This International Standard gives the basic concepts needed to define and describe technical energy systems. It introduces the concept technosphere and its division into two sectors. The economic purpose of one of these is to supply the other with energy in the technical-economic sense, i.e. energyware, to be distinguished from energy in the physical sense. The items included in that concept are given in a closed list. The standard prescribes the input- output model and the consolidation principle applied to technical energy systems. The outputs from the model are the intended product or service, the releases from the technosphere to nature, the use of natural resources and the associated exploitative impacts.