What is Insolation?
Insolation is a measure of (solar) radiation on a particular surface or area, and is expressed in W/m2. In other words, it can be a measure of how strong the sun is in a particular geographic area. Insolation is strongest when the angle of incidence (of the sunlight) to the panel is 90 degrees. Insolation becomes lower with decreasing angle of incidence – this is because the light rays are spread across a wider area and are more diffuse. Less radiation is incident on the panel per square meter, meaning less power will be produced. Insolation is also called irradiance.
