Experts agree that renewable energies have an increasing role to play in the global energy sector. Consequently, it is important to assure that the policies implemented to foster their deployment are sustainable. This thesis evaluates the sustainability of the Swiss Feed-in Tariffs scheme using a list of trans-disciplinary principles developed by ecological economists. The evaluation is based on a comparison between the policy chosen in Switzerland (price-based) and the one chosen in the United Kingdom (quantity-based). The thesis concludes that all in all the policy implemented in Switzerland is more sustainable than its British counterpart. It is particularly superior in terms of its ecological effectiveness, influence on social discrepancy and adaptation capacity to changing conditions. However, in the course of the analysis, the necessity to develop new trans-disciplinary principles that would be more concrete and thus easier to apply became apparent.