The trajectory outlined in the Paris Agreement to keep global warming below 2°C dictates not only the timing but also the speed at which the transformation of our energy system must take place to decarbonize energy production. Complying with the Paris Agreement requires reducing the carbon content of energy by about 75% and therefore making a rapid transition from fossil production to production based on low-carbon technologies. Among these technologies are those based on renewable energies. The variability of the climate itself induces a fluctuating or even an intermittent production of variable renewable energy (solar, wind, marine), challenging the balance of the electricity grid. In this context, to speak of energy transition is to face the problem of increasing the penetration of low-carbon energy production while limiting the variability while ensuring socio-technical feasibility and economic viability. The problem is not simple and the delicate balance between urgency (drastic reduction in emissions) and utopia (what strategy for low carbon energies, opportunities and obstacles) needs to be clearly defined.