How to estimate peak sun hours without confusing them with daylight

Peak sun hours convert a day’s solar resource into an equivalent number of hours at standard full irradiance. Five peak sun hours does not mean the sun shines at full strength for only five clock hours. It means the day’s total resource equals five hours at that reference level.

Use location and array conditions

Start with a location-specific resource estimate, then account for array orientation, tilt, shade and seasonal change. NREL’s PVWatts is a useful example of a location-aware model. Do not substitute sunrise-to-sunset duration.

Carry uncertainty forward

Use the solar generation calculator with an expected value and a visible conservative/optimistic spread. The output is an early planning screen, not a bankable yield forecast. Use a site survey before buying equipment.