In order do trigger the transition to the high confinement mode (H-mode), the power lost through the separatrix into the Scrape-Off Layer (SOL), PL, estimated as the sum of the Ohmic and auxiliary heating power from which the time derivative of the plasma stored energy is substructed, should exceed some threshold value Pth. A simple scaling for Pth has been deduced from the experimental data collected on several tokamaks with divertors.