Battery Backup Runtime Calculator
Estimate battery-bank runtime, usable watt-hours, DC current, batteries required for a target duration and preliminary battery cost.
Default project preview
1.94 hours
Nominal energy
2.4 kWh
Usable energy
972 Wh
Target batteries
5
Estimated DC current
46.3 A
Calculator
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Methodology
Transparent calculation
BuildMeter converts every input to a consistent internal unit, applies the selected allowance, and rounds products up to whole purchasable units.
Nominal watt-hours = volts × amp-hours × battery count. Usable energy applies depth of discharge, inverter efficiency and reserve. Runtime = usable watt-hours ÷ load watts.
FAQ
Battery Backup Runtime Calculator questions
Why is usable energy lower than nominal energy?+
Battery life limits, inverter losses and a reserve margin reduce the energy available to the AC load.
Does connecting batteries in series increase amp-hours?+
Series connection increases voltage while amp-hours remain the same. Parallel connection increases amp-hours. Bank design must use compatible batteries and protection.
Will motors run from the calculated battery bank?+
Continuous energy is only part of the requirement. Motors and compressors can need much higher startup power from the inverter and battery bank.