The sizing formula
Bank kWh = (load W × hours) ÷ (DoD × efficiency) ÷ 1000, and Ah = bank Wh ÷ system voltage. We use 90% DoD / 95% efficiency for lithium and 50% / 85% for lead-acid — realistic field values, not brochure numbers.
Why 48 V systems dominate
Higher DC voltage means lower current for the same power, which means thinner cables, cooler connections and less line loss. Nearly all modern hybrid inverters above 3 kW are 48 V.
Lithium or lead-acid — which battery is better for solar?
Lithium (LiFePO4) wins on lifetime cost in almost every case: 6,000+ cycles vs 300–500, 90% usable capacity vs 50%, and zero maintenance. Lead-acid only suits very small backup needs on a tight upfront budget.
What does depth of discharge (DoD) mean?
The share of a battery's capacity you can safely use. Draining a lead-acid battery below 50% shortens its life sharply; lithium handles 90–100%.
Why is the bank larger than my backup energy?
Because of DoD and conversion efficiency: to deliver 3.2 kWh from lead-acid at 50% DoD and 85% efficiency, the bank must hold about 7.5 kWh.