Solar Battery Bank Calculator
Size an off-grid battery bank from daily energy, autonomy days, usable depth of discharge, efficiency and voltage.
Size an off-grid battery bank from daily energy, autonomy days, usable depth of discharge, efficiency and voltage.
Size an off-grid battery bank from daily energy, autonomy days, usable depth of discharge, efficiency and voltage.
Enter your own equipment values. The calculator uses transparent assumptions so you can adjust efficiency, reserve and operating conditions.
Use Real Equipment Ratings
Size an off-grid battery bank from daily energy, autonomy days, usable depth of discharge, efficiency and voltage.
Calculator Guidance
Use the result for planning, then verify the exact product manual, nameplate ratings and operating limits.
Solar Battery Bank Calculator
Planning estimate only.
Formula
Bank Wh = daily AC Wh × autonomy days ÷ inverter efficiency ÷ usable depth of discharge.
Examples
| Daily Load | Autonomy | DoD/Efficiency | Bank Energy |
|---|---|---|---|
| 1000Wh | 2 days | 90% / 90% | 2469Wh |
| 3000Wh | 2 days | 90% / 90% | 7407Wh |
| 5000Wh | 3 days | 80% / 90% | 20,833Wh |
Bank Design Limits
Peak Power
Energy sizing does not confirm inverter current.
Parallel Strings
Require matched wiring.
Temperature
Affects usable capacity.
Charging Window
Solar array must refill bank.
Reserve
Critical systems need margin.
Code Compliance
Large battery installations require professional design.
How to Use the Result in the Real World
Treat the calculated result as a planning baseline rather than an exact promise. Real systems lose energy through conversion, wiring, temperature effects and internal electronics, while appliances can draw differently from their nameplate ratings.
Leave practical headroom instead of selecting equipment that exactly matches the result. Extra margin helps with startup surges, battery aging, changing weather and future loads, and it reduces the chance that normal variation pushes the system beyond its limits.
When the result affects a major purchase, verify the important inputs. Measure appliance consumption when possible, check the exact inverter or charge-controller limits, and compare the calculation with the equipment manufacturer's specifications.
Frequently Asked Questions
How many autonomy days should I use?
One to three days is common depending on climate and backup strategy.
Should AC losses be included?
Yes.
Why use 48V?
It reduces current in larger systems.
Does this size solar panels too?
No.
Can batteries be mixed?
Avoid mixing different ages, chemistries or capacities.
Do home systems need permits?
Often yes.