Off-Grid Battery Bank Amp-Hour Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 28, 2026Off-Grid Battery Bank Amp-Hour Calculator
Sizing a battery bank for an off-grid solar system? This calculator accounts for daily energy needs, backup autonomy, and safe depth of discharge.
Required Ah = (Daily Energy Needed x Days of Autonomy) / (Depth of Discharge x System Voltage)
Example
3,000 Wh daily need, 24V system, 2 days autonomy, 50% depth of discharge:
Total Wh Needed = 6,000 → ~500 Ah battery bank needed
Why Depth of Discharge Matters So Much
Depth of discharge (DoD) is factored in because regularly discharging most battery chemistries beyond their rated DoD - commonly 50% for lead-acid batteries, considerably higher for lithium - significantly shortens battery lifespan, meaning the true safely usable capacity is well below the battery's full rated capacity.
Days of Autonomy Protects Against Cloudy Stretches
Sizing for 2 or more days of autonomy (rather than exactly one day of need) provides a buffer against multi-day cloudy or low-wind stretches when solar or wind charging input is reduced, avoiding a full system outage during extended poor-weather periods.