Live Demo — Solar Panel Power Calculator
Enter your daily energy consumption and local solar resources to get the required panel wattage instantly.
Solar Panel Power Calculator
Free professional solar panel sizing calculator for off-grid solar lighting systems. Input your daily load, local peak sun hours and system efficiencies to determine the required photovoltaic panel power, apply a safety factor, and verify energy generation even in the worst month of the year.
Key Features
Load Parameters
Set daily power consumption, peak power and system operating voltage (12V / 24V / 48V) to describe your total load demand.
Local Solar Resources
Input average daily peak sun hours, worst-month sunshine hours and installation latitude for accurate resource assessment.
System Efficiency
Account for solar panel efficiency loss, charge controller efficiency (MPPT/PWM) and DC cable loss in one combined system efficiency.
Safety Factor
Apply an adjustable safety factor (1.0-1.5) that covers weather variability before recommending the final panel wattage.
Panel Recommendation
Automatically round up to the nearest common panel specification (50W, 100W, 150W, 200W ...) for easy procurement.
Worst-Month Verification
Check whether the recommended panel still covers daily demand using worst-month sunshine hours, and get a clear pass/fail status.
Technical Specifications
| Platform | HTML5 Web App | Android (via WebView) |
| Core Calculation | P_pv = P_daily / (H × η_total), then × safety factor |
| System Voltage | 12V / 24V / 48V |
| Peak Sun Hours | 2 - 8 h/day (normal + worst-month) |
| Panel Efficiency Input | 10% - 30% loss (temperature, dust, aging) |
| Controller Efficiency | 80% - 98% (MPPT / PWM) |
| Safety Factor | 1.0 - 1.5 (weather variability) |
| Recommended Specs | 10W - 500W standard panels |
| Industry Standards | IEC 61215, IEC 62548, AS/NZS 4509.2, IEC 61724-1 |
| Output | Recommended panel wattage + worst-month supply status |
Frequently Asked Questions
How is the required solar panel power calculated?
The calculator divides your total daily energy consumption by the product of peak sun hours and total system efficiency (P_pv = P_daily / (H × η_total)), then multiplies by a safety factor to cover weather variability. The result is rounded up to the nearest common panel specification.
What are peak sun hours (PSH)?
Peak sun hours is the number of hours per day (h/day) during which solar irradiance equals a standard 1,000 W/m². A location with 4.5 PSH receives the same total daily energy as 4.5 hours of full sun, regardless of the actual daylight duration.
Why check the worst-month sunshine hours?
The worst-month verification ensures the recommended panel still generates enough energy during the least sunny month of the year (typical winter/rainy season). This prevents under-sizing that would otherwise leave the lighting system short of power on cloudy streaks.
What efficiency losses are included?
The calculator combines solar panel efficiency loss (temperature, dust and aging, typically 15-25%), charge controller efficiency (MPPT/PWM, typically 85-95%) and DC cable loss (typically 3-5%) into a single total system efficiency used in the sizing formula.
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