Clearing the Conceptual Jungle of Energy Statistics: Definitions for a Decarbonized Power System

The transition towards a decarbonised, electrified energy system challenges the statistical foundations on which policy, regulation, and research rely. Established indicators such as the renewable energy quota were designed for centralised, fossil-fired power plants, with negligible prosumer activity and limited storage. High shares of variable renewables, increasing rooftop photovoltaic deployment with self-consumption, and diverse storage technologies now fundamentally challenge legacy methods. European legislation has fixed the gross principle and gross inland electricity consumption as the denominator for the renewable energy quota, yet widely cited national indicators deviate systematically from EU-compliant calculations and suffer from double counting in the treatment of pumped hydro storage. To address these ambiguities, we present a Compendium of Statistical Definitions for Electricity Production and Consumption. The compendium provides unambiguous definitions, explicit accounting formulas, and references to exact data series and legal sources for key quantities including gross and net electricity production and consumption, self-consumption, storage balance, and the renewable energy quota. We discuss three main implications: the growing statistical importance of prosumer self-consumption, the comparability of renewable energy quotas across methods and jurisdictions, and the need to exclude pumped hydro storage - and, by extension, other storage technologies - from generation accounting to avoid double counting. The compendium provides a reference layer for harmonising heterogeneous datasets, supports machine-readable term definitions compatible with the Open Energy Ontology, and contributes to future-proof energy statistics for high-renewable energy systems.