Peak Sun Hours
Understanding Peak Sun Hours
I get asked all the time, “How much solar energy can I expect to produce in my area?” and “How sunny is my area?”
We answer that question with Peak Sun Hours. Peak Sun Hours is the technical term we use to describe the amount of sunlight a location receives. It’s not just the number of hours between sunrise and sunset, but it takes into account cloud cover, weather patterns, and more.
The super technical definition is that it’s the number of hours of sunlight at 1,000 watts per square meter (1 kW/m²) – the standard testing condition for rating solar panels.
Throughout the day, sunlight intensity varies dramatically. Early morning and late evening provide lower intensity (200-500 W/m²), while midday can exceed 1,000 W/m² in ideal conditions. Peak sun hours aggregate all this varying sunlight into equivalent hours at peak intensity. For example, receiving 500 W/m² for 2 hours equals 1 peak sun hour (500 × 2 = 1,000).
Of course, sunlight varies dramatically by time of year and location. You’ll really enjoy using our interactive tool below to see how your region compares to others. For example, Phoenix, Arizona produces 35% more solar energy than Chicago, Illinois.
How to Read This Data: The grid below shows the total solar energy production per month for a 10kW system in each city. This monthly energy production directly correlates to the peak sun hours available in that location. Higher monthly energy values indicate more peak sun hours and better solar potential for your investment.
Select Cities to Compare
Solar Production Rankings
Annual production for 10kW systems across all service areas
Data Source: NREL’s PVWatts Database
All solar irradiance and energy production data displayed in this tool comes from the National Renewable Energy Laboratory’s (NREL) PVWatts database. This comprehensive database takes into account numerous climate factors that affect solar energy production, including local weather patterns, atmospheric conditions, temperature variations, and seasonal changes.
The PVWatts system uses decades of meteorological data and sophisticated modeling to provide accurate estimates of solar potential across thousands of locations. This ensures that the peak sun hours and energy production figures you see reflect real-world conditions rather than theoretical maximums, giving you reliable data for making informed solar investment decisions.