A binding target for sustainable energy demand: Why and how?

On January 22nd, 2014, the European Commission published its proposal for a policy framework for climate and energy in the period from 2020 to 2030. The current paper complements the eceee comment on this proposal by discussing the following issues:
what targets are, and their main pros & cons;
why a binding target for sustainable energy demand is needed;
the various options to set and monitor this target.
In this paper, we speak of a target for sustainable energy demand, which is meant to encompass the different possibilities of targets expressed in terms of energy efficiency improvements, energy savings or maximum level of energy consumption. The term “sustainable” is used to highlight that the roadmap towards 2050 means that the objectives of reducing the GHG emissions by 75 to 80% (compared to 1990) cannot be achieved in a sustainable way without reducing the energy demand. The 2050 roadmap mentions a level of consumption 30% lower than 2005.