The analysis of energy system transitions is mainly affected by a socio-technical system (STS) understanding, focussing on the co-evolvement of societal and technical changes. However, energy systems are highly dependent on and characterised by ecological ressources, which are not explicitely considered in the STS approaches. Concept: 1. Integration of the multi-level-perspective (MLP) (Geels 2002) as an analytical approach on STS and the socio-ecological systems framework (SESF) (Ostrom 2009). 2. Conceptualisation of energy systems as integrated socio-ecological technical systems in transition towards sustainability - considering technical & ecological aspects. Expected outcomes: - The STS & the SES perspective share a similar understanding on the consitution of a system through the interaction of system artefacts, rules & the actors (SRA). - The MLP contributes the technical system aspects, the dynamic transition perspective and has frequently been applied to energy systems in transition. - The SESF delivers the ecological system aspects, the preservation of system functionality and an inidcatorset for empirical analysis. - The integration of the MLP and the SESF provides the basis for the conceptualisation of energy systems as SETS based on the interaction of SRA. - The conceptualisation allows for the analysis of the role of actors for systemic transitions considering technical and ecological aspects.