ToolnozaELECTRICAL TOOL
UPS Runtime Calculator
Estimate UPS battery backup hours and minutes from battery voltage, amp-hours, count, usable capacity, efficiency and load.
UPS Runtime Calculator
FREE ONLINE TOOLSTEP BY STEP
How to use ups runtime calculator
- Compare your result with the worked example.
- Check the assumptions and limitations.
WHEN IT HELPS
Common uses
- Estimate battery-backed runtime under a stable power draw. Use manufacturer data for actual battery discharge performance.
Method and assumptions
Usable Wh = battery V × Ah × battery count × usable fraction × conversion efficiency. Runtime (h) = usable Wh / AC load W.
Worked example
Two 12 V, 100 Ah batteries at 70% usable energy and 85% efficiency deliver 1,428 Wh. At 300 W the estimate is 4.76 h.
Limitations
Assumes equivalent batteries whose nominal watt-hours are additive. High discharge rates, aging, cutoff, UPS standby draw and temperature reduce runtime. Always verify DC architecture and supplier charts.
Frequently asked question
Why is actual UPS runtime shorter?
Discharge-rate losses, battery condition, inverter losses and cutoff voltages can reduce usable energy.