Battery Capacity Calculator
Use this battery capacity workflow for early backup-runtime planning. It does not choose a battery chemistry, BMS, inverter, or listed energy-storage system.
- Load energy
- Wh
- Required battery capacity
- Wh
- Required battery capacity
- kWh
- Required battery capacity
- Ah
Calculation details
- Usable factor
- x
- Calculation basis
- Selection boundary
Recent results
Formulas
- Load energy Wh = load watts x runtime hours
- Usable factor = depth of discharge percent / 100 x efficiency percent / 100
- Required battery Wh = load energy Wh / usable factor
- Required battery Ah = required battery Wh / system voltage
Use this calculator
Estimate required battery Wh, kWh, and Ah from load, runtime, voltage, usable 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 capacity estimate uses entered runtime assumptions only. It does not approve battery chemistry, BMS, enclosure, inverter, protection, ventilation, fire-safety, utility, or code compliance.
FAQs
Does this choose a battery?
No. It estimates capacity from entered runtime assumptions. Chemistry, BMS, temperature, discharge rate, and listing data require separate review.
Why adjust for depth of discharge?
Many systems are planned around usable capacity rather than draining the entire nominal battery capacity.