Why this answer matters
Sizing a UPS from 1500VA alone can overload it when the connected equipment approaches or exceeds 900W.
2 requirements3 verification steps1 primary source
Requirements
What has to be true
- Keep the combined real load within the UPS's 900W rating and leave practical headroom for transients/runtime goals.
- Connect critical equipment to battery-backed outlets, not surge-only outlets.
Verify it yourself
Use this test sequence
Change one variable at a time so you know which requirement made the difference.
- 1
Add the realistic watt draw of the devices that must stay online.
- 2
Use the DeviceOK backup-power sizing calculator with measured/credible loads.
- 3
Run APC's native self-test/management workflow for battery and hardware state.
Limits
What this answer does not prove
- Runtime depends strongly on actual load and battery condition.
- A browser calculator cannot certify battery health or UPS fault state.
Relevant DeviceOK checks