The article discusses the relationship between the heat flow and the power supplied to a test object. Often, it is reasonable to say that the heat flow and power are correlated. Intuitively, one can assume that knowing the distribution of the heat flow in time permits to determine the power of a system. Such a statement is valid in some cases. In order to determine fault assumptions an experiment was carried out. The object of research was chosen so as to simplify the physical model of the experiment. The goal of the experiment was to study the heating power of systems consisting of tubes filled with water. The signal was recorded using thermistors and a thermal imaging camera. The analysis of the results shows that there is a strong relationship between the power supplied and temperature increase. Information on energy dissipation of a system is characterized by medium and small average error, thus, allows the evaluation of a machine’s performance.