Enter solar access for each month (percent, 0 to 100). The annual figure weights each month by its share of yearly sunlight on the array plane. A design aid: your tool's own annual figure comes from hourly data and is the one to report.
Weights: monthly plane-of-array sunlight (pvlib 0.16.1, Perez model, albedo 0.2). The NSRDB sets use hourly typical-year files for a 25 degree, south-facing plane. The Denver set is the clear-sky model of our shading-analysis example. Another tilt or azimuth changes the weights: paste your tool's monthly irradiance as custom weights.