Ground Coverage Ratio
The ground coverage ratio (GCR) applies only to arrays with one-axis tracking, and is the ratio of module surface area to the area of the ground or roof occupied by the array. A GCR of 0.5 means that when the modules are horizontal, half of the surface below the array is occupied by the array. An array with wider spacing between rows of modules has a lower GCR than one with narrower spacing. A GCR of 1 would be for an array with no space between modules, and a GCR of 0 for infinite spacing between rows. The default value is 0.4, and typical values range from 0.3 to 0.6.
PVWatts® uses the GCR value to calculated losses due to shading of neighboring rows of modules in the array.