Home Battery Backup Runtime Calculator accuracy and testing

Formula source

• Runtime hours = battery kWh * depth of discharge percent * inverter efficiency percent / average load kW.

Test cases

Known limitations

• This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
• Use the result as a planning estimate unless the calculator page states a stricter purpose.

Assumptions

• Average load is steady across the backup window.
• Solar recharge during the outage is not included unless you reduce average load or add capacity manually.
• Calculations run locally and are for planning only.

Unit handling

• Battery Capacity accepts values in kWh.
• Usable Depth of Discharge accepts values in %.
• Inverter Efficiency accepts values in %.
• Average Load accepts values in W.
• Runtime is displayed in hours.
• Usable Energy is displayed in kWh.
• Average Load is displayed in kW.

Rounding rules

• Number displays use up to 2 decimal places in the calculator UI.
• Input precision follows configured step values where provided.

Version history

Change log