NABCEP PV Installation Professional 2025 – 400 Free Practice Questions to Pass the Exam

The unit used to express solar irradiation is best represented by the measure that quantifies solar energy received over a specific time and area. In this context, the correct unit is kWh/m², which indicates the amount of solar energy (in kilowatt-hours) received per square meter over time, typically measured on a daily or annual basis. This is crucial for understanding how much solar energy a particular area receives, informing decisions on system design and energy production estimates.

The other options represent different measures that are not specifically suited for solar irradiation. kW/m² refers to the power density at a specific moment, which does not provide the cumulative energy received over time. W/m² expresses instantaneous solar power but lacks the time component needed for a complete understanding of the energy available. J/m² indicates joules per square meter, which is a measure of energy but is not commonly utilized in solar energy contexts as kWh/m² is, given that kWh is a more practical unit for evaluating energy generated or consumed over time.