The three numbers that matter
Battery sizing comes down to three figures: your daily energy use (Wh), the days of autonomy you want, and the battery's usable depth of discharge (DoD).
Multiply daily Wh × autonomy days ÷ DoD to get the minimum bank capacity. For lithium batteries, use 0.9 DoD; for lead-acid, use 0.5.
A worked example
A Nigerian home using 3,000 Wh/day that wants 1.5 days of autonomy with lithium storage needs: 3,000 × 1.5 ÷ 0.9 = 5,000 Wh, or 5 kWh of usable battery capacity.
Round up to the nearest standard module size, and confirm your installer sizes the inverter to handle surge loads from pumps or fridges.
Frequently asked questions
battery storage sizing residential technology
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