Peak sun hours are the equivalent number of hours per day when solar irradiance averages 1,000 W/m², the standard testing condition for solar panels. This metric simplifies energy production calculations by converting variable daily irradiance into equivalent hours of peak intensity. Peak sun hours differ from actual daylight hours and vary seasonally and by location.
Technical Details
A location receiving 20 kWh/m²/day insolation has 5 peak sun hours because 1,000 W/m² × 5 hours = 5 kWh/m². Peak sun hours account for the sun’s varying angle throughout the day, morning and evening lower intensity, and atmospheric effects. Most U.S. locations average 3.5-5.5 peak sun hours daily, with southwestern regions reaching 6-6.5 hours. Winter peak sun hours can drop to 2-3 hours, while summer months may reach 7-8 hours in southern climates.
Practical Significance
Peak sun hours enable simple system output calculations: system wattage multiplied by peak sun hours equals daily energy production. A 10kW system with 4.5 peak sun hours produces 45 kWh daily. This straightforward calculation helps homeowners understand system performance and validate actual output against projections.