Alarming reports alert us every day that our relationship with the planet is suicidal. The acceleration of the cost of energy makes us aware of its preciousness.Scientific calculation has been racing to solve ever more complex problems, and we owe it a lot. It is time to introduce the energy criterion into optimization, to move from a time-to-solution paradigm to an energy-to-solution one.IT infrastructures managed by information systems departments (ISDs) now give us access to almost infinite resources, both locally and in the cloud. But the real costs of these infrastructures are starting to emerge (hardware manufacturing), and the cost per kWh announced in the coming years will force us to change our paradigm and integrate energy efficiency into software solutions.How can we just sit back and watch?It is time to make the use of IT infrastructures more efficient