This new investment cycle will constitute a major test for competitive markets and one of the last opportunities to decarbonise the electricity mix by 2050. Many economists, as well as the IEA (2007), recommend well-functioning electricity markets as the efficient solution, provided that prices can rise high enough during periods of scarcity, and that there is a stable regulatory framework. Yet a growing number of countries have recently adopted new rules mandating system operators to contract for generation capacity (New Zealand, Ontario, California, Norway and Sweden) or have introduced explicit margin or capacity targets (PJM, Italy, Australia's eastern states and Latin America).