Overview on heat loads in the LHC

A consequence of the formation of electron cloud in beam chambers is the deposition of energy on their walls due to electron impacts. In cryogenic devices this can cause a significant heat load for the cryogenics system, posing constraints on machine design and operation At the LHC this effect is found to be quite strong and needs to be addressed to avoid performance limitations in view of the planned HL-LHC upgrade. Unexpectedly the eight LHC arcs show very dierent heat loads. These differences, which appeared after the 2013-14 shut-down period, are still unexplained and have been the subject of thorough investigations and characterizations. This contribution describes the main observations on the heat loads deposited on the arc beam screens with different beam conditions and in dierent moments of the LHC operational experience.