UPS Runtime Calculator
Battery capacity:0 Wh
Usable (after efficiency):0 Wh
Estimated runtime:0 min
Equals:0 h 0 min
Estimate only. Real runtime is usually shorter due to the Peukert effect (higher load discharges disproportionately).
How the UPS runtime calculator works
The calculator estimates how long a UPS (uninterruptible power supply) will bridge your devices during an outage. The basis is the energy stored in the batteries in watt-hours, divided by the applied load.
- Battery voltage × capacity: A 12 V battery with 7 Ah stores 84 Wh. Multiple batteries are added up.
- Efficiency: The inverter and cabling cost energy; 85–95% is realistic (default 90%).
- Load (watts): The real active power of the connected devices – not the UPS’s VA rating.
Important: The result is an upper bound. Lead-acid batteries deliver less under high load (Peukert effect), and should not be fully discharged. For critical systems, plan generous reserves.