It is found that in electron resonant tunneling via localised states, the current exhibits a very strong temperature dependence and power nonconservation. This subtle behaviour is due to the impurity states induced tunneling which is subsequently renormalised by an overlap integral of many-electron states in the emitter. By using a temperature-dependent dynamical approach, an analysis of this interesting tunneling process is performed. It is found that the temperature dependence of the current has a very different origin from the thermal activation. It is also found that plasmon excitation in the emitter further renormalises the tunneling current by a factor of two to three orders of magnitude.