Solar Battery Sizing Calculator
Calculate the battery bank capacity needed for your solar system.
Enter daily energy usage, days of autonomy, and battery voltage for accurate Ah sizing.
Battery Bank Size
Solar battery bank sizing ensures you have enough stored energy to cover your usage during cloudy days or nighttime.
Formula:
Total Wh = Daily kWh x 1000 x Days of Autonomy
Required Ah = Total Wh / Battery Voltage / Depth of Discharge
Depth of Discharge (DoD) guidelines:
- Lead-acid (flooded): 50% DoD (never discharge below 50%)
- AGM: 50% DoD
- Lithium (LiFePO4): 80% DoD
- Lithium-ion: 80–90% DoD
Example:
- Daily usage: 5 kWh
- Days of autonomy: 2
- Battery voltage: 48V
- Battery type: LiFePO4 (80% DoD)
- Required: (5000 x 2) / 48 / 0.8 = 260 Ah
Battery voltage options:
- 12V — Small systems, RVs, boats
- 24V — Medium residential systems
- 48V — Large residential, most common for off-grid
Sizing tips:
- Add 10–20% extra for system losses (inverter, wiring)
- More days of autonomy = larger bank but less stress per cycle
- Lithium batteries cost more upfront but last 3–5x longer than lead-acid