SOLAR · CALCULATOR

Solar battery capacity calculator

Free solar battery capacity calculator: get nominal battery capacity from daily energy, autonomy, usable depth of discharge, efficiency and voltage.

Written by Chameera Sampath · Not yet reviewed by a licensed electrician. See the methodology.

US (NEC) only · NFPA 70 / NEC — locally adopted editionDefaults are US values. Verify the locally adopted NEC edition and project data.Official reference ↗

Project inputs

Measurements

Daily energy

kWh

Autonomy

days

Usable depth of discharge

Efficiency

Voltage

Updates as inputs change. Unit changes preserve the same physical values.

THE MATH BEHIND THE ANSWER

Method & assumptions

Capacity = energy × days / (DoD × η); Ah = Wh / V

Energy sizing only; power, surge, BMS, temperature and aging require separate checks.

Results do not check every aspect of an electrical installation. The calculators follow US (NEC) practice only; a regional preset changes defaults such as voltage and units, and no result certifies NEC compliance.

Sources and validation →

Worked example

Daily energy: 5 kWh · Autonomy: 2 days · Usable depth of discharge: 80 % · Efficiency: 90 % · Voltage: 48 V

Nominal battery capacity: 13.889 kWh · Nominal capacity: 289.352 Ah

This example uses the stated inputs; results for the entered values appear above.

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Estimating and invoicing tool

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