Transforming energy systems to fulfill the needs ora low-carbon economy requires large investments in renewable electricity production (RES-E). Recent literature underlines the need to take a closer look at the composition of the RES-E investor group in order to understand the motives and investment processes of different types of investors. However, existing energy policies generally consider RES-E investments made on a regional or national level, and target investors who evaluate their RES-E investments according to least-cost high-profit criteria. We present empirical evidence to show that RES-E investments are made by a heterogeneous group of investors, that a variety of investors exist and that their formation varies among the different types of renewable sources. This has direct implications for our understanding of the investment process in RES-E and for the study of motives and driving forces of RES-E investors. We introduce a multi-dimensional framework for analyzing differences between categories of investors, which not only considers to the standard economic dimension which is predominant in the contemporary energy literature, but also considers the entrepreneurship, innovation-adoption and institutional dimensions. The framework emphasizes the influence of four main investor-related factors on the investment process which should be studied in future research: motives, background, resources and personal characteristics. (C) 2013 Elsevier Ltd. All rights reserved.