Solar Battery Autonomy Calculator
Estimate days of autonomy from daily load, usable depth of discharge, and battery bank energy for commercial PV storage planning.
Quick answer
Days ≈ (Bank kWh × DoD × η) ÷ Daily kWh. Example: 40 kWh bank, 0.80 DoD, 0.90 η, 10 kWh/day → 2.9 days. Not UPS runtime. Hub: Solar calculator.
Quick Solar Battery Autonomy Calculator
Defaults: 40 kWh bank · 10 kWh/day · DoD 0.80.
40 × 0.80 × 0.90 ÷ 10.
Advanced Solar Battery Autonomy Calculator
Battery Autonomy Results
Engineering disclaimer
PV/BESS planning estimate only. Do not use UPS runtime or UPS battery calculators for this intent. Confirm chemistry limits, temperature, and OEM usable energy curves before procurement.
Autonomy by bank size
| Bank kWh | Days |
|---|
People also ask
- How do I calculate autonomy days? Usable kWh ÷ daily kWh.
- Same as UPS runtime? No—different domain; do not merge.
- What DoD should I use? Chemistry-dependent; Li often higher than lead-acid.
Planning guidance
- Load first: Build daily kWh in off-grid load.
- BESS depth: See industrial BESS kWh sizing.
- Do not: Link this intent into UPS runtime or UPS battery tools.
- Hub: Solar calculator.
Typical scenarios
- 2-day commercial hybrid: Cover cloudy stretches without full diesel runtime.
- 3-day remote hut: Conservative DoD and winter PSH together.
- Li vs lead: Higher usable DoD shrinks required bank kWh for the same days.
Formula (quick reference)
Days = (Bank kWh × DoD × η) ÷ Daily kWh
Required bank kWh = Daily kWh × Target days ÷ (DoD × η)
Method walkthrough: how to size a solar battery bank (PV autonomy — not UPS runtime).
Frequently Asked Questions
How do I calculate solar battery autonomy days?
Multiply bank kWh by usable DoD and efficiency, then divide by daily kWh load.
How is this different from UPS runtime?
UPS tools estimate minutes of backup for IT/facility UPS systems. This tool estimates multi-day PV storage autonomy—keep the intents separate.
What DoD should I assume?
Follow chemistry and OEM limits—lead-acid often ~0.5–0.8 usable; many Li systems allow higher. Confirm datasheets.
Can I solve for bank size?
Yes—set target days to back-calculate required bank kWh at your DoD and η.
What is the next step?
Review BESS energy guidance, then size MPPT/array for recharge capability.
How it works
Usable energy is nameplate bank kWh reduced by depth-of-discharge and round-trip efficiency. Autonomy days are usable energy divided by daily load. This is not a UPS minute-runtime model.
Worked examples
- 40 kWh · DoD 0.80 · η 0.90 · 10 kWh/day
Usable 28.8 kWh → 2.88 days.
- Target 3 days at same DoD/η
Required bank ≈ 10 × 3 ÷ 0.72 ≈ 41.7 kWh.