Calculations of cycle processes cannot be dispensed with in the test operation for the preparing and accompanying balancing of materials and heat flows for a meaningful interpretation of the test results and for the interpretation of power station processes. The advantages and the efficiency of a thermodynamic calculation programme are presented int eh following. As examples the calculations of the heat balances for two test plants on the college of technology scale, as well as the thermodynamic interpretation of a combined gas steam turbine cycle with circulating pressurized fluidized bed combustion are described.