Energy market liberalization and international economic interdependence have affected governments’ ability to react to security of supply challenges. On the other side, whereas in the past security of supply was largely seen as a national responsibility, the frame of reference has increasingly become the EU in which liberation increases security of supply mainly by increasing the number of markets participants and improving the flexibility of energy systems. In this logic, security of supply becomes a risk management strategy with a strong inclination towards cost effectiveness, involving both the supply and the demand side. Security of supply has two major components that interrelate: cost and risk. This paper focus the attention on costs in the attempt to develop a market compatible approach geared towards security of supply.