Battery Bank Size Calculator
Fill in the values and the answer updates as you type.
How the Battery Bank Size Calculator works
Capacity (Wh) = daily use × days of autonomy ÷ depth of discharge ÷ efficiency. Dividing by system voltage gives amp-hours. The battery count assumes 12V 100Ah units wired in series for higher voltages and in parallel for more capacity. Example: with the default values, battery capacity needed comes to 1,111 Ah.
Inputs and results
The Battery Bank Size Calculator takes 5 inputs and gives 3 results.
What you enter
- Daily energy use (Wh) — starts at 3000.
- Days of autonomy — starts at 2.
- Depth of discharge (%) — starts at 50.
- System voltage (V) — starts at 12. Choose from: 12, 24 and 48.
- System efficiency (%) — starts at 90.
What you get
- Battery capacity needed (Ah)
- Energy capacity needed (Wh)
- 12V 100Ah batteries needed
Example: Battery Bank Size Calculator with the starting values
With daily energy use 3000 Wh, days of autonomy 2, depth of discharge 50 %, system voltage 12 V and system efficiency 90 %, the calculator returns:
| Battery capacity needed (Ah) | 1,111 |
|---|---|
| Energy capacity needed (Wh) | 13,333 |
| 12V 100Ah batteries needed | 12 |
Change any value above and the results update straight away.
Battery Bank Size Calculator FAQ
How do I use the Battery Bank Size Calculator?
Enter daily energy use, days of autonomy, depth of discharge and system voltage in the fields, then read battery capacity needed (ah), energy capacity needed (wh) and 12v 100ah batteries needed in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the Battery Bank Size Calculator calculate?
Size a battery bank for off-grid or backup power. It returns battery capacity needed (ah), energy capacity needed (wh) and 12v 100ah batteries needed from the 5 values you provide.
What values does the Battery Bank Size Calculator start with?
It opens with daily energy use 3000 Wh, days of autonomy 2, depth of discharge 50 % and system voltage 12 V so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the Battery Bank Size Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the Battery Bank Size Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.