HOMER Pro 3.9
Global Horizontal Irradiance is the total solar radiation incident on a horizontal surface. It is the sum of Direct Normal Irradiance (DNI), Diffuse Horizontal Irradiance (DHI), and ground-reflected radiation. HOMER uses Solar GHI to compute flat-panel PV output.
See also
Image source: RReDC Glossary of Solar Radiation Resource Terms, NREL Renewable Resource Data Center from http://rredc.nrel.gov/solar/pubs/shining/images/pg12.gif
