UPS Runtime Calculator
Estimate approximate runtime from UPS battery capacity, inverter efficiency, connected load, and battery aging allowance.
This is a simplified planning model. Real UPS runtime depends on battery chemistry, discharge curve, temperature, battery health, inverter design, UPS firmware, and manufacturer-specific runtime characteristics.
Use the PoE Budget Calculator to estimate the switch power required for access points, cameras, phones, and other PoE devices.
Open PoE Budget Calculator →How this UPS runtime calculator works
The calculator estimates nominal battery watt-hours from voltage and amp-hours, then reduces that value for inverter efficiency, usable battery capacity, and battery aging before dividing by the connected load.
Worked example
A 24 V, 18 Ah battery system has 432 nominal watt-hours. After efficiency, usable-capacity, and aging allowances, the usable energy may be much lower. A 250 W load therefore has substantially less runtime than a simple 432 ÷ 250 calculation suggests.
Why actual runtime varies
Battery chemistry, discharge curve, temperature, battery age, load level, UPS firmware, and inverter design all influence real runtime.