A list is provided in this guideline of the physical, energy- and system-related terms which are important in the C.H.P. field. On the basis of this, decisions will preferably be made which should make clear which installations, systems and system technologies should be classed as coming within the field of coupled energy generation or conversion. Efforts are made to obtain the most comprehensive description possible and combined systems of energy conversion which include a serial conversion or application chain are included. The guideline deals on the one hand with the various ways in which C.H.P. is applied as a function of the plant technology and of the energy carriers used and on the other hand with consumer characteristics. Finally, in order to demonstrate the wide variety of C.H.P. installations, a number of systems are listed which are to be classed under combined heat and power. Subsequent parts of the guideline will deal with the various methods used for allocation and assessing the efficiency of the coupled generation or conversion of different target energies. These parts will also be concerned with application of the methods to processes and will show, with the aid of system comparisons, the special characteristics of the C.H.P. installation as compared with other technologies for efficient utilization of energy.