The magnetic energy balance and magnetic energy flows for plasma disruptions in which runaway plateau plasmas are formed and terminated at JET has been analysed and compared with that of runaway-free disruptions. The analysis shows that the energy loss processes during runaway plateau plasma termination are qualitatively different from those of a runaway-free disruption because of the pre-existence of a runaway population in the first case. As a consequence, a significant fraction of the runaway plateau plasma magnetic energy is directly converted into runaway electron kinetic energy during the runaway plateau termination phase. This leads to the fluxes being deposited by runaway electrons onto in-vessel components during the termination of runaway plateaus to be significantly larger than those expected from the initial kinetic energy of the runaway electrons in the runaway plateau plasma.