A proposal for generating standard climatic data sets for use in energy rating of photovoltaic (PV) modules is presented which will give a good comparability between different technologies. The current proposal of standard data sets consisting of "typical days" do not give realistic estimates of PV performance and thus is not sufficient as a rating standard. A dataset striking the balance between being significant for any location but does not consisting of too much data is required. A method to generate such a dataset is presented, meeting all the requirements of an international standard while being sufficiently accurate to differentiate between different devices of different manufacturers. It is suggested to work with annual data-sets for specific climatic zones, and compare devices based on their module performance ratio. Using geographical information systems and proven modeling approaches, it is demonstrated that seven such annual data sets give sufficient detail and relevance to allow a comparison of different PV device technologies in all European operating environments. The method to use GIS datasets to identify suitable sites and then use more accurate, specific measurement data based on long-term averages for chosen sites. It is shown that the year-to-year variation is minimal, thus making these datasets suitable for comparing typical energy yields of different devices, i.e. carry out an energy rating. The study is currently limited to European data and climatic zones, which is sufficient to derive the methodology for generating and classifying the data. An international standard will, however, need a wider coverage. The extension to other data-sets and climatic zones is proposed and will have to be carried out by the appropriate standards bodies if this is to become an internationally accepted standard.