Solar Panel Calculator
How is the calculation performed?
This calculator determines the number of solar panels needed based on your energy consumption and local conditions:
Number of Panels = (Daily Energy Consumption in kWh × 1000) ÷ (Panel Wattage × Peak Sunlight Hours × System Efficiency)
The result is rounded up to ensure your energy needs are fully met. System efficiency accounts for losses in the inverter, wiring, temperature effects, and other factors that reduce the theoretical maximum output.
Understanding Solar Panel Systems
Factors Affecting Solar Panel Requirements
Several key factors determine how many solar panels you'll need for your specific situation:
- Energy consumption - Your daily or monthly electricity usage in kilowatt-hours (kWh)
- Solar panel efficiency - How effectively panels convert sunlight to electricity (typically 15-22%)
- Panel wattage - The rated power output of each panel (common ranges: 300-500 watts)
- Available sunlight - The average peak sun hours in your location
- Installation angle and direction - Optimal positioning toward the sun
- Shading considerations - Trees, buildings, or other objects that could block sunlight
- Available roof or ground space - Physical limitations of your installation area
Understanding Peak Sun Hours
Peak sun hours refer to the equivalent number of hours per day when solar irradiance averages 1,000 watts per square meter. This is a standardized way to account for varying sunlight intensity throughout the day.
| Geographic Region | Typical Peak Sun Hours |
|---|---|
| Southwest US (AZ, NM, CA, NV) | 5.5 - 7.0 |
| Southeast US (FL, GA, SC, AL) | 4.5 - 5.5 |
| Northeast US (NY, MA, PA, NJ) | 3.5 - 4.5 |
| Northwest US (WA, OR, ID) | 3.0 - 4.0 |
| Midwest US (IL, OH, MI, MN) | 4.0 - 4.5 |
| Central Europe | 2.5 - 3.5 |
| Southern Europe | 4.0 - 5.5 |
| Australia | 4.5 - 6.5 |
System Efficiency Factors
Various factors reduce the theoretical maximum output of a solar system:
| Loss Factor | Typical Range | Description |
|---|---|---|
| Inverter Efficiency | 95-98% | Efficiency of converting DC to AC power |
| Temperature Losses | 5-15% | Panel efficiency decreases as temperature increases |
| Dirt and Dust | 2-5% | Accumulation of debris on panels reduces sunlight absorption |
| Wiring Losses | 1-3% | Resistance in the electrical connections and wiring |
| Panel Degradation | 0.5-1% per year | Gradual reduction in panel efficiency over time |
The default 80% system efficiency in our calculator accounts for these combined losses, but you can adjust this based on your specific circumstances.
Common Solar Panel Sizes and Specifications
Modern residential solar panels typically have these characteristics:
- Wattage: 300-500 watts per panel
- Dimensions: Approximately 65" × 39" (1.65m × 1m)
- Weight: 40-50 pounds (18-23 kg)
- Cell Type: Monocrystalline or Polycrystalline
- Efficiency: 15-22%
- Warranty: 25-30 years
Tips for Solar Panel Installation
- Optimize orientation and tilt - In the Northern Hemisphere, panels should face south; in the Southern Hemisphere, they should face north
- Avoid shading - Even partial shade on one panel can significantly reduce system output
- Consider seasonal variations - Factor in winter months with less sunlight when sizing your system
- Plan for future needs - Consider adding extra capacity if you expect your energy consumption to increase
- Check local regulations - Obtain necessary permits and understand grid connection requirements
- Hire qualified installers - Professional installation ensures safety and optimal performance
Important Considerations
This calculator provides an estimate based on the information you provide. Actual requirements may vary due to:
- Seasonal variations in sunlight and energy consumption
- Local climate conditions and weather patterns
- Specific installation constraints and roof orientation
- Utility regulations and net metering policies
For a precise evaluation, consider consulting with a professional solar installer who can perform a site-specific assessment.