How it is calculated
Runtime (hours) = battery voltage x Ah x usable fraction x inverter efficiency / load watts. UPS size (VA) = load watts / 0.7 power factor x 1.25 headroom. Lead-acid batteries should not be discharged below about 50% for a long life; lithium LiFePO4 allows about 80%.
Results are estimates for planning. Real systems depend on site conditions; Qyvea surveys and quotes before installation.
Tips from our installers
- Add up every device on the UPS: PC, router, switch, CCTV recorder, printers.
- Never put heavy motors or laser printers on a small UPS.
- Battery runtime falls with age: expect 70 to 80% of the figure after 2 to 3 years.
Frequently asked questions
How long will a 650VA UPS run a router?
A router uses 10 to 20 W, so a small UPS can run it for hours; use the calculator with the UPS battery size.
Is lithium worth the extra cost?
It lasts several times more cycles and gives more usable energy per Ah, so it often wins over 3 to 5 years.
Can I add more batteries?
Only on UPS models built for external batteries; check the manual.
Related
- UPS and power backup in the store
- Solar and power backup solutions
- Best UPS for Wi-Fi router and POS
- All Qyvea calculators
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