This document gives recommended practice for the use of pyranometers in solar energy applications (e.g. testing of solar photovoltaic panels, solar thermal collectors or other devices, and performance monitoring of solar energy systems). It is applicable for both outdoor and indoor use of pyranometers, when measuring plane of array, global horizontal and reflected irradiance, or radiation from a solar simulator. The measurement may be carried out on either a horizontal or an inclined surface, and the pyranometer may be part of a diffusometer, i.e. combined with a sun-shading device to measure diffuse radiation.