Solar Panel Charge Time Calculator
Estimate hours or peak-sun-days to recharge a battery bank from PV array power and peak sun hours.
Quick answer
Charge days (PSH) ≈ Battery Wh ÷ (Array W × PSH × η). Example: 10,000 Wh, 2000 W array, 5 PSH, η 0.8 → ~1.25 sun-days. Hub: Solar calculator.
Quick Charge Time Calculator
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Charge Time Results
Engineering disclaimer
Planning estimate only. Assumes constant effective charge power during PSH—clouds and MPPT limits change real time. Not UPS runtime.
Sun-days by array W
| Array W | Sun-days |
|---|
People also ask
- How long to charge? Wh ÷ (W×PSH×η).
- Clock hours? Roughly sun-days × daylight—not exact.
- UPS? Different intent—do not merge.
Planning guidance
- Get PSH from peak sun hours.
- Autonomy context: battery autonomy days.
- Hub: Solar calculator.
Typical scenarios
- Overnight discharge: Restore usable Wh before next night.
- Multi-day recovery: After autonomy event, size array so recharge < 1–2 sun-days.
- Partial DoD: Only restore depleted Wh, not full bank.
Formula (quick reference)
Sun-days = Battery Wh ÷ (Array W × PSH × η)
Approx clock hours ≈ sun-days × 24 (coarse).
Bank sizing method: how to size a solar battery bank (PV autonomy — not UPS).
Frequently Asked Questions
How do I calculate solar panel charge time?
Divide the watt-hours to restore by array watts × peak sun hours × charge-path efficiency.
Is this the same as UPS charge time?
No—this is PV→battery recharge under solar resource assumptions, not UPS charger runtime.
What efficiency should I use?
Often 0.75–0.85 including MPPT and battery acceptance—confirm OEM data.
What if weather is cloudy?
Effective PSH drops—use conservative PSH or expect longer recovery.
What is the next step?
If recharge is too slow, increase array kW in panel sizing or reduce autonomy depth.
How it works
Daily PV energy available for charging is array watts × PSH × efficiency. Dividing depleted Wh by that energy yields peak-sun-days to recover.