Energy markets are undergoing major change. They have to cope with a new economic environment and, at the same time, a new energy context. Indeed, on the one hand, energy markets are undergoing deregulation with the aim of opening them to competition. They are also submitted to priva-tisation policies, which progressively detach them from the government’s hold. This trend is transforming the market structure and might particu-larly modify operators’ behaviour and strategies. On the other hand, energy markets face new environmental constraints. Indeed, fossil fuel resources, such as oil, coal, and gas, which are still widely used today, are highly polluting and largely contribute to the greenhouse effect. Moreover, they are getting scarcer and scarcer because their world reserves are running short. Therefore, under the Kyoto Protocol regime, the question of future energy sources arises with acuteness today.