A method for summarising annual or seasonal solar irradiation data in irradiation distribution diagrams including both direct and diffuse irradiation is outlined. The practical use of irradiation distribution diagrams is discussed in the paper. Examples are given for the calculation of collectable irradiation on hat plate collectors or trough-like concentrators like the compound parabolic concentrator (CPC), and for the calculation of overhang geometries for windows to prevent overheating of buildings.