Solar Panel Calculator
Enter your daily energy usage, panel wattage, average sun hours, and system efficiency to estimate the panels needed.
How solar panel quantity is estimated
This calculator converts your daily energy usage to watt-hours, then divides it by how much energy a single panel produces in a day — the panel's wattage multiplied by your location's average peak sun hours and an efficiency factor that accounts for inverter losses, wiring losses, dust, and temperature effects.
Peak sun hours aren't the same as daylight hours — they represent the equivalent number of hours of maximum sunlight intensity your location receives, which varies significantly by latitude, season, and local climate.
Frequently asked questions
Why isn't the system efficiency 100%?
Real solar systems lose some energy to inverter conversion losses, wiring resistance, panel temperature effects, dust and dirt accumulation, and panel degradation over time. 75-85% overall system efficiency is a typical realistic range.
How do I find my local average sun hours?
Peak sun hour data is available from government solar resource maps or online solar irradiance calculators for your specific location — it varies substantially by region and season, so use your location's seasonal or annual average for a realistic estimate.
Does this account for cloudy days or seasonal variation?
Using an annual average sun-hour figure smooths out day-to-day and seasonal variation. For a system that must reliably cover your usage even in winter or during cloudy stretches, consider sizing based on your location's worst-case season instead of the annual average.