Security of Electricity Supply (SoES) has become a major concern for regulators and policymakers over the last decade. However, most work focusses either more generally on energy security or on a single fuel. We develop a comprehensive but flexible framework to assess the SoES for a single jurisdiction, taking into the account the specificities of electricity. This framework has two aims: (i) provide a snapshot of the situation to understand current weaknesses and determine what actions are required; (ii) capture the evolution over time to evaluate progress and identify potential problems before they materialise. The framework, based on an extensive literature review, consists of twelve dimensions that are critical for SoES. We develop metrics that capture the state and evolution of each dimension. This framework is intended to be a management information tool for all stakeholders, aimed at organising data and structuring its analysis, to enable monitoring the evolution of the SoES, while also functioning as an early-warning system by flagging potential future problems.