This Codex EU Energy Law brings together the most important, presently applicable, legislation on energy, as adopted by the EU. The legislation has been booming in recent years, after decades of very limited European activity in the field, with the exception of coal and nuclear. Several drivers explain this increase: the liberalisation of the European gas and electricity markets, the awareness to improve the security of energy supply, the necessity to be more energy-efficient, and the protection of the environment. All this has been translated in several, recent (i.e. 2009/ 2010) legislative energy packages: the liberalisation package, the climate and energy package, and the energy efficiency package. As a consequence, a serious amount of new regulations, directives and decisions on gas, electricity, renewables, biofuels, regulators, appliances, buildings, etc. must be implemented and/or applied by the Member States. Practitioners and academics will find this codex to be a good working tool.