The paper reviews some recent approaches towards measuring the extent of long-term energy security and security externality valuation. It starts out to discuss the contextual connotations of notions of 'energy security' in medium to long-term time frames and reviews some indicators that have been proposed to quantify it. Special attention is paid to two of these approaches, which the authors helped to develop, i.e. diversity-based indices and the Supply/Demand Index. The paper takes issue with conventional welfare economic approaches that neglect: (i) the scope on the demand side for raising security and (ii) negative feedback mechanisms of socio-political impacts of international rent transfers in fossil fuels exporting countries. The concept of energy services security is proposed with a demand-side focus. This enables application of an integrated approach to gauge the resilience of a society to meet the needs of its population for energy services over longer timescales ahead from various interrelated perspectives. Propositions are made on the attribution of security externalities to the use of fossil fuels, policies, and suggestions for further improvements of measures for energy services security. (C) 2009 Elsevier Ltd. All rights reserved.