Given an incident irradiance metric with units of W/m² for each array, find the weighted average of the irradiance on N DC arrays, each with M_i modules of different area A_i. The area is calculated using the length and width of the modules per the module definition.

The same formula can be applied to all irradiance measurements, whether irradiance after shading losses, irradiance after soiling losses, effective irradiance, etc.