdown without risking production data.
• Record battery replacement and self-test procedures.
• Keep backup copies independent of the UPS-protected system.