This paper discusses how the deceleration of economic growth, that followed the financial crisis of 2008, influenced the energy efficiency, allocation and use of 18 European countries. By using a Multi-scale Integrated Analysis of Societal and Ecosystem Metabolism (MuSIASEM), the relationships between energy requirements, economic trends and population are investigated for the years 2008 and 2015. The analyses are performed for the entire society (Level N), for the household and the paid sectors (Level N-1) and for the agricultural, the industrial and the service activities (Level N-2). Results show that two main groups of countries performed the largest energy reductions, namely: the country most affected by the global financial crisis, such as Greece, Romania and Spain, where the total energy throughput decreased by −19.6%, −15.8% and −12.1%, respectively; and the countries, such as Ireland and United Kingdom, that experienced the largest energy intensity reductions (−38.7% and −19.2%), together with the highest GDP increases (+44.8% and +10.2%). By providing an overview of the relationships existing between socio-economic and energy variables, this paper contributes to the debate around growth and efficiency and can support the design of policies oriented to promote the achievement of a more sustainable and competitive economy.