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Calculating autonomy and battery capacity
Calculation4 min readUpdated: 2025-06
Autonomy represents the number of days the system can power loads without solar production (bad weather, cloudy periods). In West Africa, 1–2 days is generally sufficient. In remote rural areas, 3 days may be justified.
C_Ah = (E_Wh/day × autonomy_days) ÷ (V_sys × DoD)Fundamental formula — all other parameters derive from it
3,450 Wh
Daily consumption
90 Ah
1 day (LiFePO4 48V)
4.3 kWh
180 Ah
2 days (LiFePO4 48V)
8.6 kWh
270 Ah
3 days (LiFePO4 48V)
12.9 kWh
For a hybrid system (panels + grid), 1 day autonomy is sufficient as the grid takes over. For off-grid in rural areas with rainy season, plan for 2–3 days.
Common mistakes
- Defaulting to 3 days autonomy "to be safe" on a hybrid system with a reliable grid
- Confusing autonomy (days without sun) with total battery capacity
- Not adjusting autonomy for the rainy season in affected regions