Battery Runtime Calculator
Use this battery runtime workflow for a quick backup-time estimate from entered battery and load assumptions.
- Nominal battery energy
- Wh
- Usable battery energy
- Wh
- Estimated runtime
- h
- Usable factor
- x
Calculation details
- Calculation basis
- Selection boundary
Recent results
Formulas
- Nominal Wh = battery Ah x system voltage
- Usable Wh = nominal Wh x depth of discharge percent / 100 x efficiency percent / 100
- Runtime hours = usable Wh / load watts
Use this calculator
Estimate usable battery energy and runtime from Ah, voltage, load, depth of discharge, and efficiency.
Read the result
Review the calculated values with their displayed units and assumptions. The result is a planning aid for the stated inputs, not a final equipment or installation decision.
Check before final work
This battery runtime estimate uses entered battery and load assumptions only. It does not approve battery chemistry, inverter, BMS, protection, fire-safety, utility, or code compliance.
FAQs
Why is runtime only an estimate?
Actual runtime changes with battery chemistry, age, temperature, discharge rate, inverter efficiency, and cutoff settings.
Can I use Wh instead of Ah?
This calculator takes Ah and voltage, then converts to Wh. Use the Battery Capacity Calculator when planning from load and desired runtime.