Observations of localized heat loads to ELM filament impact on the main chamber in JET are reviewed and drawn together to form a coherent picture of the exhaust phase of the ELM. Presently available JET data is quantitatively explained by a parallel loss model of ELM filament dynamics, in which the evolution of filament density and temperature proceeds via a competition of radial advection and parallel convective and conductive losses. The fraction of ELM energy reaching the wall increases with ELM amplitude, in rough agreement with a modified interchange scaling of filamentary motion. The model validated on JET data predicts that ~25% and ~4% of the ELM energy would reach the main chamber (mostly the upper baffle) in ITER for natural (20MJ, DW/Wped ~ 13.3%) and mitigated (1MJ, DW/Wped ~ 0.66%) ELMs, respectively.