It is necessary for the reduction of energy consumption in a hybrid-type hot water heating unit to estimate the hot process energy state. A model of the process has been suggested, which takes into account both the water consumption and the hourly solar radiation diagrams. The underlying dependences and approximations applied to the modeling have been grounded. The main advantage of the model is in its capability to estimate the current state of the process according to the on-line data provided by sensors, as well as to assess it based on the water consumption diagrams and hourly solar radiation values.
