The multidimensional character of renewable energy sources (RES) necessitates the collection of a number of related data in order to support EU policy needs. Apart from the technology and technophysical data also socioeconomic (e.g. employment, turnover) data and R&D expenditures are of critical relevance. The monitoring of the above RES data with respect to the existing targets for RES is of significant importance. In addition to this, even though significant data gathering efforts have been implemented, a lot of fragmented data and deduced findings are currently available, which sometimes lack consistency and verification. As a result, RES data validation and completion capacity is needed in the framework of the European Union (EU) energy policy. In addition to this, agreed and validated RES data can help energy policy makers and relevant stakeholders answering to pressing energy socio-economics' and sustainability issues. In this context, the main aim of the paper is to present a reference methodology for validating the RES Data in the EU. The development of the methodology is mainly based on the review of existing methods and ends up with recommendations for improvements in RES data aggregation and statistical interpretation, taking into consideration the related analysis of statisticians, energy technology experts and energy socio-economists. (c) 2006 Elsevier Ltd. All rights reserved.