The power and energy requirements of the Joint European Torus (JET) are described. The problems involved in supplying such a load from the H. V. lines adjacent to the proposed JET sites are discussed and a cost comparison is made between the two possible components of the power supply, i. e. flywheel. generator-convertors and transformer-controlled-convertors. The proposed JET power supply system is described, together with an outline of the power supply control and its relationship with the overall JET control system.