Once you have prioritized your municipal sites for solar, you can roughly estimate the solar capacity (in kilowatts [kW]) and energy (in kilowatt-hours [kWh]) production potential by using free software such as NREL’s System Advisor Model (SAM) or PVWatts
Estimating Solar PV Potential:
NREL’s PVWatts online tool and System Advisor Model can assess the solar energy potential of rooftops as well as neighboring parking lots and land areas. . SAM is a detailed program that determines the capacity and energy of a solar system by taking into account solar tilt, ground cover ratio, and type of PV module. PVWatts, on the other hand, is a simpler online tool that estimates the capacity and energy available from a user drawn area at a specified location. A quick rule of thumb for rooftop solar is that roughly 70% of a roof can be utilized for solar panels, of which it takes about 100 ft2 (using flat panels) to 150 ft2 (for panels in tilted racks) to reach a capacity of 1 kW. For ground-mounted systems, five acres of land is typically needed to reach a capacity of 1 MW (220 ft2 per kW).
Next, refine each site’s system capacity based on these two important local regulations: