Irradiance

Irradiance is the rate of solar energy reaching a surface, usually expressed in watts per square metre (W/m²). In home solar documents it describes how much sunlight reaches a roof plane, PV module or array at a particular time. PVGIS uses in-plane irradiance when estimating hourly PV output, and MCS shading material uses potential irradiance to describe sunlight that could be blocked by nearby objects. Irradiance is not the same as accumulated irradiation, annual generation, kWp, shading, roof orientation, export capacity, DNO acceptance or proof that a system will meet a quoted output.