More and more frequently unit combined hear and power plants (BHKW) are employed in communal industrial and commercial enterprises which are to enable the supply with electric and thermal useful energy so that the operational cost resulting from this are minimized. With greater energy supply enterprises (EVU) there exist for such tasks optimization programmes on large-scale computer systems. Such system solutions are nor realizable especially for operators of plants of a smaller scale, because of the cost of purchase and the maintenance costs. Over and above that, they contain bl general options, which are either not necessary or do not suit the needs of a smaller or medium-size supply enterprise. In the following is shown, how cost-effective, PC-technology-aided programme systems for rile unit combined heat and power plant-application optimization can be developed in dependence on the actual economic framework conditions of the enterprise.