The paper presents the results of thermal investigations and calculations of the influence of the operational parameters of chamber furnaces on the loss of heat to the environment and the consumption of the chemical energy of fuels per unit of charge. The least squares adjustment method to coordinate the substance balances has been used. Energy balances have been set up basing on the enthalpy of devaluation. By means of the analysis of the stepwise regression method the empirical functions were determined. The results obtained will be applied in the algorithm for controlling the operation of furnaces.