Energy storage is a major lever for the energy transition. It makes it possible to develop the production of energies with low CO2 emissions and to ensure the supply of energy to consumers at all times. So far, the most economic and efficient way to store energy in large quantities is to store it in the form of gas injected into underground reservoirs. A key player in the natural gas market, ENGIE has a storage capacity of more than 136 TWh in Europe, the equivalent of the annual energy needs of more 30 million electric vehicles. The underground storage activities are led by Storengy, a 100% subsidiary of the ENGIE Group. Storengy is the leading storage operator and the leading marketer of energy storage capacity in France and Europe, with its 21 industrial sites: 14 in France, 6 in Germany and 1 in the United Kingdom.