Abstract The competitiveness of nuclear power in a power system with a substantial amount of coal-fired combined heat and power (CHP) is discussed using the expectedstructure of the Danish power system at the beginning of the next century as an example. The system efficiencies for CHP production are analysed, the structure of two simulation models is described, and the net savings of each marginal nuclear unit are calculated. The results are presented as probability distributions of the net savings taking into account the uncertainties of selected parameters. The method may be used for other very capital intensive power producing technologies.