About the Solar Battery Calculator
Battery storage size for a solar system, based on evening use and days of autonomy.
Also known as: solar storage size, home battery for solar, off grid battery calculator, battery bank for solar.
How to use this calculator
- Enter daily energy use, share used outside daylight, days of autonomy, usable depth of discharge and the other fields.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
kWh = evening use × days ÷ DoD ÷ round-trip efficiency
Worked example
Using the values pre-filled in the calculator above:
- Daily energy use = 12 kWh
- Share used outside daylight = 60 %
- Days of autonomy = 1
- Usable depth of discharge = 90 %
- Round-trip efficiency = 90 %
- Cost per kWh of storage = 400
the calculator returns:
- Battery capacity needed: 8.889 kWh
- Energy to deliver: 7.2 kWh
- At 48 V: 185.2 Ah
- 5 kWh modules: 2