For solar panel inspections, which phrasing correctly states the minimum irradiance requirement?

• A. A minimum of 1000 W/m^2
• B. A minimum of 400 W/m^2
• C. A minimum of 600 W/m^2
• D. A minimum of 800 W/m^2

Answer: (C)

When inspecting solar panels, you need enough light to bring the modules into a representative operating state so that electrical output and heat patterns are meaningful. The minimum around 600 W/m^2 strikes a balance: it’s high enough to produce detectable current and temperature differences for reliable measurements, yet low enough to be achievable under typical field conditions, not just at peak sun.

If irradiance were much lower, say around 400 W/m^2, the electrical signal becomes weak and thermal contrasts can be overwhelmed by ambient conditions, making it hard to distinguish real issues from normal variation. Higher levels, such as 800–1000 W/m^2, would work, but they’re not the minimum requirement—the question focuses on the smallest level that still yields reliable results.