Solar Array Sizing Calculator
Determine the solar panel wattage needed to meet your energy needs based on your location's sun hours and system efficiency.
How many solar panels do you actually need? The answer depends on three things: your daily energy usage (kWh), your location's peak sun hours, and real-world system losses. This solar panel size calculator uses the formula: Array Watts = Daily kWh / (Sun Hours x Efficiency). Enter your average daily usage from your utility bill, select your region, and the tool calculates total wattage needed and the number of panels to meet your production goals.
Don't know your daily usage? Check your electric bill for the monthly kWh total and divide by 30. For off-grid systems, use our off-grid load calculator to estimate Wh/day from individual appliances.
Daily Energy Usage
Check your utility bill for average daily kWh usage
Quick reference (US averages):
Location & Sun Hours
System Efficiency
Accounts for inverter efficiency, wiring, temperature, and soiling
Results
Enter your usage and location to see results
Understanding Array Sizing
Peak Sun Hours
Peak sun hours represent the equivalent number of hours at 1,000 W/m² solar irradiance. This varies significantly by location and season.
System Losses
Real-world systems lose 15-25% of rated output due to inverter efficiency, wiring, temperature derating, soiling, and shading.
Oversizing
Many installers oversize by 10-20% to account for panel degradation and ensure production meets expectations year-round.
Net Metering
If your utility offers net metering, consider sizing to 100-110% of annual usage to maximize bill credits during sunny months.
Need a detailed site assessment?
Our team can help with shading analysis and optimized system design.