Résumé : Using complementary currencies systems as policy instruments for environmental purposes is a trend that seems to be progressively emerging in Europe. The Belgian Science Policy INESPO Project , in the framework of which the research presented in this paper was carried out, is building on this emerging trend. The aim of the INESPO project is indeed to build new instruments for energy saving policies in the household sector based on the innovative coupling of Complementary Currencies (CC) and Smart Meters (SM). This CC-SM instrument is intended to promote both behavioural changes in everyday life and investment decisions leading to increased energy efficiency. In order to gain insights for the design of the CC part of the instrument, a first step was to turn to projects that had already used in the past CC as policy instrument for behavioural change. Two projects (NU-Spaarpas and E-portemonnee) that have pioneered this path in Europe were analysed to this purpose. This analysis revealed that, although those two projects had not been left unnoticed by academics, no taxonomy of their constitutive parameters had been developed yet. This paper is intended to contribute to the research on CC as policy instrument for environmental sustainability by proposing such a taxonomy for those CC projects. The resulting hierarchical classification of parameters has already been tested as a building tool during the design phase of the INESPO project. In the process, it became evident that the conceptual frameworks used to understand and explain behaviours had a major impact on the design of the CC-SM instrument and could lead to very different choices for key parameters of the system.