Energy & Electrical
Solar Lighting Runtime Calculator
Size solar panels and batteries for off-grid and solar-powered lighting systems. Enter load, peak sun hours, and battery specs to find panel wattage and runtime.
Lighting Load
Light Wattage  20 W
Hours ON per night  8 hrs
Number of Fixtures  1
Solar & Battery
Peak Sun Hours (PSH)  4.5 hrs/day
Location / Climate
Battery Voltage  12 V
Autonomy Days  3 days
System Efficiency  85%
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Wh/day
Daily load
—
W panel
Min panel size
—
Ah battery
Min capacity
—
nights
Autonomy
System Sizing Breakdown
Total load per night—
Daily Wh needed (with efficiency loss)—
Required panel output (Wh ÷ PSH)—
Battery capacity needed (Wh ÷ V × days)—
Recommended panel (25% safety margin)—
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The calculators and tools on LightingCalc.lighting are provided for general guidance and informational purposes only. Results are estimates based on standard formulas and the values you enter — they do not constitute professional engineering, electrical, or architectural advice. Always verify calculations with a qualified professional before making decisions for any safety-critical, code-compliance, or commercial application. LightingCalc.lighting makes no representations or warranties as to the accuracy or completeness of any result, and accepts no liability for errors, omissions, or any outcomes arising from reliance on this information.