Solar Battery Calculator

Calculate the battery capacity needed to store solar energy for backup use.

Calculate

Enter your values below.

e.g. 0.5 means only using half the battery's capacity

Result

Required battery capacity
0

Formula used

Capacity (Ah) = (Daily energy × Days of autonomy) ÷ (Voltage × Depth of discharge)

Example: 5,000 Wh/day, 48V bank, 2 days autonomy, 50% DoD → capacity ≈ 417 Ah.

How to use this calculator

  1. Enter Daily energy need (Wh), Battery bank voltage (V), Days of autonomy needed, Depth of discharge (0-1).
  2. Press Calculate to see your result instantly.

FAQ

Frequently asked questions

What is 'depth of discharge'?

The percentage of a battery's capacity that's safely usable — many batteries shouldn't be fully drained to preserve lifespan.

What is 'days of autonomy'?

How many days you want the battery bank to supply power without any solar input (e.g. during cloudy weather).

Why does a lower depth of discharge require a bigger battery?

Because you're only using a smaller fraction of its total capacity, so more total capacity is needed to supply the same usable energy.

Does battery chemistry affect the recommended depth of discharge?

Yes — lithium batteries often tolerate deeper discharge than lead-acid batteries.