A comparison of economic data for different technologies and fuels is difficult due to the number of parameters that can alter the profitability of heat and power production. In addition, the variation of currency exchange rates considerably reduces the possibility of comparing plants in different countries. In the present study, a new method based on dimensionless costs is proposed to overcome these difficulties. Dimensionless capital costs C (including maintenance) and dimensionless fuel costs F are introduced by dividing the costs by the price for heat or electricity. In a diagram of C versus F the economy of different technologies can be compared. The diagram is divided into a profitable and an unprofitable area. The orientation of the data from one specific plant shows immediately whether the plant can be operated economically or not. Furthermore it can be seen by which factor either the fuel costs have to be reduced, or the price for electricity or heat has to be increased, or the capital and maintenance costs have to be reduced to leach the profitable area. The dimensionless diagram is independent from currency exchange rates. To demonstrate the application of the method, data from an economic assessment study of power production plants from biomass using pyrolysis, gasification and combustion technologies are presented. (C) 2000 Elsevier Science Ltd. All rights reserved.