Many factors influence the choice of the electrical power generation system and the design of the associated busbar distribution network in an aircraft. Beyond the usual factors of safety, initial cost, weight, maintenance cost and the actual rating, the characteristics of the electrical power demanded by the utilisation system, and in particular the avionics equipment, are becoming a factor of increasing importance. The influence of such systems will, of course, vary with the aircraft size, its role, and its overall complexity. Perhaps it is as well also, to point out that the purpose of any system is to enable the aircraft to fulfil its role in the most cost effective manner. This may be a novel approach to the systems engineer whose enthusiasm leads him to believe that the aircraft's sole purpose is to carry around his pet system.