The kinetic energy budget over North America is computed for a six day period spanning the pre-storm, growth, and decay stages of an intense cyclone. Regarding this region as comprising the total storm system, the results show that for the total system near balance between conversion of potential to kinetic energy and dissipation of kinetic energy occurs in the lower troposphere. However, in the upper troposphere the import of kinetic energy is an additional energy source which often exceeds the contribution from the conversion process. In addition the strong upper tropospheric flow is accompanied by a maximum in the dissipation. A composite energy budget for the immediate storm vicinity leads to conclusions which are qualitatively similar to those for the storm system, although the storm vicinity is energetically more intense than the total storm system by a factor of about three.