Abstract: To date, all kinds of power meters and watt-hour meters installed at electrical node gateways can only measure and count the total power and total energy of each line entering or leaving a node. These meters cannot obtain the information regarding the power interaction and energy distribution between electrical sources and flows. This situation may hinder the fair accounting and allocation of cost for energy usage. This paper extended the node proportional sharing theorem for instantaneous current to the application of instantaneous power. The formulas for calculating instantaneous power interaction or crossing between any two sources and between any two flows, and the instantaneous power transmitting and accepting between any one pair of sources and flows were first derived. Then, numerical and analytical methods for calculating the energy distribution relationship of nodal sources and flows in one cycle were proposed, and the corresponding energy distribution matrices were also designed to signify the acceptance relationship among all source-source pairs and flow-flow pairs and source-flow pairs of the same node. Finally, the results of energy distribution matrices of an example for energy supply of a node were provided and we also compared these results with other existing methods. The study of this paper shows the proposed method will provide theoretical support for the development of a new type of smart meter or for energy and cost accounting at the node gateway.