Sector coupling reimagined: Synthesizing fragmented perspectives into a unified framework

Sector coupling (SC), the integration of energy vectors and end-use sectors, is increasingly central to the net-zero transition but remains conceptually fragmented. This fragmentation causes modeling inconsistencies, hinders cross-study comparison, and undermines energy policy coordination. We address this gap through a structured mapping of existing definitions, categorizing them along three dimensions, namely, structural, functional, and electricity-centric, and analyzing their limitations. Drawing on these insights, we propose a coherent definition that captures SC in its full diversity and complexity: SC is the establishment of physical or non-physical interconnections, in any direction, among energy-carrying vectors, among energy-consuming end-use sectors, between vectors and sectors, and within the layers that link them (energy processing, transfer, markets, and policy). This framing clarifies what constitutes a “sector”, distinguishes “sector coupling” from related concepts such as “flexibility”, and encompasses the entire spectrum of interlinkages in a sector-coupled energy system. Building on this definition, we organize the SC interlinkages into six categories based on their driving mechanisms: vector coupling, end-use sector coupling, vector-shift coupling, network coupling, market coupling, and policy coupling. Together, our definition and classification provide a shared conceptual foundation for the SC field. The framework’s modular architecture enables extension to new end-use sectors, non-energy material flows, and material-energy circularity pathways. It can enable modelers to avoid unintentional mismatches in model scopes, standardize SC implementation in models, and trace cascading, system-wide interactions. It can also support policymakers in designing structured scenarios, identifying which SC pathway works best in specific settings, and coordinating cross-sector cross-vector policies. By synthesizing fragmented concepts into a coherent and comprehensive whole, this work advances the theory of the SC domain.