The need to reduce human environmental footprint has encouraged the development and use of innovative lighting systems that are becoming “smart” and more efficient in terms of energy use and/or service life. These novel systems are based on Solid State Lighting devices and more especially on light-emitting diodes (LEDs) technologies. However, beyond energy consumption or carbon footprint, there are many other criteria that must be taken into account when evaluating which light systems should be preferred depending on the situation. First of all, the potential environmental impacts generated by the manufacture, use and end of life of a system can be determined through Life Cycle Analysis. This standardized method provides an overview of the impacts of each phase of the life cycle and thus makes it possible to evaluate the performance of different lighting systems. LCA also helps to evaluate the relative effects of each phase of the life cycle on the impacts. These effects depend mainly on how the electricity consumed during use is generated but not only. To fully understand and quantify the impacts in our planet’s “abiotic resources” (energy, materials…) and on our biosphere (biotope and human being) we need define new metrics for quantifying an “appliance efficacy” of a lighting system for a given application. In this context, multi-criteria analysis has proved its worth in facilitating decision-making around complex problems containing many criteria that sometimes contradict. This talk, will stress all these aspects in order to draft the characteristics of what should be the most efficient light system for a given application.