PV Fast Facts

It’s relatively easy to estimate the amount of annual output from a solar photovoltaic (PV) system, its comparative price with other solar systems, and its economics in terms of cents per kilowatt-hour (c/kWh).

Local Sunlight

Local sunlight is an important factor in the output and economics of a solar PV system. Electric output is essentially proportional to the amount of local sunlight, and cost is inversely proportional to output.

US Sunlight on a module at latitude tilt

US Sunlight on a module at latitude tilt (kWh/m2-day)

Solar maps are a good source of local sunlight. Here is one from NREL for the US, showing sunlight available for a fixed array pointing south at a tilt equal to its latitude, about optimal for such designs. You need a different map for one- and two-axis trackers for flat plates; and another one for concentrating trackers, which use only a portion of the light. But most installations are simply fixed tilt; or, in a few cases, large systems use single-axis trackers. (more…)