Buying a UPS without knowing your load is like buying shoes without knowing your size. Here is a simple way to work out the UPS kVA you need.
Step 1 – List every device the UPS will power
Note each device's wattage from its nameplate or datasheet. If only amps are given: Watts = Volts × Amps (use 230V for single-phase).
Step 2 – Add them up
Example small server room:
• 2 servers × 450 W = 900 W
• 2 network switches × 60 W = 120 W
• 1 firewall/router × 50 W = 50 W
• 1 NVR + monitor × 150 W = 150 W
Total load = 1, 220 W
Step 3 – Convert watts to kVA
kVA = Watts ÷ (Power factor × 1000)
• UPS with unity power factor (1.0), like the Liebert ITA2: 1, 220 ÷ 1, 000 = 1.22 kVA
• UPS with 0.8 power factor: 1, 220 ÷ 800 = 1.53 kVA
Step 4 – Add headroom
Size the UPS so your load is about 70–80% of its rating. 1.22 kW ÷ 0.75 ≈ 1.6 kW, so a 2kVA unity-PF UPS is the right choice.
Step 5 – Decide backup time
Backup time depends on the battery bank (Ah and number of batteries), not the kVA rating. Tell us how many minutes or hours you need and we will size the batteries.
Common mistakes:
• Ignoring the inrush current of motors, compressors and laser printers
• Treating kVA and kW as equal on UPS with a power factor below 1
• Running a UPS at 100% load, which shortens battery and component life
Not sure of your load? APS engineers can measure it and recommend the right model.
📞 Call +91 99489 10784 / +91 99483 72888 · ✉️ info@apstechsystems.com · or tap Enquire Now
#UPSSizing #kVA #PowerBackup
Step 1 – List every device the UPS will power
Note each device's wattage from its nameplate or datasheet. If only amps are given: Watts = Volts × Amps (use 230V for single-phase).
Step 2 – Add them up
Example small server room:
• 2 servers × 450 W = 900 W
• 2 network switches × 60 W = 120 W
• 1 firewall/router × 50 W = 50 W
• 1 NVR + monitor × 150 W = 150 W
Total load = 1, 220 W
Step 3 – Convert watts to kVA
kVA = Watts ÷ (Power factor × 1000)
• UPS with unity power factor (1.0), like the Liebert ITA2: 1, 220 ÷ 1, 000 = 1.22 kVA
• UPS with 0.8 power factor: 1, 220 ÷ 800 = 1.53 kVA
Step 4 – Add headroom
Size the UPS so your load is about 70–80% of its rating. 1.22 kW ÷ 0.75 ≈ 1.6 kW, so a 2kVA unity-PF UPS is the right choice.
Step 5 – Decide backup time
Backup time depends on the battery bank (Ah and number of batteries), not the kVA rating. Tell us how many minutes or hours you need and we will size the batteries.
Common mistakes:
• Ignoring the inrush current of motors, compressors and laser printers
• Treating kVA and kW as equal on UPS with a power factor below 1
• Running a UPS at 100% load, which shortens battery and component life
Not sure of your load? APS engineers can measure it and recommend the right model.
📞 Call +91 99489 10784 / +91 99483 72888 · ✉️ info@apstechsystems.com · or tap Enquire Now
#UPSSizing #kVA #PowerBackup
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