
Here is a solar irradiance map of the United States provided by the National Renewable Energy Laboratory: And here is a global solar irradiance. . I’ll run through 3 more free tools for calculating solar irradiance for your location: 1. Global Solar Atlas 2. PVWatts Calculator 3. National Solar Radiation Database Viewer Let’s. . Sometimes, you’ll see solar radiation data expressed in peak sun hours. Solar insolation and peak sun hours both express how much solar. . Solar irradiance is an instantaneous measurement of solar power over a given area. Its units are watts per square meter (W/m2). Solar insolation is.