predominantly in decentralized settings located close to consumers. This creates a shift in the energy sector toward decentralized (or distributed) generation with smaller production units (Alanne & Saari, 2006). The primary challenge of using renewable energy technologies, such as wind and solar PV, is their highly intermittent and weather-dependent power output. Therefore, to match generation with load, additional measures for flexibility and balance are required. Such improvements can be provided by decentralized systems, 1 which employ multiple energy carriers 2 in combination with conversion and storage technologies. These combinations allow surplus renewable energy to be stored and converted between different carriers, which can help balance load with demand and thus offer additional flexibility in energy management.Systems of this type have been explored under a broad range of names in various literature publications, which focus on different theoretical and societal concepts (, numerous implementations of such systems already exist and can be observed in practice. After reviewing these energy systems, we have found the gap in the research to be twofold. On the one hand, the extant literature lacks a comprehensive overview of the current state of research on decentralized energy systems combining renewable energy technologies with both conversion and storage technologies. The absence of a systematic literature review can also be attributed partially to the lack of common terminology. On the other hand, it remains unclear what kind of systems are implemented today because current project developments have not yet been thoroughly analyzed and described. Pilot projects provide valuable insights into potential future applications as well as practical experiences and challenges. Therefore, this study aims to fill these gaps by providing an extensive review of the current state of literature and practice for renewable energy sources (RES)-based decentralized energy systems with energy conversion and storage.This work is the first to analyze both literature and practice side-by-side, and to review a broad sample of publications and pilot projects. Our systematic overview of the academic literature is complemented by a database of pilot projects, which includes projects in operation as well as those in the planning stage. We compare literature and projects according to relevant thematic fields to determine general trends and patterns across fields. This study reviews decentralized energy systems across a wide range of application (residential, commercial, island, utility) and scale (tens of kilowatt(s) (kW) to megawatt(s) (MW)). Although the extant literature is multifaceted, three required characteristics limit the technological scope of this study to systems that provide: (a) at least one renewable energy technology, (b) conversion device(s), and therefore multiple energy carriers, and (c) energy storage device(s). | MATERIAL AND METHODSThis section starts by introducing the main categories used to review and an...